1
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Han ML, Alsaadi Y, Zhao J, Zhu Y, Lu J, Jiang X, Ma W, Patil NA, Dunstan RA, Le Brun AP, Wickremasinghe H, Hu X, Wu Y, Yu HH, Wang J, Barlow CK, Bergen PJ, Shen HH, Lithgow T, Creek DJ, Velkov T, Li J. Arginine catabolism is essential to polymyxin dependence in Acinetobacter baumannii. Cell Rep 2024; 43:114410. [PMID: 38923457 DOI: 10.1016/j.celrep.2024.114410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 02/03/2024] [Accepted: 06/12/2024] [Indexed: 06/28/2024] Open
Abstract
Polymyxins are often the only effective antibiotics against the "Critical" pathogen Acinetobacter baumannii. Worryingly, highly polymyxin-resistant A. baumannii displaying dependence on polymyxins has emerged in the clinic, leading to diagnosis and treatment failures. Here, we report that arginine metabolism is essential for polymyxin-dependent A. baumannii. Specifically, the arginine degradation pathway was significantly altered in polymyxin-dependent strains compared to wild-type strains, with critical metabolites (e.g., L-arginine and L-glutamate) severely depleted and expression of the astABCDE operon significantly increased. Supplementation of arginine increased bacterial metabolic activity and suppressed polymyxin dependence. Deletion of astA, the first gene in the arginine degradation pathway, decreased phosphatidylglycerol and increased phosphatidylethanolamine levels in the outer membrane, thereby reducing the interaction with polymyxins. This study elucidates the molecular mechanism by which arginine metabolism impacts polymyxin dependence in A. baumannii, underscoring its critical role in improving diagnosis and treatment of life-threatening infections caused by "undetectable" polymyxin-dependent A. baumannii.
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Affiliation(s)
- Mei-Ling Han
- Infection Program and Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia.
| | - Yasser Alsaadi
- Infection Program and Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia
| | - Jinxin Zhao
- Infection Program and Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia
| | - Yan Zhu
- Infection Program and Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia
| | - Jing Lu
- Infection Program and Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia
| | - Xukai Jiang
- National Glycoengineering Research Centre, Shandong University, Qingdao 266237, China
| | - Wendong Ma
- Infection Program and Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia
| | - Nitin A Patil
- Infection Program and Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia
| | - Rhys A Dunstan
- Infection Program and Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia
| | - Anton P Le Brun
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia
| | - Hasini Wickremasinghe
- Infection Program and Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia
| | - Xiaohan Hu
- Infection Program and Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia
| | - Yimin Wu
- Infection Program and Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia
| | - Heidi H Yu
- Infection Program and Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia
| | - Jiping Wang
- Infection Program and Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia
| | - Christopher K Barlow
- Monash Proteomics and Metabolomics Facility, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia
| | - Phillip J Bergen
- Infection Program and Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia
| | - Hsin-Hui Shen
- Department of Materials Science and Engineering, Faculty of Engineering, Monash University, Clayton, VIC 3800, Australia
| | - Trevor Lithgow
- Infection Program and Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia
| | - Darren J Creek
- Monash Proteomics and Metabolomics Facility, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, VIC 3052, Australia
| | - Tony Velkov
- Department of Pharmacology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia
| | - Jian Li
- Infection Program and Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia; Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia.
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2
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Groover KE, Randall JR, Davies BW. Development of a Selective and Stable Antimicrobial Peptide. ACS Infect Dis 2024; 10:2151-2160. [PMID: 38712889 PMCID: PMC11185160 DOI: 10.1021/acsinfecdis.4c00142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 04/17/2024] [Accepted: 04/26/2024] [Indexed: 05/08/2024]
Abstract
Antimicrobial peptides (AMPs) are presented as potential scaffolds for antibiotic development due to their desirable qualities including broad-spectrum activity, rapid action, and general lack of susceptibility to current resistance mechanisms. However, they often lose antibacterial activity under physiological conditions and/or display mammalian cell toxicity, which limits their potential use. Identification of AMPs that overcome these barriers will help develop rules for how this antibacterial class can be developed to treat infection. Here we describe the development of our novel synthetic AMP, from discovery through in vivo application. Our evolved AMP, DTr18-dab, has broad-spectrum antibacterial activity and is nonhemolytic. It is active against planktonic bacteria and biofilm, is unaffected by colistin resistance, and importantly is active in both human serum and a Galleria mellonella infection model. Several modifications, including the incorporation of noncanonical amino acids, were used to arrive at this robust sequence. We observed that the impact on antibacterial activity with noncanonical amino acids was dependent on assay conditions and therefore not entirely predictable. Overall, our results demonstrate how a relatively weak lead can be developed into a robust AMP with qualities important for potential therapeutic translation.
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Affiliation(s)
- Kyra E. Groover
- Department
of Molecular Biosciences, The University
of Texas at Austin, Austin, Texas 78712, United States
| | - Justin R. Randall
- Department
of Molecular Biosciences, The University
of Texas at Austin, Austin, Texas 78712, United States
| | - Bryan W. Davies
- Department
of Molecular Biosciences, The University
of Texas at Austin, Austin, Texas 78712, United States
- John
Ring LaMontagne Center for Infectious Diseases, The University of Texas at Austin, Austin, Texas 78712, United States
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3
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Bacon EE, Tran JS, Nadig N, Peters JM. Modular, inducible, and titratable expression systems for Escherichia coli and Acinetobacter baumannii. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.28.596346. [PMID: 38853957 PMCID: PMC11160707 DOI: 10.1101/2024.05.28.596346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
Gene expression systems that transcend species barriers are needed for cross-species analysis of gene function. In particular, expression systems that can be utilized in both model and pathogenic bacteria underpin comparative functional approaches that inform conserved and variable features of bacterial physiology. Here, we develop replicative and integrative vectors alongside a novel, IPTG-inducible promoter that can be used in the model bacterium Escherichia coli K-12 as well as strains of the antibiotic-resistant pathogen, Acinetobacter baumannii. We generate modular vectors that transfer by conjugation at high efficiency and either replicate or integrate into the genome, depending on design. Embedded in these vectors, we also developed a synthetic, IPTG-inducible promoter, P abstBR , that induces to a high level, but is less leaky than the commonly used trc promoter. We show that P abstBR is titratable at both the population and single cell level, regardless of species, highlighting the utility of our expression systems for cross-species functional studies. Finally, as a proof of principle, we use our integrating vector to develop a reporter for the E. coli envelope stress σ factor, RpoE, and deploy the reporter in E. coli and A. baumannii, finding that A. baumannii does not recognize RpoE-dependent promoters unless RpoE is heterologously expressed. We envision that these vector and promoter tools will be valuable for the community of researchers that study fundamental biology of E. coli and A. baumannii.
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Affiliation(s)
- Emily E Bacon
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, WI 53705
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI 53706
| | - Jennifer S Tran
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, WI 53705
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI 53706
| | - Nischala Nadig
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, WI 53705
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI 53706
| | - Jason M Peters
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, WI 53705
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI 53726
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706
- Center for Genomic Science Innovation, University of Wisconsin-Madison, Madison, WI 53706
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4
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Gurnani M, Chauhan A, Ranjan A, Gopi P, Ghosh A, Tuli HS, Haque S, Pandya P, Lal R, Jindal T. Cyanobacterial compound Tolyporphine K as an inhibitor of Apo-PBP (penicillin-binding protein) in A. baumannii and its ADME assessment. J Biomol Struct Dyn 2024; 42:4133-4144. [PMID: 37261797 DOI: 10.1080/07391102.2023.2218930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 05/22/2023] [Indexed: 06/02/2023]
Abstract
Antibiotic-resistant Acinetobacter baumannii, is a common pathogen found in hospital settings and has become nosocomial due to its high infection-causing tendency amongst ICU patients. The present study explores the cyanocompoundswhich were capable to inhibit the Penicillin Binding Protein of A. baumannii through molecular docking, ADMET, and molecular dynamicssimulation strategy. A database having structural and origin details was generated for 85 bioactive compounds in MS Excel. The 3-D structures weredownloaded from the PubChem database and minimized. The receptor protein was minimized and validated for structure correctness. The database was screened against the penicillin-binding protein of A. baumannii through PyRx software. The top 5 compounds including the control molecule werefurther redocked to the receptor molecule through Autodock Vina software. The molecule pose having the highest affinity was further subjected to 100ns MD- simulation and simultaneously the in-vitro activity of the methanol extract and hexane extract was checked through agar well diffusion assay.Docking studies indicate Tolyporphine K to be a lead molecule which was further assessed through Molecular dynamics and MM/PBSA. The in-silicoresults suggested that the protein-ligand complex was found to be stable over the 100 ns trajectory with a binding free energy of -8.56 Kcalmol-1. Theligand did not induce any major structural conformation in the protein moiety and was largely stabilized by hydrophobic interactions. The bioactivityscore and ADME properties of the compounds were also calculated. The in-vitro agar well diffusion assay showed a moderate zone of inhibition of12.33mm. The results indicate that the compound Tolyporphin- K could be a potential inhibitor of penicillin-binding protein in A. baumannii. Yet furtherwork needs to be done to have a more concrete basis for the pathway of inhibition.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Manisha Gurnani
- Amity Institute of Environmental Sciences, Amity University, Noida, India
| | - Abhishek Chauhan
- Amity Institute of Environment Toxicology and Safety Management, Amity University, Noida, India
| | - Anuj Ranjan
- Amity Institute of Environment Toxicology and Safety Management, Amity University, Noida, India
- Academy of Biology and Biotechnology, Southern Federal University, Rostov-on-Don, Russia
| | - Priyanka Gopi
- Amity Institute of Forensic Sciences, Amity University, Noida, India
| | - Arabinda Ghosh
- Department of Botany, Microbiology Division, Guwahati University, Guwahati, India
| | - Hardeep Singh Tuli
- Department of Biotechnology, Maharishi Markandeshwar (Deemed to be University), Ambala, India
| | - Shafiul Haque
- Research and Scientific Studies Unit, College of Nursing and Allied Health Sciences, Jazan University, Jazan, Saudi Arabia
- Gilbert and Rose-Marie Chagoury School of Medicine, Lebanese American University, Beirut, Lebanon
- Centre of Medical and Bio-Allied Health Sciences Research, Ajman University, Ajman, United Arab Emirates
| | - Prateek Pandya
- Amity Institute of Forensic Sciences, Amity University, Noida, India
| | - Rup Lal
- Department of Zoology, University of Delhi, Delhi, India
| | - Tanu Jindal
- Amity Institute of Environmental Sciences, Amity University, Noida, India
- Amity Institute of Environment Toxicology and Safety Management, Amity University, Noida, India
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5
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Wang H, Ishchenko A, Skudlarek J, Shen P, Dzhekieva L, Painter RE, Chen YT, Bukhtiyarova M, Leithead A, Tracy R, Babaoglu K, Bahnck-Teets C, Buevich A, Cabalu TD, Labroli M, Lange H, Lei Y, Li W, Liu J, Mann PA, Meng T, Mitchell HJ, Mulhearn J, Scapin G, Sha D, Shaw AW, Si Q, Tong L, Wu C, Wu Z, Xiao JC, Xu M, Zhang LK, McKenney D, Miller RR, Black TA, Cooke A, Balibar CJ, Klein DJ, Raheem I, Walker SS. Cerastecins inhibit membrane lipooligosaccharide transport in drug-resistant Acinetobacter baumannii. Nat Microbiol 2024; 9:1244-1255. [PMID: 38649414 DOI: 10.1038/s41564-024-01667-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2023] [Accepted: 03/06/2024] [Indexed: 04/25/2024]
Abstract
Carbapenem-resistant Acinetobacter baumannii infections have limited treatment options. Synthesis, transport and placement of lipopolysaccharide or lipooligosaccharide (LOS) in the outer membrane of Gram-negative bacteria are important for bacterial virulence and survival. Here we describe the cerastecins, inhibitors of the A. baumannii transporter MsbA, an LOS flippase. These molecules are potent and bactericidal against A. baumannii, including clinical carbapenem-resistant Acinetobacter baumannii isolates. Using cryo-electron microscopy and biochemical analysis, we show that the cerastecins adopt a serpentine configuration in the central vault of the MsbA dimer, stalling the enzyme and uncoupling ATP hydrolysis from substrate flipping. A derivative with optimized potency and pharmacokinetic properties showed efficacy in murine models of bloodstream or pulmonary A. baumannii infection. While resistance development is inevitable, targeting a clinically unexploited mechanism avoids existing antibiotic resistance mechanisms. Although clinical validation of LOS transport remains undetermined, the cerastecins may open a path to narrow-spectrum treatment modalities for important nosocomial infections.
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Affiliation(s)
- Hao Wang
- Merck & Co., Inc., West Point, PA, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - Ying Lei
- Merck & Co., Inc., West Point, PA, USA
| | - Wei Li
- Merck & Co., Inc., West Point, PA, USA
| | - Jian Liu
- Merck & Co., Inc., West Point, PA, USA
| | | | - Tao Meng
- Merck & Co., Inc., Rahway, NJ, USA
| | | | | | | | - Deyou Sha
- Merck & Co., Inc., West Point, PA, USA
| | | | - Qian Si
- Merck & Co., Inc., West Point, PA, USA
| | - Ling Tong
- Merck & Co., Inc., West Point, PA, USA
| | | | - Zhe Wu
- Merck & Co., Inc., West Point, PA, USA
| | | | - Min Xu
- Merck & Co., Inc., West Point, PA, USA
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6
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Hummels KR. mSphere of Influence: Celebrating exceptions to the rule of lipid A essentiality. mSphere 2024; 9:e0063323. [PMID: 38421175 PMCID: PMC10964400 DOI: 10.1128/msphere.00633-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2024] Open
Abstract
Kate Hummels works in the field of bacterial cell envelope biosynthesis and studies the regulation of the metabolic pathways needed to build the Gram-negative cell envelope. In this mSphere of Influence article, she reflects on how the papers "A penicillin-binding protein inhibits selection of colistin-resistant, lipopoligosaccharide-deficient Acinetobacter baumannii" by Boll et al. and "Caulobacter lipid A is conditionally dispensable in the absence of fur and in the presence of anionic sphingolipids" by Zik et al. made an impact on her by studying organisms that deviate from accepted norms to highlight the plethora of unanswered questions in cell envelope biology.
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7
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Bhavya JN, Anugna SS, Premanath R. Sub-inhibitory concentrations of colistin and imipenem impact the expression of biofilm-associated genes in Acinetobacter baumannii. Arch Microbiol 2024; 206:169. [PMID: 38489041 DOI: 10.1007/s00203-024-03869-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 01/23/2024] [Accepted: 01/24/2024] [Indexed: 03/17/2024]
Abstract
Acinetobacter baumannii is an opportunistic pathogen that is responsible for nosocomial infections. Imipenem and colistin are drugs that are commonly used to treat severe infections caused by A. baumannii, such as sepsis, ventilator-associated pneumonia, and bacteremia. However, some strains of A. baumannii have become resistant to these drugs, which is a concern for public health. Biofilms produced by A. baumannii increase their resistance to antibiotics and the cells within the inner layers of biofilm are exposed to sub-inhibitory concentrations (sub-MICs) of antibiotics. There is limited information available regarding how the genes of A. baumannii are linked to biofilm formation when the bacteria are exposed to sub-MICs of imipenem and colistin. Thus, this study's objective was to explore this relationship by examining the genes involved in biofilm formation in A. baumannii when exposed to low levels of imipenem and colistin. The study found that exposing an isolate of A. baumannii to low levels of these drugs caused changes in their drug susceptibility pattern. The relative gene expression profiles of the biofilm-associated genes exhibited a change in their expression profile during short-term and long-term exposure. This study highlights the potential consequences of overuse and misuse of antibiotics, which can help bacteria become resistant to these drugs.
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Affiliation(s)
- J N Bhavya
- Nitte (Deemed to be University), Nitte University Centre for Science Education and Research, Paneer Campus, Deralakatte, Mangaluru, Karnataka, 575018, India
| | - Sureddi Sai Anugna
- Nitte (Deemed to be University), Nitte University Centre for Science Education and Research, Paneer Campus, Deralakatte, Mangaluru, Karnataka, 575018, India
| | - Ramya Premanath
- Nitte (Deemed to be University), Nitte University Centre for Science Education and Research, Paneer Campus, Deralakatte, Mangaluru, Karnataka, 575018, India.
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8
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Noel HR, Keerthi S, Ren X, Winkelman JD, Troutman JM, Palmer LD. Genetic synergy between Acinetobacter baumannii undecaprenyl phosphate biosynthesis and the Mla system impacts cell envelope and antimicrobial resistance. mBio 2024; 15:e0280423. [PMID: 38364179 PMCID: PMC10936186 DOI: 10.1128/mbio.02804-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 01/17/2024] [Indexed: 02/18/2024] Open
Abstract
Acinetobacter baumannii is a Gram-negative bacterial pathogen that poses a major health concern due to increasing multidrug resistance. The Gram-negative cell envelope is a key barrier to antimicrobial entry and includes an inner and outer membrane. The maintenance of lipid asymmetry (Mla) system is the main homeostatic mechanism by which Gram-negative bacteria maintain outer membrane asymmetry. Loss of the Mla system in A. baumannii results in attenuated virulence and increased susceptibility to membrane stressors and some antibiotics. We recently reported two strain variants of the A. baumannii type strain ATCC 17978: 17978VU and 17978UN. Here, ∆mlaF mutants in the two ATCC 17978 strains display different phenotypes for membrane stress resistance, antibiotic resistance, and pathogenicity in a murine pneumonia model. Although allele differences in obgE were previously reported to synergize with ∆mlaF to affect growth and stringent response, obgE alleles do not affect membrane stress resistance. Instead, a single-nucleotide polymorphism (SNP) in the essential gene encoding undecaprenyl pyrophosphate (Und-PP) synthase, uppS, results in decreased enzymatic rate and decrease in total Und-P levels in 17978UN compared to 17978VU. The UppSUN variant synergizes with ∆mlaF to reduce capsule and lipooligosaccharide (LOS) levels, increase susceptibility to membrane stress and antibiotics, and reduce persistence in a mouse lung infection. Und-P is a lipid glycan carrier required for the biosynthesis of A. baumannii capsule, cell wall, and glycoproteins. These findings uncover synergy between Und-P and the Mla system in maintaining the A. baumannii cell envelope and antibiotic resistance.IMPORTANCEAcinetobacter baumannii is a critical threat to global public health due to its multidrug resistance and persistence in hospital settings. Therefore, novel therapeutic approaches are urgently needed. We report that a defective undecaprenyl pyrophosphate synthase (UppS) paired with a perturbed Mla system leads to synthetically sick cells that are more susceptible to clinically relevant antibiotics and show reduced virulence in a lung infection model. These results suggest that targeting UppS or undecaprenyl species and the Mla system may resensitize A. baumannii to antibiotics in combination therapies. This work uncovers a previously unknown synergistic relationship in cellular envelope homeostasis that could be leveraged for use in combination therapy against A. baumannii.
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Affiliation(s)
- Hannah R. Noel
- Department of Microbiology and Immunology, University of Illinois Chicago, Chicago, Illinois, USA
| | - Sowmya Keerthi
- Department of Chemistry, University of North Carolina Charlotte, Charlotte, North Carolina, USA
| | - Xiaomei Ren
- Department of Microbiology and Immunology, University of Illinois Chicago, Chicago, Illinois, USA
| | | | - Jerry M. Troutman
- Department of Chemistry, University of North Carolina Charlotte, Charlotte, North Carolina, USA
| | - Lauren D. Palmer
- Department of Microbiology and Immunology, University of Illinois Chicago, Chicago, Illinois, USA
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9
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VanOtterloo LM, Macias LA, Powers MJ, Brodbelt JS, Trent MS. Characterization of Acinetobacter baumannii core oligosaccharide synthesis reveals novel aspects of lipooligosaccharide assembly. mBio 2024; 15:e0301323. [PMID: 38349180 PMCID: PMC10936431 DOI: 10.1128/mbio.03013-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 01/12/2024] [Indexed: 03/14/2024] Open
Abstract
A fundamental feature of Gram-negative bacteria is their outer membrane that protects the cell against environmental stressors. This defense is predominantly due to its asymmetry, with glycerophospholipids located in the inner leaflet and lipopolysaccharide (LPS) or lipooligosaccharide (LOS) confined to the outer leaflet. LPS consists of a lipid A anchor, a core oligosaccharide, and a distal O-antigen while LOS lacks O-antigen. While LPS/LOS is typically essential for growth, this is not the case for Acinetobacter baumannii. Despite this unique property, the synthesis of the core oligosaccharide of A. baumannii LOS is not well-described. Here, we characterized the LOS chemotypes of A. baumannii strains with mutations in a predicted core oligosaccharide locus via tandem mass spectrometry. This allowed for an extensive identification of genes required for core assembly that can be exploited to generate precise structural LOS modifications in many A. baumannii strains. We further investigated two chemotypically identical yet phenotypically distinct mutants, ∆2903 and ∆lpsB, that exposed a possible link between LOS and the peptidoglycan cell wall-two cell envelope components whose coordination has not yet been described in A. baumannii. Selective reconstruction of the core oligosaccharide via expression of 2903 and LpsB revealed that these proteins rely on each other for the unusual tandem transfer of two residues, KdoIII and N-acetylglucosaminuronic acid. The data presented not only allow for better usage of A. baumannii as a tool to study outer membrane integrity but also provide further evidence for a novel mechanism of core oligosaccharide assembly. IMPORTANCE Acinetobacter baumannii is a multidrug-resistant pathogen that produces lipooligosaccharide (LOS), a glycolipid that confers protective asymmetry to the bacterial outer membrane. The core oligosaccharide is a ubiquitous component of LOS that typically follows a well-established model of synthesis. In addition to providing an extensive analysis of the genes involved in the synthesis of the core region, we demonstrate that this organism has evidently diverged from the long-held archetype of core synthesis. Moreover, our data suggest that A. baumannii LOS assembly is important for cell division and likely intersects with the synthesis of the peptidoglycan cell wall, another essential component of the Gram-negative cell envelope. This connection between LOS and cell wall synthesis provides an intriguing foundation for a unique method of outer membrane biogenesis and cell envelope coordination.
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Affiliation(s)
- Leah M. VanOtterloo
- Department of Microbiology, College of Art and Sciences, University of Georgia, Athens, Georgia, USA
| | - Luis A. Macias
- Department of Chemistry, University of Texas at Austin, Austin, Texas, USA
| | - Matthew J. Powers
- Department of Microbiology, College of Art and Sciences, University of Georgia, Athens, Georgia, USA
| | | | - M. Stephen Trent
- Department of Microbiology, College of Art and Sciences, University of Georgia, Athens, Georgia, USA
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
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10
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Ward RD, Tran JS, Banta AB, Bacon EE, Rose WE, Peters JM. Essential gene knockdowns reveal genetic vulnerabilities and antibiotic sensitivities in Acinetobacter baumannii. mBio 2024; 15:e0205123. [PMID: 38126769 PMCID: PMC10865783 DOI: 10.1128/mbio.02051-23] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Accepted: 11/20/2023] [Indexed: 12/23/2023] Open
Abstract
The emergence of multidrug-resistant Gram-negative bacteria underscores the need to define genetic vulnerabilities that can be therapeutically exploited. The Gram-negative pathogen, Acinetobacter baumannii, is considered an urgent threat due to its propensity to evade antibiotic treatments. Essential cellular processes are the target of existing antibiotics and a likely source of new vulnerabilities. Although A. baumannii essential genes have been identified by transposon sequencing, they have not been prioritized by sensitivity to knockdown or antibiotics. Here, we take a systems biology approach to comprehensively characterize A. baumannii essential genes using CRISPR interference (CRISPRi). We show that certain essential genes and pathways are acutely sensitive to knockdown, providing a set of vulnerable targets for future therapeutic investigation. Screening our CRISPRi library against last-resort antibiotics uncovered genes and pathways that modulate beta-lactam sensitivity, an unexpected link between NADH dehydrogenase activity and growth inhibition by polymyxins, and anticorrelated phenotypes that may explain synergy between polymyxins and rifamycins. Our study demonstrates the power of systematic genetic approaches to identify vulnerabilities in Gram-negative pathogens and uncovers antibiotic-essential gene interactions that better inform combination therapies.IMPORTANCEAcinetobacter baumannii is a hospital-acquired pathogen that is resistant to many common antibiotic treatments. To combat resistant A. baumannii infections, we need to identify promising therapeutic targets and effective antibiotic combinations. In this study, we comprehensively characterize the genes and pathways that are critical for A. baumannii viability. We show that genes involved in aerobic metabolism are central to A. baumannii physiology and may represent appealing drug targets. We also find antibiotic-gene interactions that may impact the efficacy of carbapenems, rifamycins, and polymyxins, providing a new window into how these antibiotics function in mono- and combination therapies. Our studies offer a useful approach for characterizing interactions between drugs and essential genes in pathogens to inform future therapies.
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Affiliation(s)
- Ryan D. Ward
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Jennifer S. Tran
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Amy B. Banta
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Emily E. Bacon
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Warren E. Rose
- Pharmacy Practice Division, School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Jason M. Peters
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Center for Genomic Science Innovation, University of Wisconsin-Madison, Madison, Wisconsin, USA
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11
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Hamami E, Huo W, Neal K, Neisewander I, Geisinger E, Isberg RR. Identification of essential genes that support fitness of Acinetobacter baumannii efflux pump overproducers in the presence of fluoroquinolone. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.04.574119. [PMID: 38260615 PMCID: PMC10802289 DOI: 10.1101/2024.01.04.574119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Acinetobacter baumannii is a nosocomial pathogen often associated with multidrug resistance (MDR) infections. Fluoroquinolone resistance (FQR) due to drug target site mutations and elevated expression of RND drug transporters is common among clinical isolates. We describe here a CRISPRi platform that identifies hypomorphic mutations that preferentially altered drug sensitivity in RND pump overproducers. An sgRNA library against essential genes of A. baumannii was constructed with single and double nucleotide mutations that produced titratable knockdown efficiencies and introduced into multiple strain backgrounds. Other than nusG depletions, there were few candidates in the absence of drug treatment that showed lowered fitness specifically in strains overexpressing clinically relevant RND efflux pumps AdeAB, AdeIJK, or AdeFGH. In the presence of ciprofloxacin, the hypomorphs causing hypersensitivity were predicted to result in outer membrane dysfunction, to which the AdeFGH overproducer appeared particularly sensitive. Depletions of either the outer membrane assembly BAM complex, LOS biogenesis proteins, or Lpt proteins involved in LOS transport to the outer membrane caused drug hypersensitivity in at least two of the three pump overproducers. On the other hand, depletions of translation-associated proteins, as well as components of the proton-pumping ATP synthase pump resulted in fitness benefits for at least two pump-overproducing strains in the presence of the drug. Therefore, pump overproduction exacerbated stress caused by defective outer membrane integrity, while the efficacy of drug resistance in efflux overproducers was enhanced by slowed translation or defects in ATP synthesis linked to the control of proton movement across the bacterial membrane.
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Affiliation(s)
- Efrat Hamami
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
| | - Wenwen Huo
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
| | - Katherine Neal
- Department of Biochemistry, Curry College, Milton, MA, USA
| | - Isabelle Neisewander
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
| | - Edward Geisinger
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
- Department of Biology, Northeastern University, Boston, MA, 02115, USA
| | - Ralph R Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
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12
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Bjånes E, Koh T, Qayum T, Zurich R, McCabe S, Hampel K, Cartwright L, Nizet V. Exploring Roles of the Polysaccharide Capsule in Pathogenesis of Hypervirulent Acinetobacter baumannii Clinical Isolate Lac-4. Antibiotics (Basel) 2023; 13:10. [PMID: 38275320 PMCID: PMC10812722 DOI: 10.3390/antibiotics13010010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 12/15/2023] [Accepted: 12/18/2023] [Indexed: 01/27/2024] Open
Abstract
The frequently multidrug-resistant bacterial pathogen Acinetobacter baumannii is a leading cause of nosocomial infections, including ventilator-associated pneumonia, such that the World Health Organization and US Centers for Disease Control and Prevention have declared it a top priority candidate for novel drug development. Nearly all clinical A. baumannii strains express a thick surface polysaccharide capsule that protects against desiccation, host defenses, and disinfectants. In this study, we investigated the contribution of the polysaccharide capsule to virulence caused by the A. baumannii clinical isolate Ab Lac-4, which is rare in its ability to cause pneumonia and disseminated sepsis in healthy mice. We assessed the role of the capsule in wildtype Lac-4 (WT) by generating a premature stop codon in wza, which codes for the polysaccharide export protein. The wza# mutant was hypersensitive to killing by complement, whole blood, and healthy human neutrophils compared to WT and a revertant mutant (wza-Rev). Furthermore, the wza# mutant was highly attenuated in murine sepsis and unable to disseminate from the lungs during pneumonia. This study reinforces the capsule as a key contributor to Ab Lac-4 hypervirulence.
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Affiliation(s)
- Elisabet Bjånes
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Truman Koh
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Tariq Qayum
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Raymond Zurich
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Sinead McCabe
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Kegan Hampel
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Lisa Cartwright
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Victor Nizet
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093, USA
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13
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Shahzad S, Willcox MDP, Rayamajhee B. A Review of Resistance to Polymyxins and Evolving Mobile Colistin Resistance Gene ( mcr) among Pathogens of Clinical Significance. Antibiotics (Basel) 2023; 12:1597. [PMID: 37998799 PMCID: PMC10668746 DOI: 10.3390/antibiotics12111597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 10/26/2023] [Accepted: 11/04/2023] [Indexed: 11/25/2023] Open
Abstract
The global rise in antibiotic resistance in bacteria poses a major challenge in treating infectious diseases. Polymyxins (e.g., polymyxin B and colistin) are last-resort antibiotics against resistant Gram-negative bacteria, but the effectiveness of polymyxins is decreasing due to widespread resistance among clinical isolates. The aim of this literature review was to decipher the evolving mechanisms of resistance to polymyxins among pathogens of clinical significance. We deciphered the molecular determinants of polymyxin resistance, including distinct intrinsic molecular pathways of resistance as well as evolutionary characteristics of mobile colistin resistance. Among clinical isolates, Acinetobacter stains represent a diversified evolution of resistance, with distinct molecular mechanisms of intrinsic resistance including naxD, lpxACD, and stkR gene deletion. On the other hand, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa are usually resistant via the PhoP-PhoQ and PmrA-PmrB pathways. Molecular evolutionary analysis of mcr genes was undertaken to show relative relatedness across the ten main lineages. Understanding the molecular determinants of resistance to polymyxins may help develop suitable and effective methods for detecting polymyxin resistance determinants and the development of novel antimicrobial molecules.
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Affiliation(s)
- Shakeel Shahzad
- School of Optometry and Vision Science, University of New South Wales, Sydney, NSW 2052, Australia;
| | - Mark D. P. Willcox
- School of Optometry and Vision Science, University of New South Wales, Sydney, NSW 2052, Australia;
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14
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Mikheyeva IV, Sun J, Huang KC, Silhavy TJ. Mechanism of outer membrane destabilization by global reduction of protein content. Nat Commun 2023; 14:5715. [PMID: 37714857 PMCID: PMC10504340 DOI: 10.1038/s41467-023-40396-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Accepted: 07/26/2023] [Indexed: 09/17/2023] Open
Abstract
The outer membrane (OM) of Gram-negative bacteria such as Escherichia coli is an asymmetric bilayer with the glycolipid lipopolysaccharide (LPS) in the outer leaflet and glycerophospholipids in the inner. Nearly all integral OM proteins (OMPs) have a characteristic β-barrel fold and are assembled in the OM by the BAM complex, which contains one essential β-barrel protein (BamA), one essential lipoprotein (BamD), and three non-essential lipoproteins (BamBCE). A gain-of-function mutation in bamA enables survival in the absence of BamD, showing that the essential function of this protein is regulatory. Here, we demonstrate that the global reduction in OMPs caused by BamD loss weakens the OM, altering cell shape and causing OM rupture in spent medium. To fill the void created by OMP loss, phospholipids (PLs) flip into the outer leaflet. Under these conditions, mechanisms that remove PLs from the outer leaflet create tension between the OM leaflets, which contributes to membrane rupture. Rupture is prevented by suppressor mutations that release the tension by halting PL removal from the outer leaflet. However, these suppressors do not restore OM stiffness or normal cell shape, revealing a possible connection between OM stiffness and cell shape.
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Affiliation(s)
- Irina V Mikheyeva
- Department of Molecular Biology, Princeton University, Princeton, NJ, 08540, USA
| | - Jiawei Sun
- Department of Bioengineering, Stanford University, Stanford, CA, 94305, USA
| | - Kerwyn Casey Huang
- Department of Bioengineering, Stanford University, Stanford, CA, 94305, USA.
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, 94305, USA.
- Chan Zuckerberg Biohub, San Francisco, CA, 94158, USA.
| | - Thomas J Silhavy
- Department of Molecular Biology, Princeton University, Princeton, NJ, 08540, USA.
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15
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Gadar K, de Dios R, Kadeřábková N, Prescott TAK, Mavridou DAI, McCarthy RR. Disrupting iron homeostasis can potentiate colistin activity and overcome colistin resistance mechanisms in Gram-Negative Bacteria. Commun Biol 2023; 6:937. [PMID: 37704838 PMCID: PMC10499790 DOI: 10.1038/s42003-023-05302-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 08/29/2023] [Indexed: 09/15/2023] Open
Abstract
Acinetobacter baumannii is a Gram-negative priority pathogen that can readily overcome antibiotic treatment through a range of intrinsic and acquired resistance mechanisms. Treatment of carbapenem-resistant A. baumannii largely relies on the use of colistin in cases where other treatment options have been exhausted. However, the emergence of resistance against this last-line drug has significantly increased amongst clinical strains. In this study, we identify the phytochemical kaempferol as a potentiator of colistin activity. When administered singularly, kaempferol has no effect on growth but does impact biofilm formation. Nonetheless, co-administration of kaempferol with sub-inhibitory concentrations of colistin exposes bacteria to a metabolic Achilles heel, whereby kaempferol-induced dysregulation of iron homeostasis leads to bacterial killing. We demonstrate that this effect is due to the disruption of Fenton's reaction, and therefore to a lethal build-up of toxic reactive oxygen species in the cell. Furthermore, we show that this vulnerability can be exploited to overcome both intrinsic and acquired colistin resistance in clinical strains of A. baumannii and E. coli in vitro and in the Galleria mellonella model of infection. Overall, our findings provide a proof-of-principle demonstration that targeting iron homeostasis is a promising strategy for enhancing the efficacy of colistin and overcoming colistin-resistant infections.
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Affiliation(s)
- Kavita Gadar
- Biosciences, Department of Life Sciences, College of Health, Medicine and Life Sciences, Brunel University London, Uxbridge, UB8 3PH, UK
| | - Rubén de Dios
- Biosciences, Department of Life Sciences, College of Health, Medicine and Life Sciences, Brunel University London, Uxbridge, UB8 3PH, UK
| | - Nikol Kadeřábková
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX, 78712, USA
| | | | - Despoina A I Mavridou
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX, 78712, USA
- John Ring LaMontagne Centre for Infectious Diseases, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Ronan R McCarthy
- Biosciences, Department of Life Sciences, College of Health, Medicine and Life Sciences, Brunel University London, Uxbridge, UB8 3PH, UK.
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16
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Ward RD, Tran JS, Banta AB, Bacon EE, Rose WE, Peters JM. Essential Gene Knockdowns Reveal Genetic Vulnerabilities and Antibiotic Sensitivities in Acinetobacter baumannii. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.02.551708. [PMID: 37577569 PMCID: PMC10418195 DOI: 10.1101/2023.08.02.551708] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
The emergence of multidrug-resistant Gram-negative bacteria underscores the need to define genetic vulnerabilities that can be therapeutically exploited. The Gram-negative pathogen, Acinetobacter baumannii, is considered an urgent threat due to its propensity to evade antibiotic treatments. Essential cellular processes are the target of existing antibiotics and a likely source of new vulnerabilities. Although A. baumannii essential genes have been identified by transposon sequencing (Tn-seq), they have not been prioritized by sensitivity to knockdown or antibiotics. Here, we take a systems biology approach to comprehensively characterize A. baumannii essential genes using CRISPR interference (CRISPRi). We show that certain essential genes and pathways are acutely sensitive to knockdown, providing a set of vulnerable targets for future therapeutic investigation. Screening our CRISPRi library against last-resort antibiotics uncovered genes and pathways that modulate beta-lactam sensitivity, an unexpected link between NADH dehydrogenase activity and growth inhibition by polymyxins, and anticorrelated phenotypes that underpin synergy between polymyxins and rifamycins. Our study demonstrates the power of systematic genetic approaches to identify vulnerabilities in Gram-negative pathogens and uncovers antibiotic-essential gene interactions that better inform combination therapies.
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Affiliation(s)
- Ryan D Ward
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, WI 53705
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, WI 53706
| | - Jennifer S Tran
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, WI 53705
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI 53706
| | - Amy B Banta
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, WI 53705
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI 53726
| | - Emily E Bacon
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, WI 53705
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, WI 53706
| | - Warren E Rose
- Pharmacy Practice Division, School of Pharmacy, University of Wisconsin-Madison, Madison, WI 53705
| | - Jason M Peters
- Pharmaceutical Sciences Division, School of Pharmacy, University of Wisconsin-Madison, Madison, WI 53705
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, WI 53726
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706
- Center for Genomic Science Innovation, University of Wisconsin-Madison, Madison, WI 53706
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17
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Dhakephalkar T, Stukey G, Guan Z, Carman GM, Klein EA. Characterization of an evolutionarily distinct bacterial ceramide kinase from Caulobacter crescentus. J Biol Chem 2023:104894. [PMID: 37286040 PMCID: PMC10331486 DOI: 10.1016/j.jbc.2023.104894] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 05/27/2023] [Accepted: 06/01/2023] [Indexed: 06/09/2023] Open
Abstract
A common feature among nearly all Gram-negative bacteria is the requirement for lipopolysaccharide (LPS) in the outer leaflet of the outer membrane. LPS provides structural integrity to the bacterial membrane which aids bacteria in maintaining their shape and acts as a barrier from environmental stress and harmful substances such as detergents and antibiotics. Recent work has demonstrated that Caulobacter crescentus can survive without LPS due to the presence of the anionic sphingolipid ceramide-phosphoglycerate. Based on genetic evidence, we predicted that protein CpgB functions as a ceramide kinase and performs the first step in generating the phosphoglycerate head group. Here, we characterized the kinase activity of recombinantly expressed CpgB and demonstrated that it can phosphorylate ceramide to form ceramide 1-phosphate. The pH optimum for CpgB was 7.5, and the enzyme required Mg2+ as a cofactor. Mn2+, but not other divalent cations, could substitute for Mg2+. Under these conditions, the enzyme exhibited typical Michaelis-Menten kinetics with respect to NBD-C6-ceramide (Km,app=19.2 ± 5.5 μM; Vmax,app=2590 ± 230 pmol/min/mg enzyme) and ATP (Km,app=0.29 ± 0.07 mM; Vmax,app=10100 ± 996 pmol/min/mg enzyme). Phylogenetic analysis of CpgB revealed that CpgB belongs to a new class of ceramide kinases which is distinct from its eukaryotic counterpart; furthermore, the pharmacological inhibitor of human ceramide kinase (NVP-231) had no effect on CpgB. The characterization of a new bacterial ceramide kinase opens avenues for understanding the structure and function of the various microbial phosphorylated sphingolipids.
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Affiliation(s)
| | - Geordan Stukey
- Department of Food Science, Rutgers University, New Brunswick, NJ 08901, USA; Rutgers Center for Lipid Research, New Jersey Institute for Food Nutrition and Health, Rutgers University, New Brunswick, NJ 08901, USA
| | - Ziqiang Guan
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
| | - George M Carman
- Department of Food Science, Rutgers University, New Brunswick, NJ 08901, USA; Rutgers Center for Lipid Research, New Jersey Institute for Food Nutrition and Health, Rutgers University, New Brunswick, NJ 08901, USA
| | - Eric A Klein
- Biology Department, Rutgers University-Camden, Camden, NJ 08102, USA; Department of Food Science, Rutgers University, New Brunswick, NJ 08901, USA; Rutgers Center for Lipid Research, New Jersey Institute for Food Nutrition and Health, Rutgers University, New Brunswick, NJ 08901, USA; Center for Computational and Integrative Biology, Rutgers University-Camden, Camden, NJ 08102, USA.
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18
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Oi KK, Moehle K, Schuster M, Zerbe O. Early Molecular Insights into Thanatin Analogues Binding to A. baumannii LptA. Molecules 2023; 28:4335. [PMID: 37298811 PMCID: PMC10254193 DOI: 10.3390/molecules28114335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 05/11/2023] [Accepted: 05/12/2023] [Indexed: 06/12/2023] Open
Abstract
The cationic antimicrobial ß-hairpin, thanatin, was recently developed into drug-like analogues active against carbapenem-resistant Enterobacteriaceae (CRE). The analogues represent new antibiotics with a novel mode of action targeting LptA in the periplasm and disrupting LPS transport. The compounds lose antimicrobial efficacy when the sequence identity to E. coli LptA falls below 70%. We wanted to test the thanatin analogues against LptA of a phylogenetic distant organism and investigate the molecular determinants of inactivity. Acinetobacter baumannii (A. baumannii) is a critical Gram-negative pathogen that has gained increasing attention for its multi-drug resistance and hospital burden. A. baumannii LptA shares 28% sequence identity with E. coli LptA and displays an intrinsic resistance to thanatin and thanatin analogues (MIC values > 32 µg/mL) through a mechanism not yet described. We investigated the inactivity further and discovered that these CRE-optimized derivatives can bind to LptA of A. baumannii in vitro, despite the high MIC values. Herein, we present a high-resolution structure of A. baumannii LptAm in complex with a thanatin derivative 7 and binding affinities of selected thanatin derivatives. Together, these data offer structural insights into why thanatin derivatives are inactive against A. baumannii LptA, despite binding events in vitro.
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Affiliation(s)
| | | | | | - Oliver Zerbe
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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19
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Dhakephalkar T, Stukey G, Guan Z, Carman GM, Klein EA. Characterization of an evolutionarily distinct bacterial ceramide kinase from Caulobacter crescentus. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.01.538943. [PMID: 37205603 PMCID: PMC10187206 DOI: 10.1101/2023.05.01.538943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
A common feature among nearly all Gram-negative bacteria is the requirement for lipopolysaccharide (LPS) in the outer leaflet of the outer membrane. LPS provides structural integrity to the bacterial membrane which aids bacteria in maintaining their shape and acts as a barrier from environmental stress and harmful substances such as detergents and antibiotics. Recent work has demonstrated that Caulobacter crescentus can survive without LPS due to the presence of the anionic sphingolipid ceramide-phosphoglycerate. Based on genetic evidence, we predicted that protein CpgB functions as a ceramide kinase and performs the first step in generating the phosphoglycerate head group. Here, we characterized the kinase activity of recombinantly expressed CpgB and demonstrated that it can phosphorylate ceramide to form ceramide 1-phosphate. The pH optimum for CpgB was 7.5, and the enzyme required Mg 2+ as a cofactor. Mn 2+ , but not other divalent cations, could substitute for Mg 2+ . Under these conditions, the enzyme exhibited typical Michaelis-Menten kinetics with respect to NBD-C6-ceramide (K m,app =19.2 ± 5.5 μM; V max,app =2586.29 ± 231.99 pmol/min/mg enzyme) and ATP (K m,app =0.29 ± 0.07 mM; V max,app =10067.57 ± 996.85 pmol/min/mg enzyme). Phylogenetic analysis of CpgB revealed that CpgB belongs to a new class of ceramide kinases which is distinct from its eukaryotic counterpart; furthermore, the pharmacological inhibitor of human ceramide kinase (NVP-231) had no effect on CpgB. The characterization of a new bacterial ceramide kinase opens avenues for understanding the structure and function of the various microbial phosphorylated sphingolipids.
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20
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Mikheyeva IV, Sun J, Huang KC, Silhavy TJ. Mechanism of outer membrane destabilization by global reduction of protein content. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.19.529137. [PMID: 36865163 PMCID: PMC9980000 DOI: 10.1101/2023.02.19.529137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
The outer membrane (OM) of Gram-negative bacteria such as Escherichia coli is an asymmetric bilayer with the glycolipid lipopolysaccharide (LPS) in the outer leaflet and glycerophospholipids in the inner. Nearly all integral OM proteins (OMPs) have a characteristic β-barrel fold and are assembled in the OM by the BAM complex, which contains one essential β-barrel protein (BamA), one essential lipoprotein (BamD), and three non-essential lipoproteins (BamBCE). A gain-of-function mutation in bamA enables survival in the absence of BamD, showing that the essential function of this protein is regulatory. We demonstrate that the global reduction in OMPs caused by BamD loss weakens the OM, altering cell shape and causing OM rupture in spent medium. To fill the void created by OMP loss, PLs flip into the outer leaflet. Under these conditions, mechanisms that remove PLs from the outer leaflet create tension between the OM leaflets, which contributes to membrane rupture. Rupture is prevented by suppressor mutations that release the tension by halting PL removal from the outer leaflet. However, these suppressors do not restore OM stiffness or normal cell shape, revealing a possible connection between OM stiffness and cell shape. Significance Statement The outer membrane (OM) is a selective permeability barrier that contributes to the intrinsic antibiotic resistance of Gram-negative bacteria. Biophysical characterization of the roles of the component proteins, lipopolysaccharides, and phospholipids is limited by both the essentiality of the OM and its asymmetrical organization. In this study, we dramatically change OM physiology by limiting the protein content, which requires phospholipid localization to the outer leaflet and thus disrupts OM asymmetry. By characterizing the perturbed OM of various mutants, we provide novel insight into the links among OM composition, OM stiffness, and cell shape regulation. These findings deepen our understanding of bacterial cell envelope biology and provide a platform for further interrogation of OM properties.
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Affiliation(s)
- Irina V. Mikheyeva
- Department of Molecular Biology, Princeton University, Princeton, NJ 08540, USA
| | - Jiawei Sun
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Kerwyn Casey Huang
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA
- Chan Zuckerberg Biohub, San Francisco, CA 94158, USA
| | - Thomas J. Silhavy
- Department of Molecular Biology, Princeton University, Princeton, NJ 08540, USA
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21
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Sperandeo P, Martorana AM, Zaccaria M, Polissi A. Targeting the LPS export pathway for the development of novel therapeutics. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2023; 1870:119406. [PMID: 36473551 DOI: 10.1016/j.bbamcr.2022.119406] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 10/14/2022] [Accepted: 11/01/2022] [Indexed: 12/12/2022]
Abstract
The rapid rise of multi-resistant bacteria is a global health threat. This is especially serious for Gram-negative bacteria in which the impermeable outer membrane (OM) acts as a shield against antibiotics. The development of new drugs with novel modes of actions to combat multi-drug resistant pathogens requires the selection of suitable processes to be targeted. The LPS export pathway is an excellent under exploited target for drug development. Indeed, LPS is the major determinant of the OM permeability barrier, and its biogenetic pathway is conserved in most Gram-negatives. Here we describe efforts to identify inhibitors of the multiprotein Lpt system that transports LPS to the cell surface. Despite none of these molecules has been approved for clinical use, they may represent valuable compounds for optimization. Finally, the recent discovery of a link between inhibition of LPS biogenesis and changes in peptidoglycan structure uncovers additional targets to develop novel therapeutic strategies.
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Affiliation(s)
- Paola Sperandeo
- Department of Pharmacological and Biomolecular Sciences, Via Balzaretti 9, 20133 Milano, Italy
| | - Alessandra M Martorana
- Department of Pharmacological and Biomolecular Sciences, Via Balzaretti 9, 20133 Milano, Italy
| | - Marta Zaccaria
- Department of Pharmacological and Biomolecular Sciences, Via Balzaretti 9, 20133 Milano, Italy
| | - Alessandra Polissi
- Department of Pharmacological and Biomolecular Sciences, Via Balzaretti 9, 20133 Milano, Italy.
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22
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Bjanes E, Zhou J, Qayum T, Krishnan N, Zurich RH, Menon ND, Hoffman A, Fang RH, Zhang L, Nizet V. Outer Membrane Vesicle-Coated Nanoparticle Vaccine Protects Against Acinetobacter baumannii Pneumonia and Sepsis. ADVANCED NANOBIOMED RESEARCH 2023; 3:2200130. [PMID: 37151210 PMCID: PMC10156090 DOI: 10.1002/anbr.202200130] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The highly multidrug-resistant (MDR) Gram-negative bacterial pathogen Acinetobacter baumannii is a top global health priority where an effective vaccine could protect susceptible populations and limit resistance acquisition. Outer membrane vesicles (OMVs) shed from Gram-negative bacteria are enriched with virulence factors and membrane lipids but heterogeneous in size and cargo. We report a vaccine platform combining precise and replicable nanoparticle technology with immunogenic A. baumannii OMVs (Ab-OMVs). Gold nanoparticle cores coated with Ab-OMVs (Ab-NPs) induced robust IgG titers in rabbits that enhanced human neutrophil opsonophagocytic killing and passively protected against lethal A. baumannii sepsis in mice. Active Ab-NP immunization in mice protected against sepsis and pneumonia, accompanied by B cell recruitment to draining lymph nodes, activation of dendritic cell markers, improved splenic neutrophil responses, and mitigation of proinflammatory cytokine storm. Nanoparticles are an efficient and efficacious platform for OMV vaccine delivery against A. baumannii and perhaps other high-priority MDR pathogens.
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Affiliation(s)
- Elisabet Bjanes
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, California 92093, USA
| | - Jiarong Zhou
- Department of Nanoengineering, University of California San Diego, La Jolla, California 92093, USA
| | - Tariq Qayum
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, California 92093, USA
| | - Nishta Krishnan
- Department of Nanoengineering, University of California San Diego, La Jolla, California 92093, USA
| | - Raymond H. Zurich
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, California 92093, USA
| | - Nitasha D. Menon
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, California 92093, USA
- School of Biotechnology, Amrita Vishwa Vidyapeetham, Amritapuri, Kerala, India
| | - Alexandria Hoffman
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, California 92093, USA
| | - Ronnie H. Fang
- Department of Nanoengineering, University of California San Diego, La Jolla, California 92093, USA
| | - Liangfang Zhang
- Department of Nanoengineering, University of California San Diego, La Jolla, California 92093, USA
| | - Victor Nizet
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, California 92093, USA
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, California 92093, USA
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23
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Yang Z, Song M, Li X, Zhang Q, Shen J, Zhu K. Synergy of outer membrane disruptor SLAP-S25 with hydrophobic antibiotics against Gram-negative pathogens. J Antimicrob Chemother 2022; 78:263-271. [PMID: 36385317 DOI: 10.1093/jac/dkac387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 10/26/2022] [Indexed: 11/18/2022] Open
Abstract
OBJECTIVES An effective strategy for combating MDR Gram-negative pathogens can greatly reduce the cost and shorten the antibiotic development progress. Here, we investigated the synergistic activity of outer membrane disruptor SLAP-S25 in combination with hydrophobic antibiotics (LogP > 2, including novobiocin, erythromycin, clindamycin and rifampicin) against MDR Gram-negative pathogens. METHODS Five representative Gram-negative bacteria were selected as model strains to analyse the synergistic combination of SLAP-S25 and hydrophobic antibiotics. Carbapenem-resistant hypervirulent Klebsiella pneumoniae CRHvKP4 was used to investigate the synergistic mechanism. The in vivo synergistically therapeutic activity of SLAP-S25 and hydrophobic antibiotics was measured in the mouse peritonitis/sepsis model infected with K. pneumoniae CRHvKP4. RESULTS SLAP-S25 disrupted the outer membrane by removing LPS from Gram-negative bacteria, facilitating the entry of hydrophobic antibiotics to kill MDR Gram-negative pathogens. Moreover, the combination of SLAP-S25 and rifampicin exhibited promising therapeutic effects in the mouse infection model infected with K. pneumoniae CRHvKP4. CONCLUSIONS Our findings provide a potential therapeutic strategy to combine SLAP-S25 with hydrophobic antibiotics for combating MDR Gram-negative pathogens.
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Affiliation(s)
- Zhiqiang Yang
- Department of Basic Veterinary Medicine, Key Laboratory of Traditional Chinese Veterinary Medicine Biology, Ministry of Agriculture and Rural Affairs, College of VeterinaryMedicine, China Agricultural University, Beijing 100193, China
| | - Meirong Song
- Department of Basic Veterinary Medicine, Key Laboratory of Traditional Chinese Veterinary Medicine Biology, Ministry of Agriculture and Rural Affairs, College of VeterinaryMedicine, China Agricultural University, Beijing 100193, China
| | - Xiaoyu Li
- Department of Basic Veterinary Medicine, Key Laboratory of Traditional Chinese Veterinary Medicine Biology, Ministry of Agriculture and Rural Affairs, College of VeterinaryMedicine, China Agricultural University, Beijing 100193, China
| | - Qi Zhang
- Department of Basic Veterinary Medicine, Key Laboratory of Traditional Chinese Veterinary Medicine Biology, Ministry of Agriculture and Rural Affairs, College of VeterinaryMedicine, China Agricultural University, Beijing 100193, China
| | - Jianzhong Shen
- Department of Basic Veterinary Medicine, Key Laboratory of Traditional Chinese Veterinary Medicine Biology, Ministry of Agriculture and Rural Affairs, College of VeterinaryMedicine, China Agricultural University, Beijing 100193, China.,Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou 510642, China
| | - Kui Zhu
- Department of Basic Veterinary Medicine, Key Laboratory of Traditional Chinese Veterinary Medicine Biology, Ministry of Agriculture and Rural Affairs, College of VeterinaryMedicine, China Agricultural University, Beijing 100193, China.,Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou 510642, China
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PBP1A Directly Interacts with the Divisome Complex to Promote Septal Peptidoglycan Synthesis in Acinetobacter baumannii. J Bacteriol 2022; 204:e0023922. [PMID: 36317921 PMCID: PMC9765026 DOI: 10.1128/jb.00239-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
The class A penicillin-binding proteins (aPBPs), PBP1A and PBP1B, are major peptidoglycan synthases that synthesize more than half of the peptidoglycan per generation in Escherichia coli. Whereas aPBPs have distinct roles in peptidoglycan biosynthesis during growth (i.e., elongation and division), they are semiredundant; disruption of either is rescued by the other to maintain envelope homeostasis and promote proper growth. Acinetobacter baumannii is a nosocomial pathogen that has a high propensity to overcome antimicrobial treatment. A. baumannii contains both PBP1A and PBP1B (encoded by mrcA and mrcB, respectively), but only mrcA deletion decreased fitness and contributed to colistin resistance through inactivation of lipooligosaccharide biosynthesis, indicating that PBP1B was not functionally redundant with the PBP1A activity. While previous studies suggested a distinct role for PBP1A in division, it was unknown whether its role in septal peptidoglycan biosynthesis was direct. Here, we show that A. baumannii PBP1A has a direct role in division through interactions with divisome components. PBP1A localizes to septal sites during growth, where it interacts with the transpeptidase PBP3, an essential division component that regulates daughter cell formation. PBP3 overexpression was sufficient to rescue the division defect in ΔmrcA A. baumannii; however, PBP1A overexpression was not sufficient to rescue the septal defect when PBP3 was inhibited, suggesting that their activity is not redundant. Overexpression of a major dd-carboxypeptidase, PBP5, also restored the canonical A. baumannii coccobacilli morphology in ΔmrcA cells. Together, these data support a direct role for PBP1A in A. baumannii division and highlights its role as a septal peptidoglycan synthase. IMPORTANCE Peptidoglycan biosynthesis is a validated target of β-lactam antibiotics, and it is critical that we understand essential processes in multidrug-resistant pathogens such as Acinetobacter baumannii. While model systems such as Escherichia coli have shown that PBP1A is associated with side wall peptidoglycan synthesis, we show herein that A. baumannii PBP1A directly interacts with the divisome component PBP3 to promote division, suggesting a unique role for the enzyme in this highly drug-resistant nosocomial pathogen. A. baumannii demonstrated unanticipated resistance and tolerance to envelope-targeting antibiotics, which may be driven by rewired peptidoglycan machinery and may underlie therapeutic failure during antibiotic treatment.
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25
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Deletion of a previously uncharacterized lipoprotein lirL confers resistance to an inhibitor of type II signal peptidase in Acinetobacter baumannii. Proc Natl Acad Sci U S A 2022; 119:e2123117119. [PMID: 36099298 PMCID: PMC9499571 DOI: 10.1073/pnas.2123117119] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Inhibiting bacterial lipoprotein biosynthesis in Enterobacteriaceae is an attractive antibacterial strategy to target multidrug resistance, and mechanisms of resistance to prolipoprotein signal peptidase (LspA) inhibitors in Escherichia coli are relatively well understood. In contrast, it has been challenging to understand the mechanisms of resistance to LspA inhibitors in Acinetobacter baumannii due to the substantially lower inhibitor potencies and the lack of a homologous lpp gene. By increasing the antibacterial potency of the LspA inhibitor, globomycin, against wild-type A. baumannii, we were able to examine resistance to LspA inhibitors, resulting in the identification of a previously uncharacterized highly abundant lipoprotein, LspA inhibitor resistance lipoprotein. This study reveals insights into resistance mechanisms of A. baumannii against inhibitors of bacterial lipoprotein biosynthesis. Acinetobacter baumannii is a clinically important, predominantly health care–associated gram-negative bacterium with high rates of emerging resistance worldwide. Given the urgent need for novel antibacterial therapies against A. baumannii, we focused on inhibiting lipoprotein biosynthesis, a pathway that is essential for envelope biogenesis in gram-negative bacteria. The natural product globomycin, which inhibits the essential type II signal peptidase prolipoprotein signal peptidase (LspA), is ineffective against wild-type A. baumannii clinical isolates due to its poor penetration through the outer membrane. Here, we describe a globomycin analog, G5132, that is more potent against wild-type and clinical A. baumannii isolates. Mutations leading to G5132 resistance in A. baumannii map to the signal peptide of a single hypothetical gene, which we confirm encodes an alanine-rich lipoprotein and have renamed lirL (prolipoprotein signal peptidase inhibitor resistance lipoprotein). LirL is a highly abundant lipoprotein primarily localized to the inner membrane. Deletion of lirL leads to G5132 resistance, inefficient cell division, increased sensitivity to serum, and attenuated virulence. Signal peptide mutations that confer resistance to G5132 lead to the accumulation of diacylglyceryl-modified LirL prolipoprotein in untreated cells without significant loss in cell viability, suggesting that these mutations overcome a block in lipoprotein biosynthetic flux by decreasing LirL prolipoprotein substrate sensitivity to processing by LspA. This study characterizes a lipoprotein that plays a critical role in resistance to LspA inhibitors and validates lipoprotein biosynthesis as a antibacterial target in A. baumannii.
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26
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Basardeh E, Piri-Gavgani S, Soltanmohammadi B, Ghanei M, Omrani MD, Soezi M, Shokrgozar MA, Azizi M, Fateh A, Vaziri F, Siadat SD, Sharifzadeh Z, Rahimi-Jamnani F. Anti- Acinetobacter baumannii single-chain variable fragments show direct bactericidal activity. IRANIAN JOURNAL OF BASIC MEDICAL SCIENCES 2022; 25:1141-1149. [PMID: 36246061 PMCID: PMC9526879 DOI: 10.22038/ijbms.2022.64062.14106] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Accepted: 08/21/2022] [Indexed: 11/06/2022]
Abstract
Objectives The high resistance rate of Acinetobacter baumannii and the limited number of available antibiotics have prompted a worldwide effort to develop effective antimicrobial agents. Accordingly, identifying single-chain variable fragment antibodies (scFvs), capable of exerting direct antibacterial activity in an immune system-independent manner, may be making immunocompromised patients more susceptible to A. baumannii infections. Materials and Methods To isolate bactericidal scFvs targeting A. baumannii, we panned a large human scFv phage display library against whole-cell extensively drug-resistant (XDR) A. baumannii strains grown as biofilm or cultured with human blood or human peripheral blood mononuclear cells plus plasma. The binding of scFv-phages to A. baumannii was assessed by the dot-blot assay. Soluble scFvs, derived from the selected phages, were assessed based on their ability to bind and inhibit the growth of A. baumannii. Results Five phage clones showed the highest reactivity toward A. baumannii. Among five soluble scFvs, derived from positive phage clones, two scFvs, EB211 and EB279, had high expression yields and displayed strong binding to A. baumannii compared with the controls. Moreover, XDR A. baumannii strains treated with positively-charged scFvs, including EB211, EB279, or a cocktail of EB211 and EB279 (200 µg/ml), displayed lower viability (approximately 50%, 78%, and 40% viability, respectively) compared with PBS-treated bacteria. Conclusion These results suggest that combining last-resort antibiotics with bactericidal scFvs could provide promising outcomes in immunocompromised individuals with A. baumannii infections.
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Affiliation(s)
- Eilnaz Basardeh
- Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran, Iran, Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | - Somayeh Piri-Gavgani
- Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran, Iran, Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | - Behnoush Soltanmohammadi
- Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran, Iran, Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | - Mostafa Ghanei
- Chemical Injuries Research Center, Systems Biology and Poisoning Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Mir Davood Omrani
- Department of Medical Genetics, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mahdieh Soezi
- Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran, Iran, Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | | | - Masoumeh Azizi
- Molecular Medicine Department, Biotechnology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | - Abolfazl Fateh
- Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran, Iran, Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | - Farzam Vaziri
- Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran, Iran, Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | - Seyed Davar Siadat
- Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran, Iran, Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | | | - Fatemeh Rahimi-Jamnani
- Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran, Iran, Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran ,Corresponding author: Fatemeh Rahimi-Jamnani. Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran, Iran; Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran. Tel: +98-21-66953311; Fax: +98-21-66465132;
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Peptidoglycan Recycling Promotes Outer Membrane Integrity and Carbapenem Tolerance in Acinetobacter baumannii. mBio 2022; 13:e0100122. [PMID: 35638738 PMCID: PMC9239154 DOI: 10.1128/mbio.01001-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
β-Lactam antibiotics exploit the essentiality of the bacterial cell envelope by perturbing the peptidoglycan layer, typically resulting in rapid lysis and death. Many Gram-negative bacteria do not lyse but instead exhibit "tolerance," the ability to sustain viability in the presence of bactericidal antibiotics for extended periods. Antibiotic tolerance has been implicated in treatment failure and is a stepping-stone in the acquisition of true resistance, and the molecular factors that promote intrinsic tolerance are not well understood. Acinetobacter baumannii is a critical-threat nosocomial pathogen notorious for its ability to rapidly develop multidrug resistance. Carbapenem β-lactam antibiotics (i.e., meropenem) are first-line prescriptions to treat A. baumannii infections, but treatment failure is increasingly prevalent. Meropenem tolerance in Gram-negative pathogens is characterized by morphologically distinct populations of spheroplasts, but the impact of spheroplast formation is not fully understood. Here, we show that susceptible A. baumannii clinical isolates demonstrate tolerance to high-level meropenem treatment, form spheroplasts upon exposure to the antibiotic, and revert to normal growth after antibiotic removal. Using transcriptomics and genetic screens, we show that several genes associated with outer membrane integrity maintenance and efflux promote tolerance, likely by limiting entry into the periplasm. Genes associated with peptidoglycan homeostasis in the periplasm and cytoplasm also answered our screen, and their disruption compromised cell envelope barrier function. Finally, we defined the enzymatic activity of the tolerance determinants penicillin-binding protein 7 (PBP7) and ElsL (a cytoplasmic ld-carboxypeptidase). These data show that outer membrane integrity and peptidoglycan recycling are tightly linked in their contribution to A. baumannii meropenem tolerance. IMPORTANCE Carbapenem treatment failure associated with "superbug" infections has rapidly increased in prevalence, highlighting the urgent need to develop new therapeutic strategies. Antibiotic tolerance can directly lead to treatment failure but has also been shown to promote the acquisition of true resistance within a population. While some studies have addressed mechanisms that promote tolerance, factors that underlie Gram-negative bacterial survival during carbapenem treatment are not well understood. Here, we characterized the role of peptidoglycan recycling in outer membrane integrity maintenance and meropenem tolerance in A. baumannii. These studies suggest that the pathogen limits antibiotic concentrations in the periplasm and highlight physiological processes that could be targeted to improve antimicrobial treatment.
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Abstract
The outer membrane (OM) of Gram-negative bacteria is an essential organelle that acts as a formidable barrier to antibiotics. Increasingly prevalent resistance to existing drugs has exacerbated the need for antibiotic discovery efforts targeting the OM. Acylated proteins, known as lipoproteins, are essential in every pathway needed to build the OM. The central role of OM lipoproteins makes their biogenesis a uniquely attractive therapeutic target, but it also complicates in vivo identification of on-pathway inhibitors, as inhibition of OM lipoprotein biogenesis broadly disrupts OM assembly. Here, we use genetics to probe the eight essential proteins involved in OM lipoprotein maturation and trafficking. We define a biological signature consisting of three simple assays that can characteristically identify OM lipoprotein biogenesis defects in vivo. We find that several known chemical inhibitors of OM lipoprotein biogenesis conform to the biological signature. We also examine MAC13243, a proposed inhibitor of OM lipoprotein biogenesis, and find that it fails to conform to the biological signature. Indeed, we demonstrate that MAC13243 activity relies entirely on a target outside of the OM lipoprotein biogenesis pathway. Hence, our signature offers simple tools to easily assess whether antibiotic lead compounds target an essential pathway that is the hub of OM assembly.
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29
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Chen Y, Yang H, Luo S, Wang L, Lu S, Fu Z. Engineering Phage Tail Fiber Protein as a Wide-Spectrum Probe for Acinetobacter baumannii Strains with a Recognition Rate of 100. Anal Chem 2022; 94:9610-9617. [PMID: 35749272 DOI: 10.1021/acs.analchem.2c00682] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
As a multidrug-resistant pathogen, Acinetobacter baumannii has long been identified as one of the most common nosocomial bacteria. High-performance recognition probes for wide-spectrum detection of A. baumannii are highly desired to achieve efficient diagnosis and timely treatment of infectious diseases induced by this pathogen. An engineering tail fiber protein (ETFP) named as Gp50 encoded by lytic phage Abp9 was expressed in Escherichia coli and identified as a binding protein for A. baumannii. According to the results of genome sequencing of an A. baumannii wild strain and phage-resistant strains, the binding receptor of ETFP Gp50 is inferred to be a lipopolysaccharide distributed on the bacterial surface. The engineering protein did not show lytic activity to A. baumannii, which facilitates the development of reliable diagnosis kits and biosensors with high flexibility and low false-negative rate. The results of specificity study show that ETFP Gp50 is a species-specific binding protein with a recognition rate of 100% for all tested 77 A. baumannii strains, while that of the natural phage Abp9 is only 27.3%. With the engineering protein, a fluorescence method was developed to detect A. baumannii with a detection range of 2.0 × 102 to 2.0 × 108 cfu mL-1. The method has been used for the quantification of A. baumannii in a diverse sample matrix with acceptable reliability. The work demonstrates the application potential of ETFP Gp50 as an ideal recognition probe for rapid screening of A. baumannii strains in a complicated sample matrix.
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Affiliation(s)
- Ying Chen
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Ministry of Education), College of Pharmaceutical Sciences, Southwest University, Chongqing 400715, China
| | - Honglin Yang
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Ministry of Education), College of Pharmaceutical Sciences, Southwest University, Chongqing 400715, China
| | - Shuai Luo
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Ministry of Education), College of Pharmaceutical Sciences, Southwest University, Chongqing 400715, China
| | - Lin Wang
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Ministry of Education), College of Pharmaceutical Sciences, Southwest University, Chongqing 400715, China
| | - Shuguang Lu
- Department of Microbiology, College of Basic Medical Science, Army Medical University, Chongqing 400038, China
| | - Zhifeng Fu
- Key Laboratory of Luminescence Analysis and Molecular Sensing (Ministry of Education), College of Pharmaceutical Sciences, Southwest University, Chongqing 400715, China
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30
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Zik JJ, Yoon SH, Guan Z, Stankeviciute Skidmore G, Gudoor RR, Davies KM, Deutschbauer AM, Goodlett DR, Klein EA, Ryan KR. Caulobacter lipid A is conditionally dispensable in the absence of fur and in the presence of anionic sphingolipids. Cell Rep 2022; 39:110888. [PMID: 35649364 PMCID: PMC9393093 DOI: 10.1016/j.celrep.2022.110888] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 03/29/2022] [Accepted: 05/06/2022] [Indexed: 01/12/2023] Open
Abstract
Lipid A, the membrane-anchored portion of lipopolysaccharide (LPS), is an essential component of the outer membrane (OM) of nearly all Gram-negative bacteria. Here we identify regulatory and structural factors that together render lipid A nonessential in Caulobacter crescentus. Mutations in the ferric uptake regulator fur allow Caulobacter to survive in the absence of either LpxC, which catalyzes an early step of lipid A synthesis, or CtpA, a tyrosine phosphatase homolog we find is needed for wild-type lipid A structure and abundance. Alterations in Fur-regulated processes, rather than iron status per se, underlie the ability to survive when lipid A synthesis is blocked. Fitness of lipid A-deficient Caulobacter requires an anionic sphingolipid, ceramide phosphoglycerate (CPG), which also mediates sensitivity to the antibiotic colistin. Our results demonstrate that, in an altered regulatory landscape, anionic sphingolipids can support the integrity of a lipid A-deficient OM. Lipid A, the membrane-anchoring segment of lipopolysaccharide, is generally considered to be an essential component of the Gram-negative bacterial outer membrane. Zik et al. show that deletion of the transcriptional regulator fur and synthesis of the anionic sphingolipid ceramide phosphoglycerate enable Caulobacter crescentus to survive without lipid A.
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Affiliation(s)
- Justin J Zik
- Department of Plant & Microbial Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Sung Hwan Yoon
- Department of Microbial Pathogenesis, University of Maryland School of Dentistry, Baltimore, MD 21201, USA
| | - Ziqiang Guan
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
| | - Gabriele Stankeviciute Skidmore
- Center for Computational and Integrative Biology, Rutgers University-Camden, Camden, NJ 08102, USA; Rutgers Center for Lipid Research, Rutgers University, New Brunswick, NJ 08901, USA
| | - Ridhi R Gudoor
- Molecular Biosciences and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Karen M Davies
- Molecular Biosciences and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Adam M Deutschbauer
- Environmental Genomics & Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - David R Goodlett
- Department of Microbial Pathogenesis, University of Maryland School of Dentistry, Baltimore, MD 21201, USA; Department of Biochemistry & Microbiology, University of Victoria, Victoria, BC V8W 2Y2, Canada; University of Victoria-Genome BC Proteomics Centre, Victoria, BC V8Z 7X8, Canada
| | - Eric A Klein
- Center for Computational and Integrative Biology, Rutgers University-Camden, Camden, NJ 08102, USA; Biology Department, Rutgers University-Camden, Camden, NJ 08102, USA; Rutgers Center for Lipid Research, Rutgers University, New Brunswick, NJ 08901, USA
| | - Kathleen R Ryan
- Department of Plant & Microbial Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Environmental Genomics & Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
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Glover JS, Browning BD, Ticer TD, Engevik AC, Engevik MA. Acinetobacter calcoaceticus is Well Adapted to Withstand Intestinal Stressors and Modulate the Gut Epithelium. Front Physiol 2022; 13:880024. [PMID: 35685287 PMCID: PMC9170955 DOI: 10.3389/fphys.2022.880024] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Accepted: 04/12/2022] [Indexed: 12/22/2022] Open
Abstract
Background: The gastrointestinal tract has been speculated to serve as a reservoir for Acinetobacter, however little is known about the ecological fitness of Acinetobacter strains in the gut. Likewise, not much is known about the ability of Acinetobacter to consume dietary, or host derived nutrients or their capacity to modulate host gene expression. Given the increasing prevalence of Acinetobacter in the clinical setting, we sought to characterize how A. calcoaceticus responds to gut-related stressors and identify potential microbe-host interactions. Materials and Methods: To accomplish these aims, we grew clinical isolates and commercially available strains of A. calcoaceticus in minimal media with different levels of pH, osmolarity, ethanol and hydrogen peroxide. Utilization of nutrients was examined using Biolog phenotypic microarrays. To examine the interactions of A. calcoaceticus with the host, inverted murine organoids where the apical membrane is exposed to bacteria, were incubated with live A. calcoaceticus, and gene expression was examined by qPCR. Results: All strains grew modestly at pH 6, 5 and 4; indicating that these strains could tolerate passage through the gastrointestinal tract. All strains had robust growth in 0.1 and 0.5 M NaCl concentrations which mirror the small intestine, but differences were observed between strains in response to 1 M NaCl. Additionally, all strains tolerated up to 5% ethanol and 0.1% hydrogen peroxide. Biolog phenotypic microarrays revealed that A. calcoaceticus strains could use a range of nutrient sources, including monosaccharides, disaccharides, polymers, glycosides, acids, and amino acids. Interestingly, the commercially available A. calcoaceticus strains and one clinical isolate stimulated the pro-inflammatory cytokines Tnf, Kc, and Mcp-1 while all strains suppressed Muc13 and Muc2. Conclusion: Collectively, these data demonstrate that A. calcoaceticus is well adapted to dealing with environmental stressors of the gastrointestinal system. This data also points to the potential for Acinetobacter to influence the gut epithelium.
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Affiliation(s)
- Janiece S. Glover
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC, United States
| | - Brittney D. Browning
- Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, SC, United States
| | - Taylor D. Ticer
- Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC, United States
| | - Amy C. Engevik
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC, United States
| | - Melinda A. Engevik
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC, United States
- Department of Microbiology and Immunology, Medical University of South Carolina, Charleston, SC, United States
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Abstract
Small molecule adjuvants that enhance the activity of established antibiotics represent promising agents in the battle against antibiotic resistance. Adjuvants generally act by inhibiting antibiotic resistance processes, and specifying the process acted on is a critical step in defining an adjuvant's mechanism of action. This step is typically carried out biochemically by identifying molecules that bind adjuvants and then inferring their roles in resistance. Here, we present a complementary genetic strategy based on identifying mutations that both sensitize cells to antibiotic and make them "adjuvant blind." We tested the approach in Acinetobacter baumannii AB5075 using two adjuvants: a well-characterized β-lactamase inhibitor (avibactam) and a compound enhancing outer membrane permeability (aryl 2-aminoimidazole AI-1). The avibactam studies showed that the adjuvant potentiated one β-lactam (ceftazidime) through action on a single β-lactamase (GES-14) and a second (meropenem) by targeting two different enzymes (GES-14 and OXA-23). Mutations impairing disulfide bond formation (DsbAB) also reduced potentiation, possibly by impairing β-lactamase folding. Mutations reducing AI-1 potentiation of canonical Gram-positive antibiotics (vancomycin and clarithromycin) blocked lipooligosaccharide (LOS/LPS) synthesis or its acyl modification. The results indicate that LOS-mediated outer membrane impermeability is targeted by the adjuvant and show the importance of acylation in the resistance. As part of the study, we employed Acinetobacter baylyi as a model to verify the generality of the A. baumannii results and identified the principal resistance genes for ceftazidime, meropenem, vancomycin, and clarithromycin in A. baumannii AB5075. Overall, the work provides a foundation for analyzing adjuvant action using a comprehensive genetic approach. IMPORTANCE One strategy to confront the antibiotic resistance crisis is through the development of adjuvant compounds that increase the efficacy of established drugs. A key step in the development of a natural product adjuvant as a drug is identifying the resistance process it undermines to enhance antibiotic activity. Previous procedures designed to accomplish this have relied on biochemical identification of cell components that bind adjuvant. Here, we present a complementary strategy based on identifying mutations that eliminate adjuvant activity.
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Ledger EVK, Sabnis A, Edwards AM. Polymyxin and lipopeptide antibiotics: membrane-targeting drugs of last resort. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 35118938 PMCID: PMC8941995 DOI: 10.1099/mic.0.001136] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The polymyxin and lipopeptide classes of antibiotics are membrane-targeting drugs of last resort used to treat infections caused by multi-drug-resistant pathogens. Despite similar structures, these two antibiotic classes have distinct modes of action and clinical uses. The polymyxins target lipopolysaccharide in the membranes of most Gram-negative species and are often used to treat infections caused by carbapenem-resistant species such as Escherichia coli, Acinetobacter baumannii and Pseudomonas aeruginosa. By contrast, the lipopeptide daptomycin requires membrane phosphatidylglycerol for activity and is only used to treat infections caused by drug-resistant Gram-positive bacteria such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. However, despite having distinct targets, both antibiotic classes cause membrane disruption, are potently bactericidal in vitro and share similarities in resistance mechanisms. Furthermore, there are concerns about the efficacy of these antibiotics, and there is increasing interest in using both polymyxins and daptomycin in combination therapies to improve patient outcomes. In this review article, we will explore what is known about these distinct but structurally similar classes of antibiotics, discuss recent advances in the field and highlight remaining gaps in our knowledge.
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Affiliation(s)
- Elizabeth V K Ledger
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Rd, London, SW7 2AZ, UK
| | - Akshay Sabnis
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Rd, London, SW7 2AZ, UK
| | - Andrew M Edwards
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, Armstrong Rd, London, SW7 2AZ, UK
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Murtha AN, Kazi MI, Schargel RD, Cross T, Fihn C, Cattoir V, Carlson EE, Boll JM, Dörr T. High-level carbapenem tolerance requires antibiotic-induced outer membrane modifications. PLoS Pathog 2022; 18:e1010307. [PMID: 35130322 PMCID: PMC8853513 DOI: 10.1371/journal.ppat.1010307] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 02/17/2022] [Accepted: 01/26/2022] [Indexed: 12/22/2022] Open
Abstract
Antibiotic tolerance is an understudied potential contributor to antibiotic treatment failure and the emergence of multidrug-resistant bacteria. The molecular mechanisms governing tolerance remain poorly understood. A prominent type of β-lactam tolerance relies on the formation of cell wall-deficient spheroplasts, which maintain structural integrity via their outer membrane (OM), an asymmetric lipid bilayer consisting of phospholipids on the inner leaflet and a lipid-linked polysaccharide (lipopolysaccharide, LPS) enriched in the outer monolayer on the cell surface. How a membrane structure like LPS, with its reliance on mere electrostatic interactions to maintain stability, is capable of countering internal turgor pressure is unknown. Here, we have uncovered a novel role for the PhoPQ two-component system in tolerance to the β-lactam antibiotic meropenem in Enterobacterales. We found that PhoPQ is induced by meropenem treatment and promotes an increase in 4-amino-4-deoxy-L-aminoarabinose [L-Ara4N] modification of lipid A, the membrane anchor of LPS. L-Ara4N modifications likely enhance structural integrity, and consequently tolerance to meropenem, in several Enterobacterales species. Importantly, mutational inactivation of the negative PhoPQ regulator mgrB (commonly selected for during clinical therapy with the last-resort antibiotic colistin, an antimicrobial peptide [AMP]) results in dramatically enhanced tolerance, suggesting that AMPs can collaterally select for meropenem tolerance via stable overactivation of PhoPQ. Lastly, we identify histidine kinase inhibitors (including an FDA-approved drug) that inhibit PhoPQ-dependent LPS modifications and consequently potentiate meropenem to enhance lysis of tolerant cells. In summary, our results suggest that PhoPQ-mediated LPS modifications play a significant role in stabilizing the OM, promoting survival when the primary integrity maintenance structure, the cell wall, is removed. Treating an infection with an antibiotic often fails, resulting in a tremendous public health burden. One understudied likely reason for treatment failure is the development of “antibiotic tolerance”, the ability of bacteria to survive normally lethal exposure to an antibiotic. Here, we describe a molecular mechanism promoting tolerance. A bacterial stress sensor (PhoPQ) is activated in response to antibiotic (meropenem) treatment and consequently strengthens a bacterial protective “shell” to enhance survival. We also identify inhibitors of this mechanism, opening the door to developing compounds that help antibiotics work better against tolerant bacteria.
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Affiliation(s)
- Andrew N. Murtha
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, United States of America
- Department of Microbiology, Cornell University, Ithaca, New York, United States of America
| | - Misha I. Kazi
- Department of Biology, University of Texas Arlington, Arlington, Texas, United States of America
| | - Richard D. Schargel
- Department of Biology, University of Texas Arlington, Arlington, Texas, United States of America
| | - Trevor Cross
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, United States of America
- Department of Microbiology, Cornell University, Ithaca, New York, United States of America
| | - Conrad Fihn
- Department of Medicinal Chemistry, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Vincent Cattoir
- Department of Clinical Microbiology and National Reference Center for Antimicrobial Resistance (Lab Enterococci), Rennes University Hospital, Rennes, France; Inserm Unit U1230, University of Rennes 1, Rennes, France
| | - Erin E. Carlson
- Department of Medicinal Chemistry, University of Minnesota, Minneapolis, Minnesota, United States of America
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota, United States of America
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, Minnesota, United States of America
- Department of Molecular Pharmacology and Therapeutics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Joseph M. Boll
- Department of Biology, University of Texas Arlington, Arlington, Texas, United States of America
- * E-mail: (JMB); (TD)
| | - Tobias Dörr
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, New York, United States of America
- Department of Microbiology, Cornell University, Ithaca, New York, United States of America
- Cornell Institute of Host-Microbe Interactions and Disease, Cornell University, Ithaca, New York, United States of America
- * E-mail: (JMB); (TD)
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Toth M, Lee M, Stewart NK, Vakulenko SB. Effects of Inactivation of d,d-Transpeptidases of Acinetobacter baumannii on Bacterial Growth and Susceptibility to β-Lactam Antibiotics. Antimicrob Agents Chemother 2022; 66:e0172921. [PMID: 34780270 PMCID: PMC8765447 DOI: 10.1128/aac.01729-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 11/12/2021] [Indexed: 11/20/2022] Open
Abstract
Resistance to β-lactams, the most used antibiotics worldwide, constitutes the major problem for the treatment of bacterial infections. In the nosocomial pathogen Acinetobacter baumannii, β-lactamase-mediated resistance to the carbapenem family of β-lactam antibiotics has resulted in the selection and dissemination of multidrug-resistant isolates, which often cause infections characterized by high mortality rates. There is thus an urgent demand for new β-lactamase-resistant antibiotics that also inhibit their targets, penicillin-binding proteins (PBPs). As some PBPs are indispensable for the biosynthesis of the bacterial cell wall and survival, we evaluated their importance for the growth of A. baumannii by performing gene inactivation studies of d,d-transpeptidase domains of high-molecular-mass (HMM) PBPs individually and in combination with one another. We show that PBP3 is essential for A. baumannii survival, as deletion mutants of this d,d-transpeptidase were not viable. The inactivation of PBP1a resulted in partial cell lysis and retardation of bacterial growth, and these effects were further enhanced by the additional inactivation of PBP2 but not PBP1b. Susceptibility to β-lactam antibiotics increased 4- to 8-fold for the A. baumannii PBP1a/PBP1b/PBP2 triple mutant and 2- to 4-fold for all remaining mutants. Analysis of the peptidoglycan structure revealed a significant change in the muropeptide composition of the triple mutant and demonstrated that the lack of d,d-transpeptidase activity of PBP1a, PBP1b, and PBP2 is compensated for by an increase in the l,d-transpeptidase-mediated cross-linking activity of LdtJ. Overall, our data showed that in addition to essential PBP3, the simultaneous inhibition of PBP1a and PBP2 or PBPs in combination with LdtJ could represent potential strategies for the design of novel drugs against A. baumannii.
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Affiliation(s)
- Marta Toth
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
| | - Mijoon Lee
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
- Mass Spectrometry and Proteomics Facility, University of Notre Dame, Notre Dame, Indiana, USA
| | - Nichole K. Stewart
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
| | - Sergei B. Vakulenko
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
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Böhringer N, Green R, Liu Y, Mettal U, Marner M, Modaresi SM, Jakob RP, Wuisan ZG, Maier T, Iinishi A, Hiller S, Lewis K, Schäberle TF. Mutasynthetic Production and Antimicrobial Characterization of Darobactin Analogs. Microbiol Spectr 2021; 9:e0153521. [PMID: 34937193 PMCID: PMC8694152 DOI: 10.1128/spectrum.01535-21] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 11/15/2021] [Indexed: 12/15/2022] Open
Abstract
There is great need for therapeutics against multidrug-resistant, Gram-negative bacterial pathogens. Recently, darobactin A, a novel bicyclic heptapeptide that selectively kills Gram-negative bacteria by targeting the outer membrane protein BamA, was discovered. Its efficacy was proven in animal infection models of Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa, thus promoting darobactin A as a promising lead compound. Originally discovered from members of the nematode-symbiotic genus Photorhabdus, the biosynthetic gene cluster (BGC) encoding the synthesis of darobactin A can also be found in other members of the class Gammaproteobacteria. Therein, the precursor peptides DarB to -F, which differ in their core sequence from darobactin A, were identified in silico. Even though production of these analogs was not observed in the putative producer strains, we were able to generate them by mutasynthetic derivatization of a heterologous expression system. The analogs generated were isolated and tested for their bioactivity. The most potent compound, darobactin B, was used for cocrystallization with the target BamA, revealing a binding site identical to that of darobactin A. Despite its potency, darobactin B did not exhibit cytotoxicity, and it was slightly more active against Acinetobacter baumannii isolates than darobactin A. Furthermore, we evaluated the plasma protein binding of darobactin A and B, indicating their different pharmacokinetic properties. This is the first report on new members of this new antibiotic class, which is likely to expand to several promising therapeutic candidates. IMPORTANCE Therapeutic options to combat Gram-negative bacterial pathogens are dwindling with increasing antibiotic resistance. This study presents a proof of concept for the heterologous-expression approach to expand on the novel antibiotic class of darobactins and to generate analogs with different activities and pharmacokinetic properties. In combination with the structural data of the target BamA, this approach may contribute to structure-activity relationship (SAR) data to optimize inhibitors of this essential outer membrane protein of Gram-negative pathogens.
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Affiliation(s)
- Nils Böhringer
- Justus-Liebig-University Gießen, Gießen, Germany
- German Center of Infection Research (DZIF), Partner Site Gießen-Marburg-Langen, Gießen, Germany
| | - Robert Green
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Yang Liu
- Justus-Liebig-University Gießen, Gießen, Germany
| | - Ute Mettal
- Justus-Liebig-University Gießen, Gießen, Germany
| | - Michael Marner
- Fraunhofer Institute for Molecular Biology and Applied Ecology, Branch for Bioresources, Gießen, Germany
| | | | | | | | - Timm Maier
- Biozentrum, University of Basel, Basel, Switzerland
| | - Akira Iinishi
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | | | - Kim Lewis
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Till F. Schäberle
- Justus-Liebig-University Gießen, Gießen, Germany
- German Center of Infection Research (DZIF), Partner Site Gießen-Marburg-Langen, Gießen, Germany
- Fraunhofer Institute for Molecular Biology and Applied Ecology, Branch for Bioresources, Gießen, Germany
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A New Class of Cell Wall-Recycling l,d-Carboxypeptidase Determines β-Lactam Susceptibility and Morphogenesis in Acinetobacter baumannii. mBio 2021; 12:e0278621. [PMID: 34872350 PMCID: PMC8649774 DOI: 10.1128/mbio.02786-21] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The hospital-acquired pathogen Acinetobacter baumannii possesses a complex cell envelope that is key to its multidrug resistance and virulence. The bacterium, however, lacks many canonical enzymes that build the envelope in model organisms. Instead, A. baumannii contains a number of poorly annotated proteins that may allow alternative mechanisms of envelope biogenesis. We demonstrated previously that one of these unusual proteins, ElsL, is required for maintaining a characteristic short rod shape and for withstanding antibiotics that attack the septal cell wall. Curiously, ElsL is composed of a leaderless YkuD-family domain usually found in secreted, cell wall-modifying l,d-transpeptidases (LDTs). Here, we show that, rather than being an LDT, ElsL is actually a new class of cytoplasmic l,d-carboxypeptidase (LDC) that provides a critical step in cell wall recycling previously thought to be missing from A. baumannii. Absence of ElsL impairs cell wall integrity, morphology, and intrinsic resistance due to buildup of murein tetrapeptide precursors, toxicity of which is bypassed by preventing muropeptide recycling. Multiple pathways in the cell become sites of vulnerability when ElsL is inactivated, including l,d-cross-link formation, cell division, and outer membrane lipid homoeostasis, reflecting its pleiotropic influence on envelope physiology. We thus reveal a novel class of cell wall-recycling LDC critical to growth and homeostasis of A. baumannii and likely many other bacteria.
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Acinetobacter baumannii Can Survive with an Outer Membrane Lacking Lipooligosaccharide Due to Structural Support from Elongasome Peptidoglycan Synthesis. mBio 2021; 12:e0309921. [PMID: 34844428 PMCID: PMC8630537 DOI: 10.1128/mbio.03099-21] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gram-negative bacteria resist external stresses due to cell envelope rigidity, which is provided by two membranes and a peptidoglycan layer. The outer membrane (OM) surface contains lipopolysaccharide (LPS; contains O-antigen) or lipooligosaccharide (LOS). LPS/LOS are essential in most Gram-negative bacteria and may contribute to cellular rigidity. Acinetobacter baumannii is a useful tool for testing these hypotheses as it can survive without LOS. Previously, our group found that strains with naturally high levels of penicillin binding protein 1A (PBP1A) could not become LOS deficient unless the gene encoding it was deleted, highlighting the relevance of peptidoglycan biosynthesis and suggesting that high PBP1A levels were toxic during LOS deficiency. Transposon sequencing and follow-up analysis found that axial peptidoglycan synthesis by the elongasome and a peptidoglycan recycling enzyme, ElsL, were vital in LOS-deficient cells. The toxicity of high PBP1A levels during LOS deficiency was clarified to be due to a negative impact on elongasome function. Our data suggest that during LOS deficiency, the strength of the peptidoglycan specifically imparted by elongasome synthesis becomes essential, supporting that the OM and peptidoglycan contribute to cell rigidity.
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Equisetin Restores Colistin Sensitivity against Multi-Drug Resistant Gram-Negative Bacteria. Antibiotics (Basel) 2021; 10:antibiotics10101263. [PMID: 34680843 PMCID: PMC8532683 DOI: 10.3390/antibiotics10101263] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Revised: 10/07/2021] [Accepted: 10/13/2021] [Indexed: 11/17/2022] Open
Abstract
The overuse of antibiotics and the scarcity of new drugs have led to a serious antimicrobial resistance crisis, especially for multi-drug resistant (MDR) Gram-negative bacteria. In the present study, we investigated the antimicrobial activity of a marine antibiotic equisetin in combination with colistin against Gram-negative bacteria and explored the mechanisms of synergistic activity. We tested the synergistic effect of equisetin in combination with colistin on 23 clinical mcr-1 positive isolates and found that 4 µg/mL equisetin combined with 1 µg/mL colistin showed 100% inhibition. Consistently, equisetin restored the sensitivity of 10 species of mcr-1 positive Gram-negative bacteria to colistin. The combination of equisetin and colistin quickly killed 99.9% bacteria in one hour in time-kill assays. We found that colistin promoted intracellular accumulation of equisetin in colistin-resistant E. coli based on LC-MS/MS analysis. Interestingly, equisetin boosted ROS accumulation in E. coli in the presence of colistin. Moreover, we found that equisetin and colistin lost the synergistic effect in two LPS-deficient A. baumannii strains. These findings suggest that colistin destroys the hydrophobic barrier of Gram-negative bacteria, facilitating equisetin to enter the cell and exert its antibacterial effect. Lastly, equisetin restored the activity of colistin in a G. mellonella larvae infection model. Collectively, these results reveal that equisetin can potentiate colistin activity against MDR Gram-negative bacteria including colistin-resistant strains, providing an alternative approach to address Gram-negative pathogens associated with infections in clinics.
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Kumar S, Anwer R, Azzi A. Virulence Potential and Treatment Options of Multidrug-Resistant (MDR) Acinetobacter baumannii. Microorganisms 2021; 9:microorganisms9102104. [PMID: 34683425 PMCID: PMC8541637 DOI: 10.3390/microorganisms9102104] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 09/18/2021] [Accepted: 09/21/2021] [Indexed: 12/12/2022] Open
Abstract
Acinetobacter baumannii is an opportunistic pathogen which is undoubtedly known for a high rate of morbidity and mortality in hospital-acquired infections. A. baumannii causes life-threatening infections, including; ventilator-associated pneumonia (VAP), meningitis, bacteremia, and wound and urinary tract infections (UTI). In 2017, the World Health Organization listed A. baumannii as a priority-1 pathogen. The prevalence of A. baumannii infections and outbreaks emphasizes the direct need for the use of effective therapeutic agents for treating such infections. Available antimicrobials, such as; carbapenems, tigecycline, and colistins have insufficient effectiveness due to the appearance of multidrug-resistant strains, accentuating the need for alternative and novel therapeutic remedies. To understand and overcome this menace, the knowledge of recent discoveries on the virulence factors of A. baumannii is needed. Herein, we summarized the role of various virulence factors, including; outer membrane proteins, efflux pumps, biofilm, penicillin-binding proteins, and siderophores/iron acquisition systems. We reviewed the recent scientific literature on different A. baumannii virulence factors and the effective antimicrobial agents for the treatment and management of bacterial infections.
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Affiliation(s)
- Sunil Kumar
- Department of Biotechnology, Maharishi Markandeshwar (Deemed to Be University), Mullana, Ambala 133207, India;
| | - Razique Anwer
- Department of Pathology, College of Medicine, Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh 13317-4233, Saudi Arabia;
| | - Arezki Azzi
- Department of Biochemistry, College of Medicine, Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh 13317-4233, Saudi Arabia
- Correspondence:
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Yin W, Ling Z, Dong Y, Qiao L, Shen Y, Liu Z, Wu Y, Li W, Zhang R, Walsh TR, Dai C, Li J, Yang H, Liu D, Wang Y, Gao GF, Shen J. Mobile Colistin Resistance Enzyme MCR-3 Facilitates Bacterial Evasion of Host Phagocytosis. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:e2101336. [PMID: 34323389 PMCID: PMC8456205 DOI: 10.1002/advs.202101336] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 06/12/2021] [Indexed: 05/10/2023]
Abstract
Mobile colistin resistance enzyme MCR-3 is a phosphoethanolamine transferase modifying lipid A in Gram-negative bacteria. MCR-3 generally mediates low-level (≤8 mg L-1 ) colistin resistance among Enterobacteriaceae, but occasionally confers high-level (>128 mg L-1 ) resistance in aeromonads. Herein, it is determined that MCR-3, together with another lipid A modification mediated by the arnBCADTEF operon, may be responsible for high-level colistin resistance in aeromonads. Lipid A is the critical site of pathogens for Toll-like receptor 4 recognizing. However, it is unknown whether or how MCR-3-mediated lipid A modification affects the host immune response. Compared with the wild-type strains, increased mortality is observed in mice intraperitoneally-infected with mcr-3-positive Aeromonas salmonicida and Escherichia coli strains, along with sepsis symptoms. Further, mcr-3-positive strains show decreased clearance rates than wild-type strains, leading to bacterial accumulation in organs. The increased mortality is tightly associated with the increased tissue hypoxia, injury, and post-inflammation. MCR-3 expression also impairs phagocytosis efficiency both in vivo and in vitro, contributing to the increased persistence of mcr-3-positive bacteria in tissues compared with parental strains. This study, for the first time, reveals a dual function of MCR-3 in bacterial resistance and pathogenicity, which calls for caution in treating the infections caused by mcr-positive pathogens.
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Affiliation(s)
- Wenjuan Yin
- Beijing Key Laboratory of Detection Technology for Animal‐Derived Food SafetyCollege of Veterinary MedicineChina Agricultural UniversityBeijing100193China
- College of Basic Medical ScienceKey Laboratory of Pathogenesis Mechanism and Control of Inflammatory‐Autoimmune Diseases of Hebei ProvinceHebei UniversityBaoding071002China
| | - Zhuoren Ling
- Beijing Key Laboratory of Detection Technology for Animal‐Derived Food SafetyCollege of Veterinary MedicineChina Agricultural UniversityBeijing100193China
| | - Yanjun Dong
- Department of Basic Veterinary MedicineCollege of Veterinary MedicineChina Agricultural UniversityHaidianBeijing100193China
| | - Lu Qiao
- Beijing Key Laboratory of Detection Technology for Animal‐Derived Food SafetyCollege of Veterinary MedicineChina Agricultural UniversityBeijing100193China
| | - Yingbo Shen
- CAS Key Laboratory of Pathogenic Microbiology and ImmunologyInstitute of MicrobiologyChinese Academy of Sciences (CAS)Beijing100101China
| | - Zhihai Liu
- Beijing Key Laboratory of Detection Technology for Animal‐Derived Food SafetyCollege of Veterinary MedicineChina Agricultural UniversityBeijing100193China
- Agricultural Bio‐Pharmaceutical LaboratoryCollege of Chemistry and Pharmaceutical SciencesQingdao Agricultural UniversityQingdao266109China
| | - Yifan Wu
- Beijing Key Laboratory of Detection Technology for Animal‐Derived Food SafetyCollege of Veterinary MedicineChina Agricultural UniversityBeijing100193China
| | - Wan Li
- Beijing Key Laboratory of Detection Technology for Animal‐Derived Food SafetyCollege of Veterinary MedicineChina Agricultural UniversityBeijing100193China
| | - Rong Zhang
- The Second Affiliated Hospital of Zhejiang UniversityZhejiang UniversityHangzhou310009China
| | | | - Chongshan Dai
- Beijing Key Laboratory of Detection Technology for Animal‐Derived Food SafetyCollege of Veterinary MedicineChina Agricultural UniversityBeijing100193China
| | - Juan Li
- State Key Laboratory of Infectious Disease Prevention and ControlNational Institute for Communicable Disease Control and PreventionChinese Center for Disease Control and PreventionChangpingBeijing102206China
| | - Hui Yang
- NHC Key Laboratory of Food Safety Risk AssessmentChina National Center for Food Safety Risk AssessmentNo. 7 Panjiayuan NanliBeijing100021China
| | - Dejun Liu
- Beijing Key Laboratory of Detection Technology for Animal‐Derived Food SafetyCollege of Veterinary MedicineChina Agricultural UniversityBeijing100193China
| | - Yang Wang
- Beijing Key Laboratory of Detection Technology for Animal‐Derived Food SafetyCollege of Veterinary MedicineChina Agricultural UniversityBeijing100193China
| | - George Fu Gao
- CAS Key Laboratory of Pathogenic Microbiology and ImmunologyInstitute of MicrobiologyChinese Academy of Sciences (CAS)Beijing100101China
- College of Veterinary MedicineChina Agricultural UniversityHaidianBeijing100193China
| | - Jianzhong Shen
- Beijing Key Laboratory of Detection Technology for Animal‐Derived Food SafetyCollege of Veterinary MedicineChina Agricultural UniversityBeijing100193China
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Yoon EJ, Jeong SH. MALDI-TOF Mass Spectrometry Technology as a Tool for the Rapid Diagnosis of Antimicrobial Resistance in Bacteria. Antibiotics (Basel) 2021; 10:antibiotics10080982. [PMID: 34439032 PMCID: PMC8388893 DOI: 10.3390/antibiotics10080982] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 08/09/2021] [Accepted: 08/12/2021] [Indexed: 12/17/2022] Open
Abstract
Species identification by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a routine diagnostic process for infectious diseases in current clinical settings. The rapid, low-cost, and simple to conduct methodology is expanding its application in clinical microbiology laboratories to diagnose the antimicrobial resistance (AMR) in microorganisms. Primarily, antimicrobial susceptibility testing is able to be carried out either by comparing the area under curve of MALDI spectra of bacteria grown in media with antimicrobial drugs or by identifying the shift peaks of bacteria grown in media including 13C isotope with antimicrobial drugs. Secondly, the antimicrobial resistance is able to be determined through identifying (i) the antimicrobial-resistant clonal groups based on the fingerprints of the clone, (ii) the shift peak of the modified antimicrobial drug, which is inactivated by the resistance determinant, (iii) the shift peak of the modified antimicrobial target, (iv) the peak specific for the antimicrobial determinant, and (v) the biomarkers that are coproduced proteins with AMR determinants. This review aims to present the current usage of the MALDI-TOF MS technique for diagnosing antimicrobial resistance in bacteria, varied approaches for AMR diagnostics using the methodology, and the future applications of the methods for the accurate and rapid identification of AMR in infection-causing bacterial pathogens.
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Affiliation(s)
- Eun-Jeong Yoon
- Division of Antimicrobial Resistance, Center for Infectious Diseases, National Institute of Health, Korea Disease Control and Prevention Agency, Cheongju-si 28159, Korea;
- Department of Laboratory Medicine, Yonsei University College of Medicine, Seoul 06273, Korea
- Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul 06273, Korea
| | - Seok Hoon Jeong
- Department of Laboratory Medicine, Yonsei University College of Medicine, Seoul 06273, Korea
- Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul 06273, Korea
- Correspondence:
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43
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Song M, Liu Y, Li T, Liu X, Hao Z, Ding S, Panichayupakaranant P, Zhu K, Shen J. Plant Natural Flavonoids Against Multidrug Resistant Pathogens. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:e2100749. [PMID: 34041861 PMCID: PMC8336499 DOI: 10.1002/advs.202100749] [Citation(s) in RCA: 138] [Impact Index Per Article: 46.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 05/10/2021] [Indexed: 02/05/2023]
Abstract
The increasing emergence and dissemination of multidrug resistant (MDR) bacterial pathogens accelerate the desires for new antibiotics. Natural products dominate the preferred chemical scaffolds for the discovery of antibacterial agents. Here, the potential of natural flavonoids from plants against MDR bacteria, is demonstrated. Structure-activity relationship analysis shows the prenylation modulates the activity of flavonoids and obtains two compounds, α-mangostin (AMG) and isobavachalcone (IBC). AMG and IBC not only display rapid bactericidal activity against Gram-positive bacteria, but also restore the susceptibility of colistin against Gram-negative pathogens. Mechanistic studies generally show such compounds bind to the phospholipids of bacterial membrane, and result in the dissipation of proton motive force and metabolic perturbations, through distinctive modes of action. The efficacy of AMG and IBC in four models associated with infection or contamination, is demonstrated. These results suggest that natural products of plants may be a promising and underappreciated reservoir to circumvent the existing antibiotic resistance.
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Affiliation(s)
- Meirong Song
- National Center for Veterinary Drug Safety EvaluationCollege of Veterinary MedicineChina Agricultural UniversityBeijing100193China
| | - Ying Liu
- National Center for Veterinary Drug Safety EvaluationCollege of Veterinary MedicineChina Agricultural UniversityBeijing100193China
| | - Tingting Li
- National Center for Veterinary Drug Safety EvaluationCollege of Veterinary MedicineChina Agricultural UniversityBeijing100193China
| | - Xiaojia Liu
- National Center for Veterinary Drug Safety EvaluationCollege of Veterinary MedicineChina Agricultural UniversityBeijing100193China
| | - Zhihui Hao
- Center of Research and Innovation of Chinese Traditional Veterinary MedicineChina Agricultural UniversityBeijing100193China
| | - Shuangyang Ding
- Beijing Key Laboratory of Detection Technology for Animal‐Derived Food Safety and Beijing Laboratory for Food Quality and SafetyChina Agricultural UniversityBeijing100193China
| | - Pharkphoom Panichayupakaranant
- Department of Pharmacognosy and Pharmaceutical BotanyFaculty of Pharmaceutical SciencesPrince of Songkla UniversityHat‐Yai90112Thailand
| | - Kui Zhu
- National Center for Veterinary Drug Safety EvaluationCollege of Veterinary MedicineChina Agricultural UniversityBeijing100193China
- Center of Research and Innovation of Chinese Traditional Veterinary MedicineChina Agricultural UniversityBeijing100193China
| | - Jianzhong Shen
- National Center for Veterinary Drug Safety EvaluationCollege of Veterinary MedicineChina Agricultural UniversityBeijing100193China
- Beijing Key Laboratory of Detection Technology for Animal‐Derived Food Safety and Beijing Laboratory for Food Quality and SafetyChina Agricultural UniversityBeijing100193China
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44
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Liu J, Li H, Li H, Fang S, Shi J, Chen Y, Zhong R, Liu S, Lin S. Rational Design of Dipicolylamine-Containing Carbazole Amphiphiles Combined with Zn 2+ as Potent Broad-Spectrum Antibacterial Agents with a Membrane-Disruptive Mechanism. J Med Chem 2021; 64:10429-10444. [PMID: 34235929 DOI: 10.1021/acs.jmedchem.1c00858] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Antibiotic resistance has become one of the most urgently important problems facing healthcare providers. A novel series of dipicolylamine-containing carbazole amphiphiles with strong Zn2+ chelating ability were synthesized, biomimicking cationic antimicrobial peptides. Effective broad-spectrum 16 combined with 12.5 μg/mL Zn2+ was identified as the most promising antimicrobial candidate. 16 combined with 12.5 μg/mL Zn2+ exhibited excellent antimicrobial activity against both Gram-positive and Gram-negative bacteria (MICs = 0.78-3.125 μg/mL), weak hemolytic activity, and low cytotoxicity. Time-kill kinetics and mechanism studies revealed 16 combined with 12.5 μg/mL Zn2+ had rapid bacterial killing properties, as evidenced by disruption of the integrity of bacterial cell membranes, effectively preventing bacterial resistance development. Importantly, 16 combined with 12.5 μg/mL Zn2+ showed excellent in vivo efficacy in a murine keratitis model caused by Staphylococcus aureus ATCC29213 or Pseudomonas aeruginosa ATCC9027. Therefore, 16 combined with 12.5 μg/mL Zn2+ could be a promising candidate for treating bacterial infections.
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Affiliation(s)
- Jiayong Liu
- Key Laboratory of Molecular Target & Clinical Pharmacology and the State Key Laboratory of Respiratory Disease, School of Pharmaceutical Sciences & the Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou 511436, P.R. China
| | - Hongxia Li
- Key Laboratory of Molecular Target & Clinical Pharmacology and the State Key Laboratory of Respiratory Disease, School of Pharmaceutical Sciences & the Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou 511436, P.R. China
| | - Haizhou Li
- Key Laboratory of Molecular Target & Clinical Pharmacology and the State Key Laboratory of Respiratory Disease, School of Pharmaceutical Sciences & the Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou 511436, P.R. China
| | - Shanfang Fang
- Key Laboratory of Molecular Target & Clinical Pharmacology and the State Key Laboratory of Respiratory Disease, School of Pharmaceutical Sciences & the Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou 511436, P.R. China
| | - Jinguo Shi
- Department of Medicinal Chemistry, School of Pharmaceutical Science, Sun Yat-sen University, Guangzhou 510006, P. R. China
| | - Yongzhi Chen
- Key Laboratory of Molecular Target & Clinical Pharmacology and the State Key Laboratory of Respiratory Disease, School of Pharmaceutical Sciences & the Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou 511436, P.R. China
| | - Rongcui Zhong
- Key Laboratory of Molecular Target & Clinical Pharmacology and the State Key Laboratory of Respiratory Disease, School of Pharmaceutical Sciences & the Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou 511436, P.R. China
| | - Shouping Liu
- Key Laboratory of Molecular Target & Clinical Pharmacology and the State Key Laboratory of Respiratory Disease, School of Pharmaceutical Sciences & the Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou 511436, P.R. China
| | - Shuimu Lin
- Key Laboratory of Molecular Target & Clinical Pharmacology and the State Key Laboratory of Respiratory Disease, School of Pharmaceutical Sciences & the Fifth Affiliated Hospital, Guangzhou Medical University, Guangzhou 511436, P.R. China
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Harvey DJ. ANALYSIS OF CARBOHYDRATES AND GLYCOCONJUGATES BY MATRIX-ASSISTED LASER DESORPTION/IONIZATION MASS SPECTROMETRY: AN UPDATE FOR 2015-2016. MASS SPECTROMETRY REVIEWS 2021; 40:408-565. [PMID: 33725404 DOI: 10.1002/mas.21651] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 07/24/2020] [Indexed: 06/12/2023]
Abstract
This review is the ninth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2016. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation and arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals. Much of this material is presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented over 30 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show no sign of deminishing. © 2020 Wiley Periodicals, Inc.
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Affiliation(s)
- David J Harvey
- Nuffield Department of Medicine, Target Discovery Institute, University of Oxford, Roosevelt Drive, Oxford, OX3 7FZ, United Kingdom
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46
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Kazi MI, Perry BW, Card DC, Schargel RD, Ali HB, Obuekwe VC, Sapkota M, Kang KN, Pellegrino MW, Greenberg DE, Castoe TA, Boll JM. Discovery and characterization of New Delhi metallo-β-lactamase-1 inhibitor peptides that potentiate meropenem-dependent killing of carbapenemase-producing Enterobacteriaceae. J Antimicrob Chemother 2021; 75:2843-2851. [PMID: 32591801 DOI: 10.1093/jac/dkaa242] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 04/20/2020] [Accepted: 05/06/2020] [Indexed: 12/13/2022] Open
Abstract
OBJECTIVES Metallo-β-lactamases (MBLs) are an emerging class of antimicrobial resistance enzymes that degrade β-lactam antibiotics, including last-resort carbapenems. Infections caused by carbapenemase-producing Enterobacteriaceae (CPE) are increasingly prevalent, but treatment options are limited. While several serine-dependent β-lactamase inhibitors are formulated with commonly prescribed β-lactams, no MBL inhibitors are currently approved for combinatorial therapies. New compounds that target MBLs to restore carbapenem activity against CPE are therefore urgently needed. Herein we identified and characterized novel synthetic peptide inhibitors that bound to and inhibited NDM-1, which is an emerging β-lactam resistance mechanism in CPE. METHODS We leveraged Surface Localized Antimicrobial displaY (SLAY) to identify and characterize peptides that inhibit NDM-1, which is a primary carbapenem resistance mechanism in CPE. Lead inhibitor sequences were chemically synthesized and MBCs and MICs were calculated in the presence/absence of carbapenems. Kinetic analysis with recombinant NDM-1 and select peptides tested direct binding and supported NDM-1 inhibitor mechanisms of action. Inhibitors were also tested for cytotoxicity. RESULTS We identified approximately 1700 sequences that potentiated carbapenem-dependent killing against NDM-1 Escherichia coli. Several also enhanced meropenem-dependent killing of other CPE. Biochemical characterization of a subset indicated the peptides penetrated the bacterial periplasm and directly bound NDM-1 to inhibit enzymatic activity. Additionally, each demonstrated minimal haemolysis and cytotoxicity against mammalian cell lines. CONCLUSIONS Our approach advances a molecular platform for antimicrobial discovery, which complements the growing need for alternative antimicrobials. We also discovered lead NDM-1 inhibitors, which serve as a starting point for further chemical optimization.
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Affiliation(s)
- Misha I Kazi
- Department of Biology, University of Texas at Arlington, Arlington, TX, USA
| | - Blair W Perry
- Department of Biology, University of Texas at Arlington, Arlington, TX, USA
| | - Daren C Card
- Department of Biology, University of Texas at Arlington, Arlington, TX, USA
| | - Richard D Schargel
- Department of Biology, University of Texas at Arlington, Arlington, TX, USA
| | - Hana B Ali
- Department of Biology, University of Texas at Arlington, Arlington, TX, USA
| | - Victor C Obuekwe
- Department of Biology, University of Texas at Arlington, Arlington, TX, USA.,Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Madhab Sapkota
- Department of Biology, University of Texas at Arlington, Arlington, TX, USA
| | - Katie N Kang
- Department of Biology, University of Texas at Arlington, Arlington, TX, USA
| | - Mark W Pellegrino
- Department of Biology, University of Texas at Arlington, Arlington, TX, USA
| | - David E Greenberg
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Todd A Castoe
- Department of Biology, University of Texas at Arlington, Arlington, TX, USA
| | - Joseph M Boll
- Department of Biology, University of Texas at Arlington, Arlington, TX, USA
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Tao Y, Acket S, Beaumont E, Galez H, Duma L, Rossez Y. Colistin Treatment Affects Lipid Composition of Acinetobacter baumannii. Antibiotics (Basel) 2021; 10:antibiotics10050528. [PMID: 34063718 PMCID: PMC8147793 DOI: 10.3390/antibiotics10050528] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 04/30/2021] [Accepted: 05/01/2021] [Indexed: 12/15/2022] Open
Abstract
Multidrug-resistant Acinetobacter baumannii (A. baumannii) causes severe and often fatal healthcare-associated infections due partly to antibiotic resistance. There are no studies on A. baumannii lipidomics of susceptible and resistant strains grown at lethal and sublethal concentrations. Therefore, we analyzed the impact of colistin resistance on glycerolipids’ content by using untargeted lipidomics on clinical isolate. Nine lipid sub-classes were annotated, including phosphatidylcholine, rarely detected in the bacterial membrane among 130 different lipid species. The other lipid sub-classes detected are phosphatidylethanolamine (PE), phosphatidylglycerol (PG), lysophosphatidylethanolamine, hemibismonoacylglycerophosphate, cardiolipin, monolysocardiolipin, diacylglycerol, and triacylglycerol. Under lethal and sublethal concentrations of colistin, significant reduction of PE was observed on the resistant and susceptible strain, respectively. Palmitic acid percentage was higher at colistin at low concentration but only for the susceptible strain. When looking at individual lipid species, the most abundant PE and PG species (PE 34:1 and PG 34:1) are significantly upregulated when the susceptible and the resistant strains are cultivated with colistin. This is, to date, the most exhaustive lipidomics data compilation of A. baumannii cultivated in the presence of colistin. This work is highlighting the plasma membrane plasticity used by this gram-negative bacterium to survive colistin treatment.
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Acinetobacter baumannii LOS Regulate the Expression of Inflammatory Cytokine Genes and Proteins in Human Mast Cells. Pathogens 2021; 10:pathogens10030290. [PMID: 33802578 PMCID: PMC7998227 DOI: 10.3390/pathogens10030290] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 02/21/2021] [Accepted: 02/24/2021] [Indexed: 12/04/2022] Open
Abstract
Herein, we investigated the effect of bacterial lipooligosaccharides (LOS), from Acinetobacter baumannii, on the expression of pro-inflammatory genes that play an essential role in bacterial clearance. LAD2 human mast cells were stimulated with LOS derived from two strains of A. baumannii—ATCC 19606 and MDRA T14. LOS exposure induced the expression of genes for pro-inflammatory mediators, including TNF-α, IL-8, LTC4S, CCL4, and TLR4. The mRNA expression levels of a majority of the pro-inflammatory genes, except TLR4, in A. baumannii-LOS stimulated mast cells were increased. Moreover, co-culture of neutrophils with the supernatant obtained from LOS (ATCC 19606 and MDRA T14)-induced LAD2 cells increased the transmigration of neutrophils, which plays a critical role in the early protection against bacterial infections. The results of the present study suggest that LOS could be involved in the pathogenicity of A. baumannii by inducing inflammatory responses via mast cells and that IL-8 is involved in recruiting neutrophils in response to bacterial invasion.
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49
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Colistin Dependence in Extensively Drug-Resistant Acinetobacter baumannii Strain Is Associated with IS Ajo2 and IS Aba13 Insertions and Multiple Cellular Responses. Int J Mol Sci 2021; 22:ijms22020576. [PMID: 33430070 PMCID: PMC7827689 DOI: 10.3390/ijms22020576] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 01/05/2021] [Accepted: 01/06/2021] [Indexed: 02/06/2023] Open
Abstract
The nosocomial opportunistic Gram-negative bacterial pathogen Acinetobacter baumannii is resistant to multiple antimicrobial agents and an emerging global health problem. The polymyxin antibiotic colistin, targeting the negatively charged lipid A component of the lipopolysaccharide on the bacterial cell surface, is often considered as the last-resort treatment, but resistance to colistin is unfortunately increasing worldwide. Notably, colistin-susceptible A. baumannii can also develop a colistin dependence after exposure to this drug in vitro. Colistin dependence might represent a stepping stone to resistance also in vivo. However, the mechanisms are far from clear. To address this issue, we combined proteogenomics, high-resolution microscopy, and lipid profiling to characterize and compare A. baumannii colistin-susceptible clinical isolate (Ab-S) of to its colistin-dependent subpopulation (Ab-D) obtained after subsequent passages in moderate colistin concentrations. Incidentally, in the colistin-dependent subpopulation the lpxA gene was disrupted by insertion of ISAjo2, the lipid A biosynthesis terminated, and Ab-D cells displayed a lipooligosaccharide (LOS)-deficient phenotype. Moreover, both mlaD and pldA genes were perturbed by insertions of ISAjo2 and ISAba13, and LOS-deficient bacteria displayed a capsule with decreased thickness as well as other surface imperfections. The major changes in relative protein abundance levels were detected in type 6 secretion system (T6SS) components, the resistance-nodulation-division (RND)-type efflux pumps, and in proteins involved in maintenance of outer membrane asymmetry. These findings suggest that colistin dependence in A. baumannii involves an ensemble of mechanisms seen in resistance development and accompanied by complex cellular events related to insertional sequences (ISs)-triggered LOS-deficiency. To our knowledge, this is the first study demonstrating the involvement of ISAjo2 and ISAba13 IS elements in the modulation of the lipid A biosynthesis and associated development of dependence on colistin.
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Septal Class A Penicillin-Binding Protein Activity and ld-Transpeptidases Mediate Selection of Colistin-Resistant Lipooligosaccharide-Deficient Acinetobacter baumannii. mBio 2021; 12:mBio.02185-20. [PMID: 33402533 PMCID: PMC8545086 DOI: 10.1128/mbio.02185-20] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Despite dogma suggesting that lipopolysaccharide/lipooligosaccharide (LOS) was essential for viability of Gram-negative bacteria, several Acinetobacter baumannii clinical isolates produced LOS− colonies after colistin selection. Inactivation of the conserved class A penicillin-binding protein, PBP1A, was a compensatory mutation that supported isolation of LOS−A. baumannii, but the impact of PBP1A mutation was not characterized. Here, we show that the absence of PBP1A causes septation defects and that these, together with ld-transpeptidase activity, support isolation of LOS−A. baumannii. PBP1A contributes to proper cell division in A. baumannii, and its absence induced cell chaining. Only isolates producing three or more septa supported selection of colistin-resistant LOS−A. baumannii. PBP1A was enriched at the midcell, where the divisome complex facilitates daughter cell formation, and its localization was dependent on glycosyltransferase activity. Transposon mutagenesis showed that genes encoding two putative ld-transpeptidases (LdtJ and LdtK) became essential in the PBP1A mutant. Both LdtJ and LdtK were required for selection of LOS−A. baumannii, but each had distinct enzymatic activities in the cell. Together, these findings demonstrate that defects in PBP1A glycosyltransferase activity and ld-transpeptidase activity remodel the cell envelope to support selection of colistin-resistant LOS−A. baumannii.
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