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Ouyang Z, He W, Jiao M, Yu Q, Guo Y, Refat M, Qin Q, Zhang J, Shi Q, Zheng F, Wen Y. Mechanistic and biophysical characterization of polymyxin resistance response regulator PmrA in Acinetobacter baumannii. Front Microbiol 2024; 15:1293990. [PMID: 38476937 PMCID: PMC10927774 DOI: 10.3389/fmicb.2024.1293990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Accepted: 02/05/2024] [Indexed: 03/14/2024] Open
Abstract
Introduction Acinetobacter baumannii PmrAB is a crucial two-component regulatory system (TCS) that plays a vital role in conferring resistance to polymyxin. PmrA, a response regulator belonging to the OmpR/PhoB family, is composed of a C-terminal DNA-binding effector domain and an N-terminal receiver domain. The receiver domain can be phosphorylated by PmrB, a transmembrane sensor histidine kinase that interacts with PmrA. Once phosphorylated, PmrA undergoes a conformational change, resulting in the formation of a symmetric dimer in the receiver domain. This conformational change facilitates the recognition of promoter DNA by the DNA-binding domain of PmrA, leading to the activation of adaptive responses. Methods X-ray crystallography was carried out to solve the structure of PmrA receiver domain. Electrophoretic mobility shift assay and Isothermal titration calorimetry were recruited to validate the interaction between the recombinant PmrA protein and target DNA. Field-emission scanning electron microscopy (FE-SEM) was employed to characterize the surface morphology of A. baumannii in both the PmrA knockout and mutation strains. Results The receiver domain of PmrA follows the canonical α5β5 response regulator assembly, which undergoes dimerization upon phosphorylation and activation. Beryllium trifluoride is utilized as an aspartate phosphorylation mimic in this process. Mutations involved in phosphorylation and dimerization significantly affected the expression of downstream pmrC and naxD genes. This impact resulted in an enhanced cell surface smoothness with fewer modifications, ultimately contributing to a decrease in colistin (polymyxin E) and polymyxin B resistance. Additionally, a conservative direct-repeat DNA PmrA binding sequence TTTAAGNNNNNTTTAAG was identified at the promoter region of the pmrC and naxD gene. These findings provide structural insights into the PmrA receiver domain and reveal the mechanism of polymyxin resistance, suggesting that PmrA could be a potential drug target to reverse polymyxin resistance in Acinetobacter baumannii.
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Affiliation(s)
- Zhenlin Ouyang
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Wenbo He
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Min Jiao
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Qinyue Yu
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Yucheng Guo
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Moath Refat
- The Key Laboratory of Environment and Genes Related to Disease of Ministry of Education Health Science Center, Xi'an Jiaotong University, Xi'an, China
| | - Qian Qin
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Jiaxin Zhang
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Qindong Shi
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Fang Zheng
- The Key Laboratory of Environment and Genes Related to Disease of Ministry of Education Health Science Center, Xi'an Jiaotong University, Xi'an, China
| | - Yurong Wen
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
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Degabriel M, Valeva S, Boisset S, Henry T. Pathogenicity and virulence of Francisella tularensis. Virulence 2023; 14:2274638. [PMID: 37941380 PMCID: PMC10653695 DOI: 10.1080/21505594.2023.2274638] [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: 05/16/2023] [Accepted: 10/18/2023] [Indexed: 11/10/2023] Open
Abstract
Tularaemia is a zoonotic disease caused by the Gram-negative bacterium, Francisella tularensis. Depending on its entry route into the organism, F. tularensis causes different diseases, ranging from life-threatening pneumonia to less severe ulceroglandular tularaemia. Various strains with different geographical distributions exhibit different levels of virulence. F. tularensis is an intracellular bacterium that replicates primarily in the cytosol of the phagocytes. The main virulence attribute of F. tularensis is the type 6 secretion system (T6SS) and its effectors that promote escape from the phagosome. In addition, F. tularensis has evolved a peculiar envelope that allows it to escape detection by the immune system. In this review, we cover tularaemia, different Francisella strains, and their pathogenicity. We particularly emphasize the intracellular life cycle, associated virulence factors, and metabolic adaptations. Finally, we present how F. tularensis largely escapes immune detection to be one of the most infectious and lethal bacterial pathogens.
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Affiliation(s)
- Manon Degabriel
- CIRI, Centre International de Recherche en Infectiologie, Inserm U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de Lyon, Univ Lyon, LYON, France
| | - Stanimira Valeva
- CIRI, Centre International de Recherche en Infectiologie, Inserm U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de Lyon, Univ Lyon, LYON, France
| | - Sandrine Boisset
- CIRI, Centre International de Recherche en Infectiologie, Inserm U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de Lyon, Univ Lyon, LYON, France
- Univ. Grenoble Alpes, CHU Grenoble Alpes, CNRS, CEA, UMR5075, Institut de Biologie Structurale, Grenoble, France
| | - Thomas Henry
- CIRI, Centre International de Recherche en Infectiologie, Inserm U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de Lyon, Univ Lyon, LYON, France
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Thai VC, Stubbs KA, Sarkar-Tyson M, Kahler CM. Phosphoethanolamine Transferases as Drug Discovery Targets for Therapeutic Treatment of Multi-Drug Resistant Pathogenic Gram-Negative Bacteria. Antibiotics (Basel) 2023; 12:1382. [PMID: 37760679 PMCID: PMC10525099 DOI: 10.3390/antibiotics12091382] [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: 08/04/2023] [Revised: 08/25/2023] [Accepted: 08/26/2023] [Indexed: 09/29/2023] Open
Abstract
Antibiotic resistance caused by multidrug-resistant (MDR) bacteria is a major challenge to global public health. Polymyxins are increasingly being used as last-in-line antibiotics to treat MDR Gram-negative bacterial infections, but resistance development renders them ineffective for empirical therapy. The main mechanism that bacteria use to defend against polymyxins is to modify the lipid A headgroups of the outer membrane by adding phosphoethanolamine (PEA) moieties. In addition to lipid A modifying PEA transferases, Gram-negative bacteria possess PEA transferases that decorate proteins and glycans. This review provides a comprehensive overview of the function, structure, and mechanism of action of PEA transferases identified in pathogenic Gram-negative bacteria. It also summarizes the current drug development progress targeting this enzyme family, which could reverse antibiotic resistance to polymyxins to restore their utility in empiric therapy.
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Affiliation(s)
- Van C. Thai
- The Marshall Center for Infectious Diseases Research and Training, School of Biomedical Sciences, University of Western Australia, Crawley, WA 6009, Australia; (V.C.T.); (M.S.-T.)
| | - Keith A. Stubbs
- School of Molecular Sciences, University of Western Australia, Crawley, WA 6009, Australia;
| | - Mitali Sarkar-Tyson
- The Marshall Center for Infectious Diseases Research and Training, School of Biomedical Sciences, University of Western Australia, Crawley, WA 6009, Australia; (V.C.T.); (M.S.-T.)
| | - Charlene M. Kahler
- The Marshall Center for Infectious Diseases Research and Training, School of Biomedical Sciences, University of Western Australia, Crawley, WA 6009, Australia; (V.C.T.); (M.S.-T.)
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Cavallo I, Oliva A, Pages R, Sivori F, Truglio M, Fabrizio G, Pasqua M, Pimpinelli F, Di Domenico EG. Acinetobacter baumannii in the critically ill: complex infections get complicated. Front Microbiol 2023; 14:1196774. [PMID: 37425994 PMCID: PMC10325864 DOI: 10.3389/fmicb.2023.1196774] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 06/05/2023] [Indexed: 07/11/2023] Open
Abstract
Acinetobacter baumannii is increasingly associated with various epidemics, representing a serious concern due to the broad level of antimicrobial resistance and clinical manifestations. During the last decades, A. baumannii has emerged as a major pathogen in vulnerable and critically ill patients. Bacteremia, pneumonia, urinary tract, and skin and soft tissue infections are the most common presentations of A. baumannii, with attributable mortality rates approaching 35%. Carbapenems have been considered the first choice to treat A. baumannii infections. However, due to the widespread prevalence of carbapenem-resistant A. baumannii (CRAB), colistin represents the main therapeutic option, while the role of the new siderophore cephalosporin cefiderocol still needs to be ascertained. Furthermore, high clinical failure rates have been reported for colistin monotherapy when used to treat CRAB infections. Thus, the most effective antibiotic combination remains disputed. In addition to its ability to develop antibiotic resistance, A. baumannii is also known to form biofilm on medical devices, including central venous catheters or endotracheal tubes. Thus, the worrisome spread of biofilm-producing strains in multidrug-resistant populations of A. baumannii poses a significant treatment challenge. This review provides an updated account of antimicrobial resistance patterns and biofilm-mediated tolerance in A. baumannii infections with a special focus on fragile and critically ill patients.
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Affiliation(s)
- Ilaria Cavallo
- Microbiology and Virology, San Gallicano Dermatological Institute, IRCCS, Rome, Italy
| | - Alessandra Oliva
- Department of Public Health and Infectious Diseases, Sapienza University of Rome, Rome, Italy
| | - Rebecca Pages
- Microbiology and Virology, San Gallicano Dermatological Institute, IRCCS, Rome, Italy
| | - Francesca Sivori
- Microbiology and Virology, San Gallicano Dermatological Institute, IRCCS, Rome, Italy
| | - Mauro Truglio
- Microbiology and Virology, San Gallicano Dermatological Institute, IRCCS, Rome, Italy
| | - Giorgia Fabrizio
- Microbiology and Virology, San Gallicano Dermatological Institute, IRCCS, Rome, Italy
| | - Martina Pasqua
- Department of Biology and Biotechnology "C. Darwin" Sapienza University of Rome, Rome, Italy
| | - Fulvia Pimpinelli
- Microbiology and Virology, San Gallicano Dermatological Institute, IRCCS, Rome, Italy
| | - Enea Gino Di Domenico
- Department of Biology and Biotechnology "C. Darwin" Sapienza University of Rome, Rome, Italy
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Panda G, Dash S, Sahu SK. Harnessing the Role of Bacterial Plasma Membrane Modifications for the Development of Sustainable Membranotropic Phytotherapeutics. MEMBRANES 2022; 12:914. [PMID: 36295673 PMCID: PMC9612325 DOI: 10.3390/membranes12100914] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Revised: 09/08/2022] [Accepted: 09/19/2022] [Indexed: 06/16/2023]
Abstract
Membrane-targeted molecules such as cationic antimicrobial peptides (CAMPs) are amongst the most advanced group of antibiotics used against drug-resistant bacteria due to their conserved and accessible targets. However, multi-drug-resistant bacteria alter their plasma membrane (PM) lipids, such as lipopolysaccharides (LPS) and phospholipids (PLs), to evade membrane-targeted antibiotics. Investigations reveal that in addition to LPS, the varying composition and spatiotemporal organization of PLs in the bacterial PM are currently being explored as novel drug targets. Additionally, PM proteins such as Mla complex, MPRF, Lpts, lipid II flippase, PL synthases, and PL flippases that maintain PM integrity are the most sought-after targets for development of new-generation drugs. However, most of their structural details and mechanism of action remains elusive. Exploration of the role of bacterial membrane lipidome and proteome in addition to their organization is the key to developing novel membrane-targeted antibiotics. In addition, membranotropic phytochemicals and their synthetic derivatives have gained attractiveness as popular herbal alternatives against bacterial multi-drug resistance. This review provides the current understanding on the role of bacterial PM components on multidrug resistance and their targeting with membranotropic phytochemicals.
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Affiliation(s)
- Gayatree Panda
- Department of Biotechnology, Maharaja Sriram Chandra Bhanjadeo University (Erstwhile: North Orissa University), Baripada 757003, India
| | - Sabyasachi Dash
- Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY 10065, USA
| | - Santosh Kumar Sahu
- Department of Biotechnology, Maharaja Sriram Chandra Bhanjadeo University (Erstwhile: North Orissa University), Baripada 757003, India
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Constitutive Phenotypic Modification of Lipid A in Clinical Acinetobacter baumannii Isolates. Microbiol Spectr 2022; 10:e0129522. [PMID: 35861511 PMCID: PMC9431647 DOI: 10.1128/spectrum.01295-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
The degree of polymyxin B (PMB) resistance was measured in 40 clinical Acinetobacter baumannii isolates obtained from health care facilities. All of the tested isolates possessed a multidrug-resistant (MDR) phenotype against four classes of antibiotics (meropenem, doxycycline, gentamicin, and erythromycin), except for PMB. The blaOXA-23 gene was detected throughout the genetic analysis and experimental assay, indicating that all of the MDR strains were carbapenem-resistant A. baumannii strains. Multilocus sequence typing-based genotyping revealed that nine selected strains belonged to the international clone II lineage. When matrix-assisted laser desorption ionization–time of flight mass spectrometry was performed, intrinsic lipid A modification by phosphoethanolamine (PEtN) incorporation was noticeable only in the PMB-resistant (PMBR) strains. However, the presence of hexa- and penta-acylated lipid A due to the loss of the laurate (C12) acyl chain was noted in all PMB-susceptible strains but not in the PMBR strains. The reduction of negative surface charges in the PMBR strains was assessed by zeta potential analysis. Fluorescence imaging using dansyl-PMB revealed that, in the PMBR strains, PMB was less likely to bind to the cell surface. IMPORTANCE The widespread presence of MDR pathogens, including A. baumannii, is causing serious hospital-acquired infections worldwide. Extensive surveillance of MDR clinical A. baumannii isolates has been conducted, but the underlying mechanisms for their development of MDR phenotypes are often neglected. Either lipid A modification or loss of lipopolysaccharide in Gram-negative bacteria leads to PMBR phenotypes. The prevalence of intrinsic lipid A modification in PMBR clinical strains was attributed to high levels of basal expression of pmrC and eptA-1. Our findings suggest that new therapeutic strategies are warranted to combat MDR pathogens due to the emergence of many PMBR clinical strains.
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Zhang S, Abbas M, Rehman MU, Wang M, Jia R, Chen S, Liu M, Zhu D, Zhao X, Gao Q, Tian B, Cheng A. Updates on the global dissemination of colistin-resistant Escherichia coli: An emerging threat to public health. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 799:149280. [PMID: 34364270 DOI: 10.1016/j.scitotenv.2021.149280] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 07/22/2021] [Accepted: 07/22/2021] [Indexed: 06/13/2023]
Abstract
Colistin drug resistance is an emerging public health threat worldwide. The adaptability, existence and spread of colistin drug resistance in multiple reservoirs and ecological environmental settings is significantly increasing the rate of occurrence of multidrug resistant (MDR) bacteria such as Escherichia coli (E. coli). Here, we summarized the reports regarding molecular and biological characterization of mobile colistin resistance gene (mcr)-positive E. coli (MCRPEC), originating from diverse reservoirs, including but not limited to humans, environment, waste water treatment plants, wild, pets, and food producing animals. The MCRPEC revealed the abundance of clinically important resistance genes, which are responsible for MDR profile. A number of plasmid replicon types such as IncI2, IncX4, IncP, IncX, and IncFII with a predominance of IncI2 were facilitating the spread of colistin resistance. This study concludes the distribution of multiple sequence types of E. coli carrying mcr gene variants, which are possible threat to "One Health" perspective. In addition, we have briefly explained the newly known mechanisms of colistin resistance i.e. plasmid-encoded resistance determinant as well as presented the chromosomally-encoded resistance mechanisms. The transposition of ISApl1 into the chromosome and existence of intact Tn6330 are important for transmission and stability for mcr gene. Further, genetic environment of co-localized mcr gene with carbapenem-resistance or extended-spectrum β-lactamases genes has also been elaborated, which is limiting human beings to choose last resort antibiotics. Finally, environmental health and safety control measures along with spread mechanisms of mcr genes are discussed to avoid further propagation and environmental hazards of colistin resistance.
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Affiliation(s)
- Shaqiu Zhang
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, PR China
| | - Muhammad Abbas
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, PR China; Livestock and Dairy Development Department Lahore, Punjab 54000, Pakistan
| | - Mujeeb Ur Rehman
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, PR China; Disease Investigation Laboratory, Livestock & Dairy Development Department, Zhob 85200, Balochistan, Pakistan
| | - Mingshu Wang
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, PR China
| | - Renyong Jia
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, PR China
| | - Shun Chen
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, PR China
| | - Mafeng Liu
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, PR China
| | - Dekang Zhu
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, PR China
| | - Xinxin Zhao
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, PR China
| | - Qun Gao
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, PR China
| | - Bin Tian
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, PR China
| | - Anchun Cheng
- Avian Disease Research Center, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu 611130, PR China; Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, PR China.
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Chin CY, Zhao J, Llewellyn AC, Golovliov I, Sjöstedt A, Zhou P, Weiss DS. Francisella FlmX broadly affects lipopolysaccharide modification and virulence. Cell Rep 2021; 35:109247. [PMID: 34133919 DOI: 10.1016/j.celrep.2021.109247] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 01/14/2021] [Accepted: 05/20/2021] [Indexed: 10/21/2022] Open
Abstract
The outer membrane protects Gram-negative bacteria from the host environment. Lipopolysaccharide (LPS), a major outer membrane constituent, has distinct components (lipid A, core, O-antigen) generated by specialized pathways. In this study, we describe the surprising convergence of these pathways through FlmX, an uncharacterized protein in the intracellular pathogen Francisella. FlmX is in the flippase family, which includes proteins that traffic lipid-linked envelope components across membranes. flmX deficiency causes defects in lipid A modification, core remodeling, and O-antigen addition. We find that an F. tularensis mutant lacking flmX is >1,000,000-fold attenuated. Furthermore, FlmX is required to resist the innate antimicrobial LL-37 and the antibiotic polymyxin. Given FlmX's central role in LPS modification and its conservation in intracellular pathogens Brucella, Coxiella, and Legionella, FlmX may represent a novel drug target whose inhibition could cripple bacterial virulence and sensitize bacteria to innate antimicrobials and antibiotics.
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Affiliation(s)
- Chui-Yoke Chin
- Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, GA 30329, USA; Emory Vaccine Center, Emory University School of Medicine, Atlanta, GA 30329, USA; Yerkes National Primate Research Center, Emory University School of Medicine, Atlanta, GA 30329, USA; Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30329, USA
| | - Jinshi Zhao
- Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA
| | - Anna C Llewellyn
- Emory Vaccine Center, Emory University School of Medicine, Atlanta, GA 30329, USA; Yerkes National Primate Research Center, Emory University School of Medicine, Atlanta, GA 30329, USA; Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30329, USA
| | - Igor Golovliov
- Clinical Bacteriology, and Laboratory for Molecular Infection Medicine Sweden, Department of Clinical Microbiology, Umeå University, 90185 Umeå, Sweden
| | - Anders Sjöstedt
- Clinical Bacteriology, and Laboratory for Molecular Infection Medicine Sweden, Department of Clinical Microbiology, Umeå University, 90185 Umeå, Sweden
| | - Pei Zhou
- Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA
| | - David S Weiss
- Emory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, GA 30329, USA; Emory Vaccine Center, Emory University School of Medicine, Atlanta, GA 30329, USA; Yerkes National Primate Research Center, Emory University School of Medicine, Atlanta, GA 30329, USA; Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30329, USA; Research Service, Atlanta VA Medical Center, Decatur, GA 30033, USA.
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Kassinger SJ, van Hoek ML. Genetic Determinants of Antibiotic Resistance in Francisella. Front Microbiol 2021; 12:644855. [PMID: 34054749 PMCID: PMC8149597 DOI: 10.3389/fmicb.2021.644855] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 03/25/2021] [Indexed: 12/21/2022] Open
Abstract
Tularemia, caused by Francisella tularensis, is endemic to the northern hemisphere. This zoonotic organism has historically been developed into a biological weapon. For this Tier 1, Category A select agent, it is important to expand our understanding of its mechanisms of antibiotic resistance (AMR). Francisella is unlike many Gram-negative organisms in that it does not have significant plasmid mobility, and does not express AMR mechanisms on plasmids; thus plasmid-mediated resistance does not occur naturally. It is possible to artificially introduce plasmids with AMR markers for cloning and gene expression purposes. In this review, we survey both the experimental research on AMR in Francisella and bioinformatic databases which contain genomic and proteomic data. We explore both the genetic determinants of intrinsic AMR and naturally acquired or engineered antimicrobial resistance as well as phenotypic resistance in Francisella. Herein we survey resistance to beta-lactams, monobactams, carbapenems, aminoglycosides, tetracycline, polymyxins, macrolides, rifampin, fosmidomycin, and fluoroquinolones. We also highlight research about the phenotypic AMR difference between planktonic and biofilm Francisella. We discuss newly developed methods of testing antibiotics against Francisella which involve the intracellular nature of Francisella infection and may better reflect the eventual clinical outcomes for new antibiotic compounds. Understanding the genetically encoded determinants of AMR in Francisella is key to optimizing the treatment of patients and potentially developing new antimicrobials for this dangerous intracellular pathogen.
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Affiliation(s)
| | - Monique L. van Hoek
- School of Systems Biology, George Mason University, Manassas, VA, United States
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Cardoso P, Glossop H, Meikle TG, Aburto-Medina A, Conn CE, Sarojini V, Valery C. Molecular engineering of antimicrobial peptides: microbial targets, peptide motifs and translation opportunities. Biophys Rev 2021; 13:35-69. [PMID: 33495702 PMCID: PMC7817352 DOI: 10.1007/s12551-021-00784-y] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Accepted: 01/07/2021] [Indexed: 02/07/2023] Open
Abstract
The global public health threat of antimicrobial resistance has led the scientific community to highly engage into research on alternative strategies to the traditional small molecule therapeutics. Here, we review one of the most popular alternatives amongst basic and applied research scientists, synthetic antimicrobial peptides. The ease of peptide chemical synthesis combined with emerging engineering principles and potent broad-spectrum activity, including against multidrug-resistant strains, has motivated intense scientific focus on these compounds for the past decade. This global effort has resulted in significant advances in our understanding of peptide antimicrobial activity at the molecular scale. Recent evidence of molecular targets other than the microbial lipid membrane, and efforts towards consensus antimicrobial peptide motifs, have supported the rise of molecular engineering approaches and design tools, including machine learning. Beyond molecular concepts, supramolecular chemistry has been lately added to the debate; and helped unravel the impact of peptide self-assembly on activity, including on biofilms and secondary targets, while providing new directions in pharmaceutical formulation through taking advantage of peptide self-assembled nanostructures. We argue that these basic research advances constitute a solid basis for promising industry translation of rationally designed synthetic peptide antimicrobials, not only as novel drugs against multidrug-resistant strains but also as components of emerging antimicrobial biomaterials. This perspective is supported by recent developments of innovative peptide-based and peptide-carrier nanobiomaterials that we also review.
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Affiliation(s)
- Priscila Cardoso
- School of Health and Biomedical Sciences, RMIT University, Melbourne, Australia.,School of Science, RMIT University, Melbourne, Australia
| | - Hugh Glossop
- School of Chemical Sciences, University of Auckland, Auckland, New Zealand
| | | | | | | | | | - Celine Valery
- School of Health and Biomedical Sciences, RMIT University, Melbourne, Australia
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11
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12
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Inhibition of Francisella tularensis phagocytosis using a novel anti-LPS scFv antibody fragment. Sci Rep 2019; 9:11418. [PMID: 31388083 PMCID: PMC6684794 DOI: 10.1038/s41598-019-47931-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 07/25/2019] [Indexed: 12/23/2022] Open
Abstract
Francisella tularensis (Ft), the causative agent of lethal tularemia, is classified as a category A biological warfare threat agent. While Ft infection is treatable by antibiotics, many failed antibiotic treatments were reported, highlighting the need for effective new treatments. It has been demonstrated that binding of antibody-coated bacteria to the Fc receptor located on phagocytic cells is a key process needed for efficient protection against Ft. Yet, Ft utilizes the same receptor to enter the phagocytic cells in order to escape the immune system. To address the question whether an anti-Ft LPS antibody lacking the ability to bind the Fc receptor may inhibit the entry of Ft into host cells, a soluble scFv (TL1-scFv) was constructed from an anti Ft-LPS antibody (TL1) that was isolated from an immune single-chain (scFv) phage-display library. Bacterial uptake was assessed upon infection of macrophages with Ft live attenuated strain (LVS) in the presence of either TL1 or TL1-scFv. While incubation of LVS in the presence of TL1 greatly enhanced bacterial uptake, LVS uptake was significantly inhibited in the presence of TL1-scFv. These results prompt further experiments probing the therapeutic efficacy of TL1-scFv, alone or in combination with antibiotic treatment.
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13
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Ratner HK, Escalera-Maurer A, Le Rhun A, Jaggavarapu S, Wozniak JE, Crispell EK, Charpentier E, Weiss DS. Catalytically Active Cas9 Mediates Transcriptional Interference to Facilitate Bacterial Virulence. Mol Cell 2019; 75:498-510.e5. [PMID: 31256988 DOI: 10.1016/j.molcel.2019.05.029] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 01/14/2019] [Accepted: 05/21/2019] [Indexed: 12/26/2022]
Abstract
In addition to defense against foreign DNA, the CRISPR-Cas9 system of Francisella novicida represses expression of an endogenous immunostimulatory lipoprotein. We investigated the specificity and molecular mechanism of this regulation, demonstrating that Cas9 controls a highly specific regulon of four genes that must be repressed for bacterial virulence. Regulation occurs through a protospacer adjacent motif (PAM)-dependent interaction of Cas9 with its endogenous DNA targets, dependent on a non-canonical small RNA (scaRNA) and tracrRNA. The limited complementarity between scaRNA and the endogenous DNA targets precludes cleavage, highlighting the evolution of scaRNA to repress transcription without lethally targeting the chromosome. We show that scaRNA can be reprogrammed to repress other genes, and with engineered, extended complementarity to an exogenous target, the repurposed scaRNA:tracrRNA-FnoCas9 machinery can also direct DNA cleavage. Natural Cas9 transcriptional interference likely represents a broad paradigm of regulatory functionality, which is potentially critical to the physiology of numerous Cas9-encoding pathogenic and commensal organisms.
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Affiliation(s)
- Hannah K Ratner
- Microbiology and Molecular Genetics Program, Emory University, Atlanta, GA 30329, USA; Emory Vaccine Center, Emory University, Atlanta, GA 30329, USA; Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
| | - Andrés Escalera-Maurer
- Max Planck Unit for the Science of Pathogens, 10117 Berlin, Germany; Helmholtz Centre for Infection Research, Department of Regulation in Infection Biology, 38124 Braunschweig, Germany; Institute for Biology, Humboldt University, 10115 Berlin, Germany
| | - Anaïs Le Rhun
- Max Planck Unit for the Science of Pathogens, 10117 Berlin, Germany; Helmholtz Centre for Infection Research, Department of Regulation in Infection Biology, 38124 Braunschweig, Germany
| | - Siddharth Jaggavarapu
- Emory Vaccine Center, Emory University, Atlanta, GA 30329, USA; Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA; Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30329, USA
| | - Jessie E Wozniak
- Microbiology and Molecular Genetics Program, Emory University, Atlanta, GA 30329, USA; Emory Vaccine Center, Emory University, Atlanta, GA 30329, USA; Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
| | - Emily K Crispell
- Microbiology and Molecular Genetics Program, Emory University, Atlanta, GA 30329, USA; Emory Vaccine Center, Emory University, Atlanta, GA 30329, USA; Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
| | - Emmanuelle Charpentier
- Max Planck Unit for the Science of Pathogens, 10117 Berlin, Germany; Helmholtz Centre for Infection Research, Department of Regulation in Infection Biology, 38124 Braunschweig, Germany; Institute for Biology, Humboldt University, 10115 Berlin, Germany
| | - David S Weiss
- Microbiology and Molecular Genetics Program, Emory University, Atlanta, GA 30329, USA; Emory Vaccine Center, Emory University, Atlanta, GA 30329, USA; Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA; Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30329, USA.
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14
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Wang Q, Sun J, Li J, Ding Y, Li XP, Lin J, Hassan B, Feng Y. Expanding landscapes of the diversified mcr-1-bearing plasmid reservoirs. MICROBIOME 2017; 5:70. [PMID: 28683827 PMCID: PMC5500976 DOI: 10.1186/s40168-017-0288-0] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 06/19/2017] [Indexed: 06/07/2023]
Abstract
BACKGROUND Polymyxin is a cationic polypeptide antibiotic that can disrupt bacterial cell membrane by interacting with its lipopolysaccharide molecules and is used as a last resort drug against lethal infections by the carbapenem-resistant superbugs (like NDM-1). However, global discovery of the MCR-1 colistin resistance dramatically challenges the newly renewed interest in colistin for clinical use. METHODS The mcr-1-harboring plasmids were acquired from swine and human Escherichia coli isolated in China, from 2015 to 2016, and subjected to Illumina PacBio RSII and Hi-Seq2000 for full genome sequencing. PCR was applied to close the gap of the assembled contigs. Ori-Finder was employed to predict the replication origin (oriC) in plasmids. The phenotype of MCR-1-producing isolates was evaluated on the LBA plates with various level of colistin. Genetic deletion was used to test the requirement of the initial "ATG" codon for the MCR-1 function. RESULTS Here, we report full genomes of over 10 mcr-1-harboring plasmids with diversified replication incompatibilities. A novel hybrid IncI2/IncFIB plasmid pGD17-2 was discovered and characterized from a swine isolate with colistin resistance. Intriguingly, co-occurrence of two unique mcr-1-bearing plasmids (pGD65-3, IncI2, and pGD65-5, IncX4) was detected in a single isolate GD65, which might accelerate dissemination of the mcr-1 under environmental selection pressure. Genetic analyses of these plasmids mapped mobile elements in the context of antibiotic resistance and determined two insertion sequences (ISEcp1 and ISApl1) that are responsible for the mobilization of mcr-1. Gene deletion also proved that the first ATG codon is redundant in the mcr-1 gene. CONCLUSIONS Collectively, our results extend landscapes of the diversified mcr-1-bearing plasmid reservoirs.
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Affiliation(s)
- Qingjing Wang
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, 310058, Zhejiang, China
| | - Jian Sun
- National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, Guangdong, China
| | - Jun Li
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, 310014, Zhejiang, China
| | - Youfa Ding
- Lishui People's Hospital, Lishui, 323000, Zhejiang, China
| | - Xing-Ping Li
- National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, Guangdong, China
| | - Jingxia Lin
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, 310058, Zhejiang, China
| | | | - Youjun Feng
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, 310058, Zhejiang, China.
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15
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Cardoso MH, de Almeida KC, Cândido EDS, Murad AM, Dias SC, Franco OL. Comparative NanoUPLC-MS E analysis between magainin I-susceptible and -resistant Escherichia coli strains. Sci Rep 2017. [PMID: 28646205 PMCID: PMC5482854 DOI: 10.1038/s41598-017-04181-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In recent years the antimicrobial peptides (AMPs) have been prospected and designed as new alternatives to conventional antibiotics. Indeed, AMPs have presented great potential toward pathogenic bacterial strains by means of complex mechanisms of action. However, reports have increasingly emerged regarding the mechanisms by which bacteria resist AMP administration. In this context, we performed a comparative proteomic study by using the total bacterial lysate of magainin I-susceptible and –resistant E. coli strains. After nanoUPLC-MSE analyses we identified 742 proteins distributed among the experimental groups, and 25 proteins were differentially expressed in the resistant strains. Among them 10 proteins involved in bacterial resistance, homeostasis, nutrition and protein transport were upregulated, while 15 proteins related to bacterial surface modifications, genetic information and β-lactams binding-protein were downregulated. Moreover, 60 exclusive proteins were identified in the resistant strains, among which biofilm and cell wall formation and multidrug efflux pump proteins could be observed. Thus, differentially from previous studies that could only associate single proteins to AMP bacterial resistance, data here reported show that several metabolic pathways may be related to E. coli resistance to AMPs, revealing the crucial role of multiple “omics” studies in order to elucidate the global molecular mechanisms involved in this resistance.
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Affiliation(s)
- Marlon H Cardoso
- Centro de Análises Proteômicas e Bioquímicas, Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, Brasília-DF, 70.790-160, Brazil.,Programa de Pós-Graduação em Patologia Molecular, Faculdade de Medicina, Universidade de Brasília, Brasília-DF, 70.910-900, Brazil.,S-Inova Biotech, Pós-graduação em Biotecnologia, Universidade Católica Dom Bosco, Campo Grande-MS, 79.117-900, Brazil
| | - Keyla C de Almeida
- Centro de Análises Proteômicas e Bioquímicas, Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, Brasília-DF, 70.790-160, Brazil.,Programa de Pós-Graduação em Patologia Molecular, Faculdade de Medicina, Universidade de Brasília, Brasília-DF, 70.910-900, Brazil
| | - Elizabete de S Cândido
- Centro de Análises Proteômicas e Bioquímicas, Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, Brasília-DF, 70.790-160, Brazil.,S-Inova Biotech, Pós-graduação em Biotecnologia, Universidade Católica Dom Bosco, Campo Grande-MS, 79.117-900, Brazil
| | - André M Murad
- Embrapa Recursos Genéticos e Biotecnologia, Laboratório de Biologia Sintética, Parque Estação Biológica, Brasília-DF, 70.770-917, Brazil
| | - Simoni C Dias
- Centro de Análises Proteômicas e Bioquímicas, Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, Brasília-DF, 70.790-160, Brazil
| | - Octávio L Franco
- Centro de Análises Proteômicas e Bioquímicas, Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, Brasília-DF, 70.790-160, Brazil. .,Programa de Pós-Graduação em Patologia Molecular, Faculdade de Medicina, Universidade de Brasília, Brasília-DF, 70.910-900, Brazil. .,S-Inova Biotech, Pós-graduação em Biotecnologia, Universidade Católica Dom Bosco, Campo Grande-MS, 79.117-900, Brazil.
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16
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Cheng Q, Wu L, Tu R, Wu J, Kang W, Su T, Du R, Liu W. Mycoplasma fermentans deacetylase promotes mammalian cell stress tolerance. Microbiol Res 2017; 201:1-11. [PMID: 28602396 DOI: 10.1016/j.micres.2017.04.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Revised: 04/09/2017] [Accepted: 04/22/2017] [Indexed: 12/19/2022]
Abstract
Mycoplasma fermentans is a pathogenic bacterium that infects humans and has potential pathogenic roles in respiratory, genital and rheumatoid diseases. NAD+-dependent deacetylase is involved in a wide range of pathophysiological processes and our studies have demonstrated that expression of mycoplasmal deacetylase in mammalian cells inhibits proliferation but promotes anti-starvation stress tolerance. Furthermore, mycoplasmal deacetylase is involved in cellular anti-oxidation, which correlates with changes in the proapoptotic proteins BIK, p21 and BIM. Mycoplasmal deacetylase binds to and deacetylates the FOXO3 protein, similar with mammalian SIRT2, and affects expression of the FOXO3 target gene BIM, resulting in inhibition of cell proliferation. Mycoplasmal deacetylase also alters the performance of cells under drug stress. This study expands our understanding of the potential molecular and cellular mechanisms of interaction between mycoplasmas and mammalian cells.
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Affiliation(s)
- Qingzhou Cheng
- College of Health Sciences and Nursing, Wuhan Polytechnic University, Wuhan, Hubei, China
| | - Lijuan Wu
- College of Health Sciences and Nursing, Wuhan Polytechnic University, Wuhan, Hubei, China
| | - Rongfu Tu
- College of Life Sciences, Wuhan University, Wuhan, Hubei, China
| | - Jun Wu
- College of Health Sciences and Nursing, Wuhan Polytechnic University, Wuhan, Hubei, China
| | - Wenqian Kang
- College of Life Sciences, Wuhan University, Wuhan, Hubei, China
| | - Tong Su
- College of Life Sciences, Wuhan University, Wuhan, Hubei, China
| | - Runlei Du
- College of Life Sciences, Wuhan University, Wuhan, Hubei, China.
| | - Wenbin Liu
- College of Health Sciences and Nursing, Wuhan Polytechnic University, Wuhan, Hubei, China; College of Medicine, University of Florida, Gainesville, FL, USA.
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17
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A spontaneous mutation in kdsD, a biosynthesis gene for 3 Deoxy-D-manno-Octulosonic Acid, occurred in a ciprofloxacin resistant strain of Francisella tularensis and caused a high level of attenuation in murine models of tularemia. PLoS One 2017; 12:e0174106. [PMID: 28328947 PMCID: PMC5362203 DOI: 10.1371/journal.pone.0174106] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 03/03/2017] [Indexed: 12/26/2022] Open
Abstract
Francisella tularensis, a gram-negative facultative intracellular bacterial pathogen, is the causative agent of tularemia and able to infect many mammalian species, including humans. Because of its ability to cause a lethal infection, low infectious dose, and aerosolizable nature, F. tularensis subspecies tularensis is considered a potential biowarfare agent. Due to its in vitro efficacy, ciprofloxacin is one of the antibiotics recommended for post-exposure prophylaxis of tularemia. In order to identify therapeutics that will be efficacious against infections caused by drug resistant select-agents and to better understand the threat, we sought to characterize an existing ciprofloxacin resistant (CipR) mutant in the Schu S4 strain of F. tularensis by determining its phenotypic characteristics and sequencing the chromosome to identify additional genetic alterations that may have occurred during the selection process. In addition to the previously described genetic alterations, the sequence of the CipR mutant strain revealed several additional mutations. Of particular interest was a frameshift mutation within kdsD which encodes for an enzyme necessary for the production of 3-Deoxy-D-manno-Octulosonic Acid (KDO), an integral component of the lipopolysaccharide (LPS). A kdsD mutant was constructed in the Schu S4 strain. Although it was not resistant to ciprofloxacin, the kdsD mutant shared many phenotypic characteristics with the CipR mutant, including growth defects under different conditions, sensitivity to hydrophobic agents, altered LPS profiles, and attenuation in multiple models of murine tularemia. This study demonstrates that the KdsD enzyme is essential for Francisella virulence and may be an attractive therapeutic target for developing novel medical countermeasures.
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18
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Trimble MJ, Mlynárčik P, Kolář M, Hancock REW. Polymyxin: Alternative Mechanisms of Action and Resistance. Cold Spring Harb Perspect Med 2016; 6:cshperspect.a025288. [PMID: 27503996 DOI: 10.1101/cshperspect.a025288] [Citation(s) in RCA: 243] [Impact Index Per Article: 30.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Antibiotic resistance among pathogenic bacteria is an ever-increasing issue worldwide. Unfortunately, very little has been achieved in the pharmaceutical industry to combat this problem. This has led researchers and the medical field to revisit past drugs that were deemed too toxic for clinical use. In particular, the cyclic cationic peptides polymyxin B and colistin, which are specific for Gram-negative bacteria, have been used as "last resort" antimicrobials. Before the 1980s, these drugs were known for their renal and neural toxicities; however, new clinical practices and possibly improved manufacturing have made them safer to use. Previously suggested to primarily attack the membranes of Gram-negative bacteria and to not easily select for resistant mutants, recent research exploring resistance and mechanisms of action has provided new perspectives. This review focuses primarily on the proposed alternative mechanisms of action, known resistance mechanisms, and how these support the alternative mechanisms of action.
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Affiliation(s)
- Michael J Trimble
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Patrik Mlynárčik
- Department of Microbiology, Faculty of Medicine and Dentistry, Palacký University, 771 47 Olomouc, Czech Republic
| | - Milan Kolář
- Department of Microbiology, Faculty of Medicine and Dentistry, Palacký University, 771 47 Olomouc, Czech Republic
| | - Robert E W Hancock
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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19
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Baron S, Hadjadj L, Rolain JM, Olaitan AO. Molecular mechanisms of polymyxin resistance: knowns and unknowns. Int J Antimicrob Agents 2016; 48:583-591. [PMID: 27524102 DOI: 10.1016/j.ijantimicag.2016.06.023] [Citation(s) in RCA: 283] [Impact Index Per Article: 35.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 06/14/2016] [Accepted: 06/23/2016] [Indexed: 12/19/2022]
Abstract
Colistin, also referred to as polymyxin E, is an effective antibiotic against most multidrug-resistant Gram-negative bacteria and is currently used as a last-line drug for treating severe bacterial infections. Colistin resistance has increased gradually for the last few years, and knowledge of its multifaceted mechanisms is expanding. This includes the newly discovered plasmid-mediated colistin resistance gene mcr-1, which has been detected in over 20 countries within 3 months of its first report. We previously reported all of the known mechanisms of polymyxin resistance in our first review in 2014, but an update seems necessary in 2016, considering the significant recent discoveries that have been made in this domain. This review provides an update about what is already known, what is new, and some unresolved questions with respect to colistin resistance.
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Affiliation(s)
- Sophie Baron
- Unité de recherche sur les maladies infectieuses et tropicales émergentes (URMITE), CNRS-IRD UMR 6236, Méditerranée Infection, Faculté de Médecine et de Pharmacie, Aix-Marseille Université, Marseille, France
| | - Linda Hadjadj
- Unité de recherche sur les maladies infectieuses et tropicales émergentes (URMITE), CNRS-IRD UMR 6236, Méditerranée Infection, Faculté de Médecine et de Pharmacie, Aix-Marseille Université, Marseille, France
| | - Jean-Marc Rolain
- Unité de recherche sur les maladies infectieuses et tropicales émergentes (URMITE), CNRS-IRD UMR 6236, Méditerranée Infection, Faculté de Médecine et de Pharmacie, Aix-Marseille Université, Marseille, France.
| | - Abiola Olumuyiwa Olaitan
- Unité de recherche sur les maladies infectieuses et tropicales émergentes (URMITE), CNRS-IRD UMR 6236, Méditerranée Infection, Faculté de Médecine et de Pharmacie, Aix-Marseille Université, Marseille, France.
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Joo HS, Fu CI, Otto M. Bacterial strategies of resistance to antimicrobial peptides. Philos Trans R Soc Lond B Biol Sci 2016; 371:20150292. [PMID: 27160595 PMCID: PMC4874390 DOI: 10.1098/rstb.2015.0292] [Citation(s) in RCA: 205] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/18/2016] [Indexed: 02/06/2023] Open
Abstract
Antimicrobial peptides (AMPs) are a key component of the host's innate immune system, targeting invasive and colonizing bacteria. For successful survival and colonization of the host, bacteria have a series of mechanisms to interfere with AMP activity, and AMP resistance is intimately connected with the virulence potential of bacterial pathogens. In particular, because AMPs are considered as potential novel antimicrobial drugs, it is vital to understand bacterial AMP resistance mechanisms. This review gives a comparative overview of Gram-positive and Gram-negative bacterial strategies of resistance to various AMPs, such as repulsion or sequestration by bacterial surface structures, alteration of membrane charge or fluidity, degradation and removal by efflux pumps.This article is part of the themed issue 'Evolutionary ecology of arthropod antimicrobial peptides'.
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Affiliation(s)
- Hwang-Soo Joo
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases (NIAID), US National Institutes of Health (NIH), 50 South Drive, Bethesda, MD 20892, USA
| | - Chih-Iung Fu
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases (NIAID), US National Institutes of Health (NIH), 50 South Drive, Bethesda, MD 20892, USA
| | - Michael Otto
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases (NIAID), US National Institutes of Health (NIH), 50 South Drive, Bethesda, MD 20892, USA
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21
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Joo HS, Fu CI, Otto M. Bacterial strategies of resistance to antimicrobial peptides. Philos Trans R Soc Lond B Biol Sci 2016. [PMID: 27160595 DOI: 10.1098/rstb.2015.0292.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Antimicrobial peptides (AMPs) are a key component of the host's innate immune system, targeting invasive and colonizing bacteria. For successful survival and colonization of the host, bacteria have a series of mechanisms to interfere with AMP activity, and AMP resistance is intimately connected with the virulence potential of bacterial pathogens. In particular, because AMPs are considered as potential novel antimicrobial drugs, it is vital to understand bacterial AMP resistance mechanisms. This review gives a comparative overview of Gram-positive and Gram-negative bacterial strategies of resistance to various AMPs, such as repulsion or sequestration by bacterial surface structures, alteration of membrane charge or fluidity, degradation and removal by efflux pumps.This article is part of the themed issue 'Evolutionary ecology of arthropod antimicrobial peptides'.
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Affiliation(s)
- Hwang-Soo Joo
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases (NIAID), US National Institutes of Health (NIH), 50 South Drive, Bethesda, MD 20892, USA
| | - Chih-Iung Fu
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases (NIAID), US National Institutes of Health (NIH), 50 South Drive, Bethesda, MD 20892, USA
| | - Michael Otto
- Pathogen Molecular Genetics Section, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases (NIAID), US National Institutes of Health (NIH), 50 South Drive, Bethesda, MD 20892, USA
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Abstract
Cationic antimicrobial peptides (CAMPs) are important innate immune defenses that inhibit colonization by pathogens and contribute to clearance of infections. Gram-negative bacterial pathogens are a major target, yet many of them have evolved mechanisms to resist these antimicrobials. These resistance mechanisms can be critical contributors to bacterial virulence and are often crucial for survival within the host. Here, we summarize methods used by Gram-negative bacteria to resist CAMPs. Understanding these mechanisms may lead to new therapeutic strategies against pathogens with extensive CAMP resistance.
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Affiliation(s)
- Victor I. Band
- Department of Microbiology and Immunology, Emory University, Atlanta, GA 30329, USA; E-Mail:
- Yerkes Primate Research Center, Emory University, Atlanta, GA 30329, USA
- Emory Vaccine Center, Emory University, Atlanta, GA 30329, USA
| | - David S. Weiss
- Yerkes Primate Research Center, Emory University, Atlanta, GA 30329, USA
- Emory Vaccine Center, Emory University, Atlanta, GA 30329, USA
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30329, USA
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-404-727-8214; Fax: +1-404-727-8199
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A PmrB-Regulated Deacetylase Required for Lipid A Modification and Polymyxin Resistance in Acinetobacter baumannii. Antimicrob Agents Chemother 2015; 59:7911-4. [PMID: 26459891 DOI: 10.1128/aac.00515-15] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 10/03/2015] [Indexed: 11/20/2022] Open
Abstract
Emerging resistance to "last-resort" polymyxin antibiotics in Gram-negative bacteria is a significant threat to public health. We identified the Acinetobacter baumannii NaxD deacetylase as a critical mediator of lipid A modification resulting in polymyxin resistance and demonstrated that naxD is regulated by the sensor kinase PmrB. This represents the first description of a specific PmrB-regulated gene contributing to polymyxin resistance in A. baumannii and highlights NaxD as a putative drug target to reverse polymyxin resistance.
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Stephens MD, Hubble VB, Ernst RK, van Hoek ML, Melander RJ, Cavanagh J, Melander C. Potentiation of Francisella Resistance to Conventional Antibiotics through Small Molecule Adjuvants. MEDCHEMCOMM 2015; 7:128-131. [PMID: 26877862 DOI: 10.1039/c5md00353a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A screen of 20 compounds identified small molecule adjuvants capable of potentiating anitbiotic activty against Francisella philomiragia. Analogue synthesis of an initial hit compound led to the discovery of a potentially new class of small molecule adjuvants containg an indole core. The lead compound was able to lower the MIC of colistin by 32-fold against intrinsically resistant F. philomiragia.
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Affiliation(s)
- Matthew D Stephens
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Veroncia B Hubble
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Robert K Ernst
- Department of Microbial Pathogenesis, University of Maryland - Baltimore, Baltimore, MD 21201, United States
| | - Monique L van Hoek
- School of Systems Biology & National Center for Biodefense and Infectious Diseases, George Mason University, Manassas, VA 20110, United States
| | - Roberta J Melander
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - John Cavanagh
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Christian Melander
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United States
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Nuri R, Shprung T, Shai Y. Defensive remodeling: How bacterial surface properties and biofilm formation promote resistance to antimicrobial peptides. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:3089-100. [PMID: 26051126 DOI: 10.1016/j.bbamem.2015.05.022] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 05/25/2015] [Accepted: 05/26/2015] [Indexed: 11/15/2022]
Abstract
Multidrug resistance bacteria are a major concern worldwide. These pathogens cannot be treated with conventional antibiotics and thus alternative therapeutic agents are needed. Antimicrobial peptides (AMPs) are considered to be good candidates for this purpose. Most AMPs are short and positively charged amphipathic peptides, which are found in all known forms of life. AMPs are known to kill bacteria by binding to the negatively charged bacterial surface, and in most cases cause membrane disruption. Resistance toward AMPs can be developed, by modification of bacterial surface molecules, secretion of protective material and up-regulation or elimination of specific proteins. Because of the general mechanisms of attachment and action of AMPs, bacterial resistance to AMPs often involves biophysical and biochemical changes such as surface rigidity, cell wall thickness, surface charge, as well as membrane and cell wall modification. Here we focus on the biophysical, surface and surrounding changes that bacteria undergo in acquiring resistance to AMPs. In addition we discuss the question of whether bacterial resistance to administered AMPs might compromise our innate immunity to endogenous AMPs. This article is part of a Special Issue entitled: Bacterial Resistance to Antimicrobial Peptides.
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Affiliation(s)
- Reut Nuri
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Tal Shprung
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yechiel Shai
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel.
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Bauer ME, Shafer WM. On the in vivo significance of bacterial resistance to antimicrobial peptides. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:3101-11. [PMID: 25701234 DOI: 10.1016/j.bbamem.2015.02.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Revised: 02/04/2015] [Accepted: 02/07/2015] [Indexed: 12/17/2022]
Abstract
Antimicrobial peptides (AMPs) are at the front-line of host defense during infection and play critical roles both in reducing the microbial load early during infection and in linking innate to adaptive immunity. However, successful pathogens have developed mechanisms to resist AMPs. Although considerable progress has been made in elucidating AMP-resistance mechanisms of pathogenic bacteria in vitro, less is known regarding the in vivo significance of such resistance. Nevertheless, progress has been made in this area, largely by using murine models and, in two instances, human models of infection. Herein, we review progress on the use of in vivo infection models in AMP research and discuss the AMP resistance mechanisms that have been established by in vivo studies to contribute to microbial infection. We posit that in vivo infection models are essential tools for investigators to understand the significance to pathogenesis of genetic changes that impact levels of bacterial susceptibility to AMPs. This article is part of a Special Issue entitled: Bacterial Resistance to Antimicrobial Peptides.
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Affiliation(s)
- Margaret E Bauer
- Department of Microbiology and Immunology, Indiana University School of Medicine, 635 Barnhill Drive MS-420, Indianapolis, IN 46254, USA.
| | - William M Shafer
- Laboratories of Bacterial Pathogenesis, Veterans Affairs Medical Center, Decatur, GA 30033, USA; Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322, USA.
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27
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Heimlich DR, Harrison A, Mason KM. Host Antimicrobial Peptides in Bacterial Homeostasis and Pathogenesis of Disease. Antibiotics (Basel) 2014; 3:645-76. [PMID: 26029470 PMCID: PMC4448142 DOI: 10.3390/antibiotics3040645] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 11/05/2014] [Accepted: 11/05/2014] [Indexed: 01/10/2023] Open
Abstract
Innate immune responses function as a first line of host defense against the development of bacterial infection, and in some cases to preserve the sterility of privileged sites in the human host. Bacteria that enter these sites must counter host responses for colonization. From the host's perspective, the innate immune system works expeditiously to minimize the bacterial threat before colonization and subsequent dysbiosis. The multifactorial nature of disease further challenges predictions of how each independent variable influences bacterial pathogenesis. From bacterial colonization to infection and through disease, the microenvironments of the host are in constant flux as bacterial and host factors contribute to changes at the host-pathogen interface, with the host attempting to eradicate bacteria and the bacteria fighting to maintain residency. A key component of this innate host response towards bacterial infection is the production of antimicrobial peptides (AMPs). As an early component of the host response, AMPs modulate bacterial load and prevent establishment of infection. Under quiescent conditions, some AMPs are constitutively expressed by the epithelium. Bacterial infection can subsequently induce production of other AMPs in an effort to maintain sterility, or to restrict colonization. As demonstrated in various studies, the absence of a single AMP can influence pathogenesis, highlighting the importance of AMP concentration in maintaining homeostasis. Yet, AMPs can increase bacterial virulence through the co-opting of the peptides or alteration of bacterial virulence gene expression. Further, bacterial factors used to subvert AMPs can modify host microenvironments and alter colonization of the residential flora that principally maintain homeostasis. Thus, the dynamic interplay between host defense peptides and bacterial factors produced to quell peptide activity play a critical role in the progression and outcome of disease.
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Affiliation(s)
- Derek R. Heimlich
- The Research Institute at Nationwide Children’s Center for Microbial Pathogenesis, Columbus, OH 43205, USA; E-Mails: (D.R.H.); (A.H.)
| | - Alistair Harrison
- The Research Institute at Nationwide Children’s Center for Microbial Pathogenesis, Columbus, OH 43205, USA; E-Mails: (D.R.H.); (A.H.)
| | - Kevin M. Mason
- The Research Institute at Nationwide Children’s Center for Microbial Pathogenesis, Columbus, OH 43205, USA; E-Mails: (D.R.H.); (A.H.)
- The Ohio State University College of Medicine, Department of Pediatrics, Columbus, OH 43205, USA
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Unique structural modifications are present in the lipopolysaccharide from colistin-resistant strains of Acinetobacter baumannii. Antimicrob Agents Chemother 2013; 57:4831-40. [PMID: 23877686 DOI: 10.1128/aac.00865-13] [Citation(s) in RCA: 129] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Acinetobacter baumannii is a nosocomial opportunistic pathogen that can cause severe infections, including hospital-acquired pneumonia, wound infections, and sepsis. Multidrug-resistant (MDR) strains are prevalent, further complicating patient treatment. Due to the increase in MDR strains, the cationic antimicrobial peptide colistin has been used to treat A. baumannii infections. Colistin-resistant strains of A. baumannii with alterations to the lipid A component of lipopolysaccharide (LPS) have been reported; specifically, the lipid A structure was shown to be hepta-acylated with a phosphoethanolamine (pEtN) modification present on one of the terminal phosphate residues. Using a tandem mass spectrometry platform, we provide definitive evidence that the lipid A isolated from colistin-resistant A. baumannii MAC204 LPS contains a novel structure corresponding to a diphosphoryl hepta-acylated lipid A structure with both pEtN and galactosamine (GalN) modifications. To correlate our structural studies with clinically relevant samples, we characterized colistin-susceptible and -resistant isolates obtained from patients. These results demonstrated that the clinical colistin-resistant isolate had the same pEtN and GalN modifications as those seen in the laboratory-adapted A. baumannii strain MAC204. In summary, this work has shown complete structure characterization including the accurate assignment of acylation, phosphorylation, and glycosylation of lipid A from A. baumannii, which are important for resistance to colistin.
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Okan NA, Kasper DL. The atypical lipopolysaccharide of Francisella. Carbohydr Res 2013; 378:79-83. [PMID: 23916469 DOI: 10.1016/j.carres.2013.06.015] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 06/15/2013] [Accepted: 06/20/2013] [Indexed: 01/17/2023]
Abstract
Bacterial lipopolysaccharides (LPSs) are ubiquitous molecules that are prominent components of the outer membranes of most gram-negative bacteria. Genetic and structural characterizations of Francisella LPS have revealed substantial differences when compared to more commonly studied LPSs of the Enterobacteriaceae. This review discusses both the general characteristics and the unusual features of Francisella LPS.
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Affiliation(s)
- Nihal A Okan
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, United States
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Shah NR, Albitar-Nehme S, Kim E, Marr N, Novikov A, Caroff M, Fernandez RC. Minor modifications to the phosphate groups and the C3' acyl chain length of lipid A in two Bordetella pertussis strains, BP338 and 18-323, independently affect Toll-like receptor 4 protein activation. J Biol Chem 2013; 288:11751-60. [PMID: 23467413 DOI: 10.1074/jbc.m112.434365] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lipopolysaccharides (LPS) of Bordetella pertussis are important modulators of the immune system. Interaction of the lipid A region of LPS with the Toll-like receptor 4 (TLR4) complex causes dimerization of TLR4 and activation of downstream nuclear factor κB (NFκB), which can lead to inflammation. We have previously shown that two strains of B. pertussis, BP338 (a Tohama I-derivative) and 18-323, display two differences in lipid A structure. 1) BP338 can modify the 1- and 4'-phosphates by the addition of glucosamine (GlcN), whereas 18-323 cannot, and 2) the C3' acyl chain in BP338 is 14 carbons long, but only 10 or 12 carbons long in 18-323. In addition, BP338 lipid A can activate TLR4 to a greater extent than 18-323 lipid A. Here we set out to determine the genetic reasons for the differences in these lipid A structures and the contribution of each structural difference to the ability of lipid A to activate TLR4. We show that three genes of the lipid A GlcN modification (Lgm) locus, lgmA, lgmB, and lgmC (previously locus tags BP0399-BP0397), are required for GlcN modification and a single amino acid difference in LpxA is responsible for the difference in C3' acyl chain length. Furthermore, by introducing lipid A-modifying genes into 18-323 to generate isogenic strains with varying penta-acyl lipid A structures, we determined that both modifications increase TLR4 activation, although the GlcN modification plays a dominant role. These results shed light on how TLR4 may interact with penta-acyl lipid A species.
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Affiliation(s)
- Nita R Shah
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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