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Chain C, Sheehan JP, Xu X, Ghaffari S, Godbole A, Kim H, Freundlich JS, Rabinowitz JD, Gitai Z. A folate inhibitor exploits metabolic differences in Pseudomonas aeruginosa for narrow-spectrum targeting. Nat Microbiol 2024; 9:1207-1219. [PMID: 38594311 PMCID: PMC11087268 DOI: 10.1038/s41564-024-01665-2] [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: 10/17/2023] [Accepted: 03/06/2024] [Indexed: 04/11/2024]
Abstract
Pseudomonas aeruginosa is a leading cause of hospital-acquired infections for which the development of antibiotics is urgently needed. Unlike most enteric bacteria, P. aeruginosa lacks enzymes required to scavenge exogenous thymine. An appealing strategy to selectively target P. aeruginosa is to disrupt thymidine synthesis while providing exogenous thymine. However, known antibiotics that perturb thymidine synthesis are largely inactive against P. aeruginosa.Here we characterize fluorofolin, a dihydrofolate reductase (DHFR) inhibitor derived from Irresistin-16, that exhibits significant activity against P. aeruginosa in culture and in a mouse thigh infection model. Fluorofolin is active against a wide range of clinical P. aeruginosa isolates resistant to known antibiotics. Metabolomics and in vitro assays using purified folA confirm that fluorofolin inhibits P. aeruginosa DHFR. Importantly, in the presence of thymine supplementation, fluorofolin activity is selective for P. aeruginosa. Resistance to fluorofolin can emerge through overexpression of the efflux pumps MexCD-OprJ and MexEF-OprN, but these mutants also decrease pathogenesis. Our findings demonstrate how understanding species-specific genetic differences can enable selective targeting of important pathogens while revealing trade-offs between resistance and pathogenesis.
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Affiliation(s)
- Connor Chain
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Joseph P Sheehan
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Xincheng Xu
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Chemistry, Princeton University, Princeton, NJ, USA
| | - Soodabeh Ghaffari
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Aneesh Godbole
- Department of Pharmacology, Physiology and Neuroscience, Rutgers University - New Jersey Medical School, Newark, NJ, USA
| | - Hahn Kim
- Department of Chemistry, Princeton University, Princeton, NJ, USA
- Small Molecule Screening Center, Princeton University, Princeton, NJ, USA
| | - Joel S Freundlich
- Department of Pharmacology, Physiology and Neuroscience, Rutgers University - New Jersey Medical School, Newark, NJ, USA
- Division of Infectious Disease, Department of Medicine and the Ruy V. Lourenço Center for the Study of Emerging and Re-emerging Pathogens, Rutgers University - New Jersey Medical School, Newark, NJ, USA
| | - Joshua D Rabinowitz
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Department of Chemistry, Princeton University, Princeton, NJ, USA
- Ludwig Institute for Cancer Research, Princeton Branch, Princeton University, Princeton, NJ, USA
| | - Zemer Gitai
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA.
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Summer M, Ali S, Tahir HM, Abaidullah R, Fiaz U, Mumtaz S, Fiaz H, Hassan A, Mughal TA, Farooq MA. Mode of Action of Biogenic Silver, Zinc, Copper, Titanium and Cobalt Nanoparticles Against Antibiotics Resistant Pathogens. J Inorg Organomet Polym Mater 2024; 34:1417-1451. [DOI: 10.1007/s10904-023-02935-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 11/02/2023] [Indexed: 08/04/2024]
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Wang Z, Ma R, Chen B, Yu X, Wang X, Zuo X, Liang B, Yang J. A transcription factor-based bacterial biosensor system and its application for on-site detection of explosives. Biosens Bioelectron 2024; 244:115805. [PMID: 37948915 DOI: 10.1016/j.bios.2023.115805] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 10/01/2023] [Accepted: 10/29/2023] [Indexed: 11/12/2023]
Abstract
Detecting unexploded landmines is critical due to the environmental pollution and potential humanitarian risks caused by buried landmines. Therefore, this study focused on developing a biosensor system capable of detecting explosives safely and efficiently. A novel transcription factor-based Escherichia coli biosensor was designed to detect 1,3-dinitrobenzene (1,3-DNB). The MexT transcription factor from Pseudomonas putida (P. putida) was identified as the fundamental sensing element in this biosensor. The study found that MexT positively regulated the transcription of PP_2827 by binding to the bidirectional promoter region between them, and significantly enhanced the expression of downstream genes under the condition of 1,3-DNB. The MexT-based biosensor for 1,3-DNB was developed by adopting different combinations of the mexT gene and promoters. The optimized biosensor demonstrated adequate sensitivity for detecting 0.1 μg/mL of 1,3-DNB in a liquid solution with satisfactory specificity and long-term stability. Subsequently, the MexT-based biosensor was integrated into a detection device to simulate the in-field exploration of explosives. The system exhibited a detection sensitivity of 0.5 mg/kg for 1,3-DNB in the sand, and realized the detection of on-site and large-scale area and the location of buried 1,3-DNB under the soil. The study provided a novel transcription factor-based bacterial biosensor and a complete system (China Earth Eye, CEE) for sensitive detection of 1,3-DNB. The good performance of this biosensor system can facilitate the development of accurate, on-site, and high-efficient exploration of explosives in real extensive minefields. Moreover, this 1,3-DNB biosensor can be complementary to the 2,4-DNT biosensor reported before, demonstrating its potential applications in military situations.
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Affiliation(s)
- Zhaobao Wang
- Energy-rich Compound Production by Photosynthetic Carbon Fixation Research Center, Shandong Key Lab of Applied Mycology, College of Life Sciences, Qingdao Agricultural University, PR China
| | - Ran Ma
- Energy-rich Compound Production by Photosynthetic Carbon Fixation Research Center, Shandong Key Lab of Applied Mycology, College of Life Sciences, Qingdao Agricultural University, PR China
| | - Bingjing Chen
- Energy-rich Compound Production by Photosynthetic Carbon Fixation Research Center, Shandong Key Lab of Applied Mycology, College of Life Sciences, Qingdao Agricultural University, PR China
| | - Xiaotong Yu
- Energy-rich Compound Production by Photosynthetic Carbon Fixation Research Center, Shandong Key Lab of Applied Mycology, College of Life Sciences, Qingdao Agricultural University, PR China
| | - Xue Wang
- Energy-rich Compound Production by Photosynthetic Carbon Fixation Research Center, Shandong Key Lab of Applied Mycology, College of Life Sciences, Qingdao Agricultural University, PR China
| | - Xinyun Zuo
- Energy-rich Compound Production by Photosynthetic Carbon Fixation Research Center, Shandong Key Lab of Applied Mycology, College of Life Sciences, Qingdao Agricultural University, PR China
| | - Bo Liang
- Energy-rich Compound Production by Photosynthetic Carbon Fixation Research Center, Shandong Key Lab of Applied Mycology, College of Life Sciences, Qingdao Agricultural University, PR China.
| | - Jianming Yang
- Energy-rich Compound Production by Photosynthetic Carbon Fixation Research Center, Shandong Key Lab of Applied Mycology, College of Life Sciences, Qingdao Agricultural University, PR China.
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Manrique PD, López CA, Gnanakaran S, Rybenkov VV, Zgurskaya HI. New understanding of multidrug efflux and permeation in antibiotic resistance, persistence, and heteroresistance. Ann N Y Acad Sci 2023; 1519:46-62. [PMID: 36344198 PMCID: PMC9839546 DOI: 10.1111/nyas.14921] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Antibiotics effective against Gram-negative ESKAPE pathogens are a critical area of unmet need. Infections caused by these pathogens are not only difficult to treat but finding new therapies to overcome Gram-negative resistance is also a challenge. There are not enough antibiotics in development that target the most dangerous pathogens and there are not enough novel drugs in the pipeline. The major obstacle in the antibiotic discovery pipeline is the lack of understanding of how to breach antibiotic permeability barriers of Gram-negative pathogens. These barriers are created by active efflux pumps acting across both the inner and the outer membranes. Overproduction of efflux pumps alone or together with either modification of the outer membrane or antibiotic-inactivating enzymes and target mutations contribute to clinical levels of antibiotics resistance. Recent efforts have generated significant advances in the rationalization of compound efflux and permeation across the cell envelopes of Gram-negative pathogens. Combined with earlier studies and novel mathematical models, these efforts have led to a multilevel understanding of how antibiotics permeate these barriers and how multidrug efflux and permeation contribute to the development of antibiotic resistance and heteroresistance. Here, we discuss the new developments in this area.
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Affiliation(s)
- Pedro D. Manrique
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM 87545, United States
- Present address: Physics Department, George Washington University, Washington D.C. 20052, United States
| | - Cesar A. López
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM 87545, United States
| | - S. Gnanakaran
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, NM 87545, United States
| | - Valentin V. Rybenkov
- Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, United States
| | - Helen I. Zgurskaya
- Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, OK 73019, United States
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Bové M, Kolpen M, Lichtenberg M, Bjarnsholt T, Coenye T. Adaptation of Pseudomonas aeruginosa biofilms to tobramycin and the quorum sensing inhibitor C-30 during experimental evolution requires multiple genotypic and phenotypic changes. MICROBIOLOGY (READING, ENGLAND) 2023; 169:001278. [PMID: 36748633 PMCID: PMC9993117 DOI: 10.1099/mic.0.001278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
In the present study we evaluated the fitness, antimicrobial susceptibility, metabolic activity, gene expression, in vitro production of virulence factors and in vivo virulence of experimentally evolved Pseudomonas aeruginosa PAO1. These strains were previously evolved in the presence of tobramycin and the quorum sensing inhibitor furanone C-30 (C-30) and carried mutations in mexT and fusA1. Compared to the wild-type (WT), the evolved strains show a different growth rate and different metabolic activity, suggesting they have an altered fitness. mexT mutants were less susceptible to C-30 than WT strains; they also show reduced susceptibility to chloramphenicol and ciprofloxacin, two substrates of the MexEF-OprN efflux pump. fusA1 mutants had a decreased susceptibility to aminoglycoside antibiotics, and an increased susceptibility to chloramphenicol. The decreased antimicrobial susceptibility and decreased susceptibility to C-30 was accompanied by a changed metabolic activity profile during treatment. The expression of mexE was significantly increased in mexT mutants and induced by C-30, suggesting that MexEF-OprN exports C-30 out of the bacterial cell. The in vitro production of virulence factors as well as virulence in two in vivo models of the strains evolved in the presence of C-30 was unchanged compared to the virulence of the WT. Finally, the evolved strains were less susceptible towards tobramycin (alone and combined with C-30) in an in vivo mouse model. In conclusion, this study shows that mutations acquired during experimental evolution of P. aeruginosa biofilms in the presence of tobramycin and C-30, are accompanied by an altered fitness, metabolism, mexE expression and in vitro and in vivo antimicrobial susceptibility.
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Affiliation(s)
- Mona Bové
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| | - Mette Kolpen
- Department of Clinical Microbiology, Rigshospitalet, 2200 Copenhagen N, Denmark
| | - Mads Lichtenberg
- Costerton Biofilm Center, Department of Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Bjarnsholt
- Costerton Biofilm Center, Department of Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark
| | - Tom Coenye
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium.,Costerton Biofilm Center, Department of Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark
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Low Ciprofloxacin Concentrations Select Multidrug-Resistant Mutants Overproducing Efflux Pumps in Clinical Isolates of Pseudomonas aeruginosa. Microbiol Spectr 2022; 10:e0072322. [PMID: 36000896 PMCID: PMC9603996 DOI: 10.1128/spectrum.00723-22] [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] [Indexed: 12/30/2022] Open
Abstract
Low antibiotic concentrations present in natural environments are a severe and often neglected threat to public health. Even if they are present below their MICs, they may select for antibiotic-resistant pathogens. Notably, the minimal subinhibitory concentrations that select resistant bacteria, and define the respective sub-MIC selective windows, differ between antibiotics. The establishment of these selective concentrations is needed for risk-assessment studies regarding the presence of antibiotics in different habitats. Using short-term evolution experiments in a set of 12 Pseudomonas aeruginosa clinical isolates (including high-risk clones with ubiquitous distribution), we have determined that ciprofloxacin sub-MIC selective windows are strain specific and resistome dependent. Nonetheless, in all cases, clinically relevant multidrug-resistant (MDR) mutants emerged upon exposure to low ciprofloxacin concentrations, with these concentrations being below the levels reported in ciprofloxacin-polluted natural habitats where P. aeruginosa can be present. This feature expands the conditions and habitats where clinically relevant quinolone-resistant mutants can emerge. In addition, we established the lowest concentration threshold beyond which P. aeruginosa, regardless of the strain, becomes resistant to ciprofloxacin. Three days of exposure under this sub-MIC "risk concentration" led to the selection of MDR mutants that displayed resistance mechanisms usually ascribed to high selective pressures, i.e., the overproduction of the efflux pumps MexCD-OprJ and MexEF-OprN. From a One-Health viewpoint, these data stress the transcendent role of low drug concentrations, which can be encountered in natural ecosystems, in aggravating the antibiotic resistance problem, especially when it comes to pathogens of environmental origin. IMPORTANCE It has been established that antibiotic concentrations below MICs can select antibiotic-resistant pathogens, a feature of relevance for analyzing the role of nonclinical ecosystems in antibiotic resistance evolution. The range of concentrations where this selection occurs defines the sub-MIC selective window, whose width depends on the antibiotic. Herein, we have determined the ciprofloxacin sub-MIC selective windows of a set of Pseudomonas aeruginosa clinical isolates (including high-risk clones with worldwide distribution) and established the lowest concentration threshold, notably an amount reported to be present in natural ecosystems, beyond which this pathogen acquires resistance. Importantly, our results show that this ciprofloxacin sub-MIC selects for multidrug-resistant mutants overproducing clinically relevant efflux pumps. From a One-Health angle, this information supports that low antimicrobial concentrations, present in natural environments, may have a relevant role in worsening the antibiotic resistance crisis, particularly regarding pathogens with environmental niches, such as P. aeruginosa.
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Hulen C, Racine PJ, Feuilloley M, Elomri A, Lomri NE. Effects of Verapamil and Two Bisbenzylisoquinolines, Curine and Guattegaumerine Extracted from Isolona hexaloba, on the Inhibition of ABC Transporters from Pseudomonas aeruginosa. Antibiotics (Basel) 2022; 11:antibiotics11050700. [PMID: 35625344 PMCID: PMC9137725 DOI: 10.3390/antibiotics11050700] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Revised: 05/13/2022] [Accepted: 05/17/2022] [Indexed: 02/05/2023] Open
Abstract
The biological effects of alkaloids, curine, guattegaumerine, and verapamil, on Pseudomonas aeruginosa were investigated. These molecules did not inhibit P. aeruginosa growth but increased the sensitivity of this bacterium to carbenicillin, novobiocin, and erythromycin. The results of another study indicate that curine and guattegaumerine were competitors of verapamil and acted as inhibitors of eukaryotic ABCB1 efflux pump. A BLAST-P carried out between a bacterial MDR transporter LmrA from Lactococcus lactis, a human MDR1/P-glycoprotein (ABCB1), and ABC proteins of P.aeruginosa highlighted five potential candidates that have this bacterium. A study on the sensitivity to carbenicillin in the presence of verapamil allowed us to identify the product of gene PA1113 as the ABC transporter involved in the influx of carbenicillin. Similarly, novobiocin transport performed in the presence of verapamil and a docking analysis highlighted protein MsbA (Lipid A flippase, gene PA4997) as a potential candidate in novobiocin efflux. MsbA has previously been identified as a multidrug transporter in E. coli, and as P. aeruginosa MsbA presented 76% identity with E. coli MsbA, it is possible that novobiocin efflux involves this ABC transporter, accounting for about 30% of the bacterium resistance to this antibiotic.
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Affiliation(s)
- Christian Hulen
- Bacterial Communication and Antimicrobial Strategies Research Unit, University of Rouen Normandy, 55 Rue Saint Germain, 2700 Evreux, France; (C.H.); (P.-J.R.); (M.F.)
| | - Pierre-Jean Racine
- Bacterial Communication and Antimicrobial Strategies Research Unit, University of Rouen Normandy, 55 Rue Saint Germain, 2700 Evreux, France; (C.H.); (P.-J.R.); (M.F.)
| | - Marc Feuilloley
- Bacterial Communication and Antimicrobial Strategies Research Unit, University of Rouen Normandy, 55 Rue Saint Germain, 2700 Evreux, France; (C.H.); (P.-J.R.); (M.F.)
| | - Abdelhakim Elomri
- UNIROUEN, INSA Rouen, CNRS, COBRA (UMR 6014), Normandie University, 76000 Rouen, France;
| | - Nour-Eddine Lomri
- Bacterial Communication and Antimicrobial Strategies Research Unit, University of Rouen Normandy, 55 Rue Saint Germain, 2700 Evreux, France; (C.H.); (P.-J.R.); (M.F.)
- Department of Biology, UFR Sciences and Techniques, University of Cergy-Pontoise, 2 Ave A. Chauvin, 95302 Cergy-Pontoise, France
- Correspondence: ; Tel.: +33-1-3425-6555
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Streling AP, Cayô R, Nodari CS, Almeida LGP, Santos FF, Hanson B, Dinh AQ, Vasconcelos ATR, Miller WR, Arias CA, Gales AC. Genomic analysis of carbapenem-resistant Pseudomonas aeruginosa ST143 clone showing susceptibility to broad-spectrum cephalosporins. J Glob Antimicrob Resist 2021; 26:177-179. [PMID: 34175444 DOI: 10.1016/j.jgar.2021.05.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 04/11/2021] [Accepted: 05/22/2021] [Indexed: 12/01/2022] Open
Abstract
OBJECTIVES Using whole-genome sequencing (WGS), we aimed to characterise a Pseudomonas aeruginosa ST143 clinical strain (Pb9) that presented resistance to meropenem and imipenem and susceptibility to piperacillin/tazobactam and broad-spectrum cephalosporins. METHODS The antimicrobial susceptibility profile was confirmed by broth microdilution. WGS was performed using an Illumina MiSeq platform to identify possible genetic determinants of β-lactam resistance. Transcription levels of chromosomally encoded efflux systems and oprD were evaluated by RT-qPCR. RESULTS WGS analysis showed that no acquired carbapenemase-encoding gene was found in isolate Pb9, although mutations in the chromosomally encoded β-lactamase genes blaOXA-488, blaPIB-1 and blaPDC-5 were observed. In addition, we detected a premature stop codon in the major porin-encoding gene oprD coupled with hyperexpression of MexAB-OprM and MexEF-OprN. CONCLUSION Our results suggest that the β-lactam resistance phenotype presented by strain Pb9 might be related to an association of OprD loss with hyperexpression of the efflux pump systems MexAB-OprM and MexEF-OprN. However, the contribution of OXA-488, PDC-5 and PIB-1 to this phenotype remains unclear and warrants further investigation.
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Affiliation(s)
- Ana Paula Streling
- Universidade Federal de São Paulo (UNIFESP), Laboratório Alerta, Division of Infectious Diseases, Department of Internal Medicine-Escola Paulista de Medicina (EPM), São Paulo - SP, Brazil.
| | - Rodrigo Cayô
- Universidade Federal de São Paulo (UNIFESP), Laboratório Alerta, Division of Infectious Diseases, Department of Internal Medicine-Escola Paulista de Medicina (EPM), São Paulo - SP, Brazil; Universidade Federal de São Paulo (UNIFESP), Laboratório de Imunologia e Microbiologia (LIB), Setor de Biologia Molecular, Microbiologia e Imunologia, Departamento de Ciências Biológicas (DCB), Instituto de Ciências Ambientais, Químicas e Farmacêuticas (ICAQF), Diadema - SP, Brazil
| | - Carolina S Nodari
- Universidade Federal de São Paulo (UNIFESP), Laboratório Alerta, Division of Infectious Diseases, Department of Internal Medicine-Escola Paulista de Medicina (EPM), São Paulo - SP, Brazil
| | - Luiz G P Almeida
- National Laboratory for Scientific Computing (LNCC), Petrópolis - RJ, Brazil
| | - Fernanda F Santos
- Universidade Federal de São Paulo (UNIFESP), Laboratório Alerta, Division of Infectious Diseases, Department of Internal Medicine-Escola Paulista de Medicina (EPM), São Paulo - SP, Brazil
| | - Blake Hanson
- Center for Antimicrobial Resistance and Microbial Genomics, University of Texas Health Science Center, Houston, TX, USA; Division of Infectious Diseases, and Department of Pathology and Laboratory Medicine, University of Texas Health Science Center, McGovern School of Medicine, Houston, TX, USA; Center for Infectious Diseases, University of Texas Health Science Center, School of Public Health, Houston, TX, USA
| | - An Q Dinh
- Center for Antimicrobial Resistance and Microbial Genomics, University of Texas Health Science Center, Houston, TX, USA; Division of Infectious Diseases, and Department of Pathology and Laboratory Medicine, University of Texas Health Science Center, McGovern School of Medicine, Houston, TX, USA
| | | | - Willian R Miller
- Center for Antimicrobial Resistance and Microbial Genomics, University of Texas Health Science Center, Houston, TX, USA; Division of Infectious Diseases, and Department of Pathology and Laboratory Medicine, University of Texas Health Science Center, McGovern School of Medicine, Houston, TX, USA; Center for Infectious Diseases, University of Texas Health Science Center, School of Public Health, Houston, TX, USA
| | - Cesar A Arias
- Center for Antimicrobial Resistance and Microbial Genomics, University of Texas Health Science Center, Houston, TX, USA; Division of Infectious Diseases, and Department of Pathology and Laboratory Medicine, University of Texas Health Science Center, McGovern School of Medicine, Houston, TX, USA; Center for Infectious Diseases, University of Texas Health Science Center, School of Public Health, Houston, TX, USA; MD Anderson Cancer Center and UTHealth Graduate School of Biomedical Sciences, Houston, TX, USA
| | - Ana C Gales
- Universidade Federal de São Paulo (UNIFESP), Laboratório Alerta, Division of Infectious Diseases, Department of Internal Medicine-Escola Paulista de Medicina (EPM), São Paulo - SP, Brazil
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Xu C, Liu H, Pan X, Ma Z, Wang D, Zhang X, Zhu G, Bai F, Cheng Z, Wu W, Jin Y. Mechanisms for Development of Ciprofloxacin Resistance in a Clinical Isolate of Pseudomonas aeruginosa. Front Microbiol 2021; 11:598291. [PMID: 33488544 PMCID: PMC7819972 DOI: 10.3389/fmicb.2020.598291] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Accepted: 11/24/2020] [Indexed: 12/21/2022] Open
Abstract
Treatment of infections by Pseudomonas aeruginosa is difficult due to its high intrinsic and acquired antibiotic resistance. Upon colonization in the human hosts, P. aeruginosa accumulates genetic mutations that confer the bacterium antibiotic resistance and ability to better live in the host environment. Characterizing the evolutionary traits would provide important insights into the development of effective combinatory antibiotic therapies to cure P. aeruginosa infections. In this work, we performed a detailed analysis of the molecular mechanisms by which a clinical isolate (CSP18) yields a ciprofloxacin-resistant derivative (CRP42). Genomic DNA re-sequencing and RNAseq were carried out to compare the genomic mutational signature and transcriptional profiles between the two isolates. The results indicated that D87G mutation in GyrA, together with MexEF-OprN hyper-expression caused by F7S mutation in MexS, was responsible for the increased resistance to ciprofloxacin in the isolate CRP42. Further simulation of CRP42 by gene editing in CSP18 demonstrated that D87G mutation in GyrA rendered CSP18 a fourfold increase in minimum inhibitory concentration against ciprofloxacin, while F7S mutation in MexS conferred an additional eightfold increase. Our experimental results demonstrate for the first time that the clinically relevant F7S point mutation in MexS results in hyper-expression of the mexEF-oprN and thus confers P. aeruginosa resistance to ciprofloxacin.
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Affiliation(s)
- Congjuan Xu
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Huimin Liu
- Tianjin Union Medical Center, Nankai University Affiliated Hospital, Tianjin, China
| | - Xiaolei Pan
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Zhenzhen Ma
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Dan Wang
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Xinxin Zhang
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Guangbo Zhu
- Tianjin Union Medical Center, Nankai University Affiliated Hospital, Tianjin, China
| | - Fang Bai
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Zhihui Cheng
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Weihui Wu
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
| | - Yongxin Jin
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China
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Response of Pseudomonas aeruginosa to the Innate Immune System-Derived Oxidants Hypochlorous Acid and Hypothiocyanous Acid. J Bacteriol 2020; 203:JB.00300-20. [PMID: 33106346 PMCID: PMC7950407 DOI: 10.1128/jb.00300-20] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 10/08/2020] [Indexed: 01/06/2023] Open
Abstract
The bacterial pathogen Pseudomonas aeruginosa causes devastating infections in immunocompromised hosts, including chronic lung infections in cystic fibrosis patients. To combat infection, the host’s immune system produces the antimicrobial oxidants hypochlorous acid (HOCl) and hypothiocyanous acid (HOSCN). Little is known about how P. aeruginosa responds to and survives attack from these oxidants. To address this, we carried out two approaches: a mutant screen and transcriptional study. We identified the P. aeruginosa transcriptional regulator, RclR, which responds specifically to HOCl and HOSCN stress and is essential for protection against both oxidants. We uncovered a link between the P. aeruginosa transcriptional response to these oxidants and physiological processes associated with pathogenicity, including antibiotic resistance and the type 3 secretion system. Pseudomonas aeruginosa is a significant nosocomial pathogen and is associated with lung infections in cystic fibrosis (CF). Once established, P. aeruginosa infections persist and are rarely eradicated despite host immune cells producing antimicrobial oxidants, including hypochlorous acid (HOCl) and hypothiocyanous acid (HOSCN). There is limited knowledge as to how P. aeruginosa senses, responds to, and protects itself against HOCl and HOSCN and the contribution of such responses to its success as a CF pathogen. To investigate the P. aeruginosa response to these oxidants, we screened 707 transposon mutants, with mutations in regulatory genes, for altered growth following HOCl exposure. We identified regulators of antibiotic resistance, methionine biosynthesis, catabolite repression, and PA14_07340, the homologue of the Escherichia coli HOCl-sensor RclR (30% identical), which are required for protection against HOCl. We have shown that RclR (PA14_07340) protects specifically against HOCl and HOSCN stress and responds to both oxidants by upregulating the expression of a putative peroxiredoxin, rclX (PA14_07355). Transcriptional analysis revealed that while there was specificity in the response to HOCl (231 genes upregulated) and HOSCN (105 genes upregulated), there was considerable overlap, with 74 genes upregulated by both oxidants. These included genes encoding the type 3 secretion system, sulfur and taurine transport, and the MexEF-OprN efflux pump. RclR coordinates part of the response to both oxidants, including upregulation of pyocyanin biosynthesis genes, and, in the presence of HOSCN, downregulation of chaperone genes. These data indicate that the P. aeruginosa response to HOCl and HOSCN is multifaceted, with RclR playing an essential role. IMPORTANCE The bacterial pathogen Pseudomonas aeruginosa causes devastating infections in immunocompromised hosts, including chronic lung infections in cystic fibrosis patients. To combat infection, the host’s immune system produces the antimicrobial oxidants hypochlorous acid (HOCl) and hypothiocyanous acid (HOSCN). Little is known about how P. aeruginosa responds to and survives attack from these oxidants. To address this, we carried out two approaches: a mutant screen and transcriptional study. We identified the P. aeruginosa transcriptional regulator, RclR, which responds specifically to HOCl and HOSCN stress and is essential for protection against both oxidants. We uncovered a link between the P. aeruginosa transcriptional response to these oxidants and physiological processes associated with pathogenicity, including antibiotic resistance and the type 3 secretion system.
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Henriquez T, Baldow T, Lo YK, Weydert D, Brachmann A, Jung H. Involvement of MexS and MexEF-OprN in Resistance to Toxic Ion Chelators in Pseudomonas putida KT2440. Microorganisms 2020; 8:microorganisms8111782. [PMID: 33202537 PMCID: PMC7697342 DOI: 10.3390/microorganisms8111782] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 11/09/2020] [Accepted: 11/12/2020] [Indexed: 01/22/2023] Open
Abstract
Bacteria must be able to cope with harsh environments to survive. In Gram-negative bacteria like Pseudomonas species, resistance-nodulation-division (RND) transporters contribute to this task by pumping toxic compounds out of cells. Previously, we found that the RND system TtgABC of Pseudomonas putida KT2440 confers resistance to toxic metal chelators of the bipyridyl group. Here, we report that the incubation of a ttgB mutant in medium containing 2,2’-bipyridyl generated revertant strains able to grow in the presence of this compound. This trait was related to alterations in the pp_2827 locus (homolog of mexS in Pseudomonas aeruginosa). The deletion and complementation of pp_2827 confirmed the importance of the locus for the revertant phenotype. Furthermore, alteration in the pp_2827 locus stimulated expression of the mexEF-oprN operon encoding an RND efflux pump. Deletion and complementation of mexF confirmed that the latter system can compensate the growth defect of the ttgB mutant in the presence of 2,2’-bipyridyl. To our knowledge, this is the first report on a role of pp_2827 (mexS) in the regulation of mexEF-oprN in P. putida KT2440. The results expand the information about the significance of MexEF-OprN in the stress response of P. putida KT2440 and the mechanisms for coping with bipyridyl toxicity.
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Affiliation(s)
- Tania Henriquez
- Biozentrum, Mikrobiologie, Ludwig-Maximilians-Universität München, 82152 Martinsried, Germany; (T.H.); (T.B.); (Y.K.L.); (D.W.)
| | - Tom Baldow
- Biozentrum, Mikrobiologie, Ludwig-Maximilians-Universität München, 82152 Martinsried, Germany; (T.H.); (T.B.); (Y.K.L.); (D.W.)
| | - Yat Kei Lo
- Biozentrum, Mikrobiologie, Ludwig-Maximilians-Universität München, 82152 Martinsried, Germany; (T.H.); (T.B.); (Y.K.L.); (D.W.)
| | - Dina Weydert
- Biozentrum, Mikrobiologie, Ludwig-Maximilians-Universität München, 82152 Martinsried, Germany; (T.H.); (T.B.); (Y.K.L.); (D.W.)
| | - Andreas Brachmann
- Biozentrum, Genetik, Ludwig-Maximilians-Universität München, 82152 Martinsried, Germany;
| | - Heinrich Jung
- Biozentrum, Mikrobiologie, Ludwig-Maximilians-Universität München, 82152 Martinsried, Germany; (T.H.); (T.B.); (Y.K.L.); (D.W.)
- Correspondence:
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12
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Yao X, Tao F, Tang H, Hu H, Wang W, Xu P. Unique regulator SrpR mediates crosstalk between efflux pumps TtgABC and SrpABC in Pseudomonas putida B6-2 (DSM 28064). Mol Microbiol 2020; 115:131-141. [PMID: 32945019 DOI: 10.1111/mmi.14605] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 09/03/2020] [Accepted: 09/07/2020] [Indexed: 11/28/2022]
Abstract
The coexistence of multiple homologous resistance-nodulation-division (RND) efflux pumps in bacteria is frequently described with overlapping substrate profiles. However, it is unclear how bacteria balance their transcription in response to the changing environment. Here, we characterized a repressor, SrpR, in Pseudomonas putida B6-2 (DSM 28064), whose coding gene is adjacent to srpS that encodes the local repressor of the RND-type efflux pump SrpABC gene cluster. SrpR was demonstrated as a specific repressor of another RND efflux pump gene cluster ttgABC that is locally repressed by TtgR. SrpR was found to be capable of binding to the ttgABC operator with a higher affinity (KD , 138.0 nM) compared to TtgR (KD , 15.4 μM). EMSA and β-galactosidase assays were performed to survey possible effectors of SrpR with 35 available chemicals being tested. Only 2,3,4-trichlorophenol was identified as an effector of SrpR. A regulation model was then proposed, representing a novel strategy for balancing the efflux systems with partially overlapping substrate profiles. This study highlights sophisticated interactions among the RND efflux pumps in a Pseudomonas strain, which may endow bacteria with certain advantages in a fluctuant environment.
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Affiliation(s)
- Xuemei Yao
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, and School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China.,School of Chemistry and Life Sciences, Suzhou University of Science and Technology, Suzhou, People's Republic of China
| | - Fei Tao
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, and School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China
| | - Hongzhi Tang
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, and School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China
| | - Haiyang Hu
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, and School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China
| | - Weiwei Wang
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, and School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China
| | - Ping Xu
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, and School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China
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Sommer LM, Johansen HK, Molin S. Antibiotic resistance in Pseudomonas aeruginosa and adaptation to complex dynamic environments. Microb Genom 2020; 6:e000370. [PMID: 32375975 PMCID: PMC7371113 DOI: 10.1099/mgen.0.000370] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 04/02/2020] [Indexed: 12/12/2022] Open
Abstract
Antibiotic resistance has become a serious threat to human health (WHO Antibacterial Agents in Clinical Development: an Analysis of the Antibacterial Clinical Development Pipeline, Including Tuberculosis. Geneva: World Health Organization; 2017), and the ability to predict antibiotic resistance from genome sequencing has become a focal point for the medical community. With this genocentric prediction in mind, we were intrigued about two particular findings for a collection of clinical Pseudomonas aeruginosa isolates (Marvig et al. Nature Genetics 2015;47:57-64; Frimodt-Møller et al. Scientific Reports 2018;8:12512; Bartell et al. Nature Communications 2019;10:629): (i) 15 out of 52 genes found to be frequently targeted by adaptive mutations during the initial infection stage of cystic fibrosis airways ('candidate pathoadaptive genes') (Marvig et al. Nature Genetics 2015;47:57-64) were associated with antibiotic resistance (López-Causapé et al. Fronters in Microbiology 2018;9:685; López-Causapé et al. Antimicrobal Agents and Chemotherapy 2018;62:e02583-17); (ii) there was a parallel lack of resistance development and linkage to the genetic changes in these antibiotic-resistance-associated genes (Frimodt-Møller et al. Scientific Reports 2018;8:12512; Bartell et al. Nature Communications 2019;10:629). In this review, we highlight alternative selective forces that potentially enhance the infection success of P. aeruginosa and focus on the linkage to the 15 pathoadaptive antibiotic-resistance-associated genes, thereby showing the problems we may face when using only genomic information to predict and inform about relevant antibiotic treatment.
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Affiliation(s)
- Lea M. Sommer
- Department of Clinical Microbiology, Rigshospitalet, 2100 Copenhagen Ø, Denmark
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
| | - Helle K. Johansen
- Department of Clinical Microbiology, Rigshospitalet, 2100 Copenhagen Ø, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Søren Molin
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
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Kawalek A, Kotecka K, Modrzejewska M, Gawor J, Jagura-Burdzy G, Bartosik AA. Genome sequence of Pseudomonas aeruginosa PAO1161, a PAO1 derivative with the ICEPae1161 integrative and conjugative element. BMC Genomics 2020; 21:14. [PMID: 31906858 PMCID: PMC6945700 DOI: 10.1186/s12864-019-6378-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 12/08/2019] [Indexed: 12/20/2022] Open
Abstract
Background Pseudomonas aeruginosa is a cause of nosocomial infections, especially in patients with cystic fibrosis and burn wounds. PAO1 strain and its derivatives are widely used to study the biology of this bacterium, however recent studies demonstrated differences in the genomes and phenotypes of derivatives from different laboratories. Results Here we report the genome sequence of P. aeruginosa PAO1161 laboratory strain, a leu-, RifR, restriction-modification defective PAO1 derivative, described as the host of IncP-8 plasmid FP2, conferring the resistance to mercury. Comparison of PAO1161 genome with PAO1-UW sequence revealed lack of an inversion of a large genome segment between rRNA operons and 100 nucleotide polymorphisms, short insertions and deletions. These included a change in leuA, resulting in E108K substitution, which caused leucine auxotrophy and a mutation in rpoB, likely responsible for the rifampicin resistance. Nonsense mutations were detected in PA2735 and PA1939 encoding a DNA methyltransferase and a putative OLD family endonuclease, respectively. Analysis of revertants in these two genes showed that PA2735 is a component of a restriction-modification system, independent of PA1939. Moreover, a 12 kb RPG42 prophage and a novel 108 kb PAPI-1 like integrative conjugative element (ICE) encompassing a mercury resistance operon were identified. The ICEPae1161 was transferred to Pseudomonas putida cells, where it integrated in the genome and conferred the mercury resistance. Conclusions The high-quality P. aeruginosa PAO1161 genome sequence provides a reference for further research including e.g. investigation of horizontal gene transfer or comparative genomics. The strain was found to carry ICEPae1161, a functional PAPI-1 family integrative conjugative element, containing loci conferring mercury resistance, in the past attributed to the FP2 plasmid of IncP-8 incompatibility group. This indicates that the only known member of IncP-8 is in fact an ICE.
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Affiliation(s)
- Adam Kawalek
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Department of Microbial Biochemistry, Warsaw, Poland.
| | - Karolina Kotecka
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Department of Microbial Biochemistry, Warsaw, Poland
| | - Magdalena Modrzejewska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Department of Microbial Biochemistry, Warsaw, Poland
| | - Jan Gawor
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, DNA Sequencing and Oligonucleotide Synthesis Laboratory, Warsaw, Poland
| | - Grazyna Jagura-Burdzy
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Department of Microbial Biochemistry, Warsaw, Poland
| | - Aneta Agnieszka Bartosik
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Department of Microbial Biochemistry, Warsaw, Poland.
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Hill IT, Tallo T, Dorman MJ, Dove SL. Loss of RNA Chaperone Hfq Unveils a Toxic Pathway in Pseudomonas aeruginosa. J Bacteriol 2019; 201:e00232-19. [PMID: 31358608 PMCID: PMC6755729 DOI: 10.1128/jb.00232-19] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 07/22/2019] [Indexed: 12/17/2022] Open
Abstract
Hfq is an RNA chaperone that serves as a master regulator of bacterial physiology. Here we show that in the opportunistic pathogen Pseudomonas aeruginosa, the loss of Hfq can result in a dramatic reduction in growth in a manner that is dependent upon MexT, a transcription regulator that governs antibiotic resistance in this organism. Using a combination of chromatin immunoprecipitation with high-throughput sequencing and transposon insertion sequencing, we identify the MexT-activated genes responsible for mediating the growth defect of hfq mutant cells. These include a newly identified MexT-controlled gene that we call hilR We demonstrate that hilR encodes a small protein that is acutely toxic to wild-type cells when produced ectopically. Furthermore, we show that hilR expression is negatively regulated by Hfq, offering a possible explanation for the growth defect of hfq mutant cells. Finally, we present evidence that the expression of MexT-activated genes is dependent upon GshA, an enzyme involved in the synthesis of glutathione. Our findings suggest that Hfq can influence the growth of P. aeruginosa by limiting the toxic effects of specific MexT-regulated genes. Moreover, our results identify glutathione to be a factor important for the in vivo activity of MexT.IMPORTANCE Here we show that the conserved RNA chaperone Hfq is important for the growth of the opportunistic pathogen Pseudomonas aeruginosa We found that the growth defect of hfq mutant cells is dependent upon the expression of genes that are under the control of the transcription regulator MexT. These include a gene that we refer to as hilR, which we show is negatively regulated by Hfq and encodes a small protein that can be toxic when ectopically produced in wild-type cells. Thus, Hfq can influence the growth of P. aeruginosa by limiting the toxic effects of MexT-regulated genes, including one encoding a previously unrecognized small protein. We also show that MexT activity depends on an enzyme that synthesizes glutathione.
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Affiliation(s)
- Ian T Hill
- Division of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Thomas Tallo
- Division of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Matthew J Dorman
- Division of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Simon L Dove
- Division of Infectious Diseases, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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Draft Genome Sequences of Pseudomonas sp. Strains Isolated from Wheat in Germany. Microbiol Resour Announc 2019; 8:8/19/e00178-19. [PMID: 31072895 PMCID: PMC6509520 DOI: 10.1128/mra.00178-19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Three chloramphenicol-resistant Pseudomonas sp. strains were isolated from wheat grain in Germany on rose Bengal agar. The draft genome sizes ranged from 5,924,931 to 6,124,470 bp. Three chloramphenicol-resistant Pseudomonas sp. strains were isolated from wheat grain in Germany on rose Bengal agar. The draft genome sizes ranged from 5,924,931 to 6,124,470 bp. All the isolates possessed genes for efflux pumps that might be responsible for an intrinsic chloramphenicol resistance. No acquired antibiotic resistance genes in these strains could be determined.
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Haque S, Yadav DK, Bisht SC, Yadav N, Singh V, Dubey KK, Jawed A, Wahid M, Dar SA. Quorum sensing pathways in Gram-positive and -negative bacteria: potential of their interruption in abating drug resistance. J Chemother 2019; 31:161-187. [DOI: 10.1080/1120009x.2019.1599175] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Shafiul Haque
- Research and Scientific Studies Unit, College of Nursing and Allied Health Sciences, Jazan University, Jazan, Saudi Arabia
- Gene Expression Laboratory, Department of Biosciences, Faculty of Natural Sciences, Jamia Millia Islamia, New Delhi, India
| | - Dinesh K. Yadav
- Department of Botany, University of Allahabad, Allahabad, Uttar Pradesh, India
| | - Shekhar C. Bisht
- Department of Biotechnology, H.N.B Garhwal University, Srinagar, Uttarakhand, India
| | - Neelam Yadav
- Department of Botany, University of Allahabad, Allahabad, Uttar Pradesh, India
| | - Vineeta Singh
- Microbiology Division, CSIR-Central Drug Research Institute, Lucknow, Uttar Pradesh, India
| | - Kashyap Kumar Dubey
- Industrial Biotechnology Laboratory, University Institute of Engineering and Technology, M.D. University, Rohtak, Haryana, India
| | - Arshad Jawed
- Research and Scientific Studies Unit, College of Nursing and Allied Health Sciences, Jazan University, Jazan, Saudi Arabia
| | - Mohd Wahid
- Research and Scientific Studies Unit, College of Nursing and Allied Health Sciences, Jazan University, Jazan, Saudi Arabia
| | - Sajad Ahmad Dar
- Research and Scientific Studies Unit, College of Nursing and Allied Health Sciences, Jazan University, Jazan, Saudi Arabia
- Departments of Microbiology, University College of Medical Sciences (University of Delhi), Delhi, India
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Geng P, Leonard SP, Mishler DM, Barrick JE. Synthetic Genome Defenses against Selfish DNA Elements Stabilize Engineered Bacteria against Evolutionary Failure. ACS Synth Biol 2019; 8:521-531. [PMID: 30703321 DOI: 10.1021/acssynbio.8b00426] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Mobile genetic elements drive evolution by disrupting genes and rearranging genomes. Eukaryotes have evolved epigenetic mechanisms, including DNA methylation and RNA interference, that silence mobile elements and thereby preserve the integrity of their genomes. We created an artificial reprogrammable epigenetic system based on CRISPR interference to give engineered bacteria a similar line of defense against transposons and other selfish elements in their genomes. We demonstrate that this CRISPR interference against mobile elements (CRISPRi-ME) approach can be used to simultaneously repress two different transposon families in Escherichia coli, thereby increasing the evolutionary stability of costly protein expression. We further show that silencing a transposon in Acinetobacter baylyi ADP1 reduces mutation rates by a factor of 5, nearly as much as deleting all copies of this element from its genome. By deploying CRISPRi-ME on a broad-host-range vector, we have created a generalizable platform for stabilizing the genomes of engineered bacterial cells for applications in metabolic engineering and synthetic biology.
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Affiliation(s)
- Peng Geng
- Department of Molecular Biosciences, Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Sean P. Leonard
- Department of Molecular Biosciences, Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Dennis M. Mishler
- Department of Molecular Biosciences, Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Jeffrey E. Barrick
- Department of Molecular Biosciences, Center for Systems and Synthetic Biology, The University of Texas at Austin, Austin, Texas 78712, United States
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Serra C, Bouharkat B, Tir Touil-Meddah A, Guénin S, Mullié C. MexXY Multidrug Efflux System Is More Frequently Overexpressed in Ciprofloxacin Resistant French Clinical Isolates Compared to Hospital Environment Ones. Front Microbiol 2019; 10:366. [PMID: 30863391 PMCID: PMC6399115 DOI: 10.3389/fmicb.2019.00366] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 02/12/2019] [Indexed: 12/23/2022] Open
Abstract
Modulation of the membrane permeability through a decrease in porin-mediated antibiotic entry and/or an increase in antibiotic efflux is one of the resistance mechanisms to antibiotics evolved by Gram-negative bacteria. To assess whether the outer membrane porin OprD and Resistance-Nodulation-Division (RND) efflux pumps were similarly expressed in 33 ciprofloxacin-resistant clinical strains of Pseudomonas aeruginosa and in 30 non-clinical strains originating from the hospital environment (mainly waterborne Pseudomonas aeruginosa), the expression of oprD, mexB, mexF, and mexY genes was investigated. Overall, the expression of oprD was not detected by RT-qPCR in 14 (22%) strains and underexpressed in 35 (56%) more. No significant difference in oprD expression was detected between clinical and non-clinical strains. As for efflux pumps, 23 (70%) of the clinical strains overexpressed at least one of the tested RND genes. Overexpression of mexB, mexF and mexY was detected in 27, 12, and 45% of the clinical strains, respectively. In the 30 non-clinical strains, no overexpression could be found for mexB, mexF, or mexY. On the contrary, a global underexpression of the tested efflux pump genes was recorded. In both clinical and environmental strains, a positive correlation was found between the expressions of oprD and mexB. Similarly, the expressions of oprD and mexF were positively correlated. This result contrasts with the inverse correlation between both MexAB-OprM/MexEF-OprN and OprD previously described in carbapenem-resistant P. aeruginosa strains. The only positive correlation between phenotypic ciprofloxacin minimum inhibitory concentrations (MICs) and the expression of efflux pump gene was witnessed with mexY (analysis on pooled results for clinical and environmental strains). However, in clinical strains, no statistically significant link could be found between the degree of reduction in ciprofloxacin MICs witnessed with Phenylalanine-Arginine β-naphthylamide (PAβN) and the expression of any of the 3 RND genes tested.
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Affiliation(s)
- Cristiano Serra
- Laboratoire des Agents Infectieux, Resistance et Chimiothérapie - EA 4294, UFR de Pharmacie, Université de Picardie Jules Verne, Amiens, France
| | - Bakhta Bouharkat
- Laboratoire de Bioconversion, Génie Microbiologique et Sécurité Sanitaire N°145, Faculté des Sciences de la Nature et de la Vie, Université Mustapha Stambouli, Mascara, Algeria
| | - Aicha Tir Touil-Meddah
- Laboratoire de Bioconversion, Génie Microbiologique et Sécurité Sanitaire N°145, Faculté des Sciences de la Nature et de la Vie, Université Mustapha Stambouli, Mascara, Algeria
| | - Stéphanie Guénin
- Centre de Ressources Régionales en Biologie Moléculaire, UFR des Sciences, Université de Picardie Jules Verne, Amiens, France
| | - Catherine Mullié
- Laboratoire des Agents Infectieux, Resistance et Chimiothérapie - EA 4294, UFR de Pharmacie, Université de Picardie Jules Verne, Amiens, France.,Laboratoire d'Hygiène Hospitalière, Centre Hospitalier Universitaire Amiens-Picardie, Amiens, France
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Horna G, López M, Guerra H, Saénz Y, Ruiz J. Interplay between MexAB-OprM and MexEF-OprN in clinical isolates of Pseudomonas aeruginosa. Sci Rep 2018; 8:16463. [PMID: 30405166 PMCID: PMC6220265 DOI: 10.1038/s41598-018-34694-z] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 10/24/2018] [Indexed: 01/31/2023] Open
Abstract
MexAB-OprM and MexEF-OprN are Pseudomonas aeruginosa efflux pumps involved in the development of antibiotic resistance. Several studies developed with laboratory strains or using a few clinical isolates have reported that the regulation system of MexEF-OprN is involved in the final levels of MexAB-OprM expression. Therefore, this study was aimed to determine the interplay between MexAB-OprM and MexEF-OprN in 90 out of 190 P. aeruginosa clinical isolates with an efflux pump overexpression phenotype. Regarding oprD, 33% (30/90) of isolates displayed relevant modifications (RM) defined as frameshift or premature stop, both related to carbapenem resistance. On the other hand, 33% of the isolates displayed RM in nalC, nalD or mexR, which were significantly associated with multidrug resistance (MDR), non-susceptibility to carbapenems, OprD alterations and strong biofilm production. Meanwhile, the RM in MexS were associated with presence of pigment (p = 0.004). Otherwise, when all the regulators were analysed together, the association between RM in MexAB-OprM regulators and MDR was only significant (p = 0.039) when mexS was the wild type. These data show the modulatory effect of MexEF-OprN on MexAB-OprM in a clinical population of P. aeruginosa. Further studies may contribute to design of novel molecules acting on this interplay to fight against antimicrobial resistance.
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Affiliation(s)
- Gertrudis Horna
- Barcelona Institute for Global Health, ISGlobal, Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
- Universidad Peruana Cayetano Heredia, Instituto de Medicina Tropical Alexander von Humboldt, Lima, Peru
| | - María López
- Área de Microbiología Molecular, Centro de Investigación Biomédica de La Rioja (CIBIR), Logroño, Spain
| | - Humberto Guerra
- Universidad Peruana Cayetano Heredia, Instituto de Medicina Tropical Alexander von Humboldt, Lima, Peru
| | - Yolanda Saénz
- Área de Microbiología Molecular, Centro de Investigación Biomédica de La Rioja (CIBIR), Logroño, Spain
| | - Joaquim Ruiz
- Barcelona Institute for Global Health, ISGlobal, Hospital Clínic - Universitat de Barcelona, Barcelona, Spain.
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Dhar S, Kumari H, Balasubramanian D, Mathee K. Cell-wall recycling and synthesis in Escherichia coli and Pseudomonas aeruginosa – their role in the development of resistance. J Med Microbiol 2018; 67:1-21. [DOI: 10.1099/jmm.0.000636] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Affiliation(s)
- Supurna Dhar
- Department of Human and Molecular Genetics, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Hansi Kumari
- Department of Human and Molecular Genetics, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | | | - Kalai Mathee
- Biomolecular Sciences Institute, Florida International University, Miami, FL, USA
- Department of Human and Molecular Genetics, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
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22
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Singh M, Yau YCW, Wang S, Waters V, Kumar A. MexXY efflux pump overexpression and aminoglycoside resistance in cystic fibrosis isolates of Pseudomonas aeruginosa from chronic infections. Can J Microbiol 2017; 63:929-938. [PMID: 28922614 DOI: 10.1139/cjm-2017-0380] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In this study, we analyzed 15 multidrug-resistant cystic fibrosis isolates of Pseudomonas aeruginosa from chronic lung infections for expression of 4 different multidrug efflux systems (MexAB-OprM, MexCD-OprJ, MexEF-OprN, and MexXY), using quantitative reverse transcriptase PCR. Overexpression of MexXY pump was observed in all of the isolates tested. Analysis of regulatory genes that control the expression of these 4 efflux pumps revealed a number of previously uncharacterized mutations. Our work shows that MexXY pump overexpression is common in cystic fibrosis isolates and could be contributing to their reduced aminoglycoside susceptibility. Further, we also identified novel mutations in the regulatory genes of the 4 abovementioned Resistance-Nodulation-Division superfamily pumps that may be involved in the overexpression of these pumps.
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Affiliation(s)
- Manu Singh
- a Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Yvonne C W Yau
- b Division of Microbiology, Department of Paediatric Laboratory Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Shirley Wang
- a Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Valerie Waters
- c Division of Infectious Diseases, Department of Paediatrics, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Ayush Kumar
- a Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada.,d Manitoba Chemosensory Biology Group, University of Manitoba, Winnipeg, Manitoba, Canada
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Sidorenko J, Jatsenko T, Kivisaar M. Ongoing evolution of Pseudomonas aeruginosa PAO1 sublines complicates studies of DNA damage repair and tolerance. Mutat Res 2017; 797-799:26-37. [PMID: 28340408 DOI: 10.1016/j.mrfmmm.2017.03.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 12/23/2016] [Accepted: 03/07/2017] [Indexed: 06/06/2023]
Abstract
Sublines of the major P. aeruginosa reference strain PAO1 are derivatives of the original PAO1 isolate, which are maintained in laboratories worldwide. These sublines display substantial genomic and phenotypic variation due to ongoing microevolution. Here, we examined four sublines, MPAO1, PAO1-L, PAO1-DSM and PAO1-UT, originated from different laboratories, and six DNA polymerase-deficient mutants from the P. aeruginosa MPAO1 transposon library for their employment in elucidation of DNA damage repair and tolerance mechanisms in P. aeruginosa. We found that PAO1 subline PAO1-UT carries a large deletion encompassing the DNA damage inducible imuA-imuB-imuC cassette (PA0669-PA0671), which is implied in mutagenesis in several species. Furthermore, the genetic changes leading to variation in the functionality of the MexEF-OprN efflux system contributed largely to the phenotypic discordance between P. aeruginosa PAO1 sublines. Specifically, we identified multiple mutations in the mexT gene, which encodes a transcriptional regulator of the mexEF-oprN genes, mutations in the mexF, and complete absence of these genes. Of the four tested sublines, MPAO1 was the only subline with the functional MexEF-OprN multidrug efflux system. Active efflux through MexEF-OprN rendered MPAO1 highly resistant to chloramphenicol and ciprofloxacin. Moreover, the functions of specialized DNA polymerase IV and nucleotide excision repair (NER) in 4-NQO-induced DNA damage tolerance appeared to be masked in MPAO1, while were easily detectable in other sublines. Finally, the frequencies of spontaneous and MMS-induced Rifr mutations were also significantly lower in MPAO1 in comparison to the PAO1 sublines with impaired MexEF-OprN efflux system. The MexEF-OprN-attributed differences were also observed between MPAO1 and MPAO1-derived transposon mutants from the two-allele transposon mutant collection. Thus, the accumulating mutations and discordant phenotypes of the PAO1 derivatives challenge the reproducibility and comparability of the results obtained with different PAO1 sublines and also limit the usage of the MPAO1 transposon library in DNA damage tolerance and mutagenesis studies.
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Affiliation(s)
- Julia Sidorenko
- Department of Genetics, Institute of Molecular and Cell Biology, University of Tartu, 23 Riia Street, 51010, Tartu, Estonia.
| | - Tatjana Jatsenko
- Department of Genetics, Institute of Molecular and Cell Biology, University of Tartu, 23 Riia Street, 51010, Tartu, Estonia
| | - Maia Kivisaar
- Department of Genetics, Institute of Molecular and Cell Biology, University of Tartu, 23 Riia Street, 51010, Tartu, Estonia.
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Stability of the GraA Antitoxin Depends on Growth Phase, ATP Level, and Global Regulator MexT. J Bacteriol 2015; 198:787-96. [PMID: 26668267 DOI: 10.1128/jb.00684-15] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Accepted: 12/10/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Bacterial type II toxin-antitoxin systems consist of a potentially poisonous toxin and an antitoxin that inactivates the toxic protein by binding to it. Most of the toxins regulate stress survival, but their activation depends on the stability of the antitoxin that has to be degraded in order for the toxin to be able to attack its cellular targets. The degradation of antitoxins is usually rapid and carried out by ATP-dependent protease Lon or Clp, which is activated under stress conditions. The graTA system of Pseudomonas putida encodes the toxin GraT, which can affect the growth rate and stress tolerance of bacteria but is under most conditions inactivated by the unusually stable antitoxin GraA. Here, we aimed to describe the stability features of the antitoxin GraA by analyzing its degradation rate in total cell lysates of P. putida. We show that the degradation rate of GraA depends on the growth phase of bacteria being fastest in the transition from exponential to stationary phase. In accordance with this, higher ATP levels were shown to stabilize GraA. Differently from other antitoxins, the main cellular proteases Lon and Clp are not involved in GraA stability. Instead, GraA seems to be degraded through a unique pathway involving an endoprotease that cleaves the antitoxin into two unequal parts. We also identified the global transcriptional regulator MexT as a factor for destabilization of GraA, which indicates that the degradation of GraA may be induced by conditions similar to those that activate MexT. IMPORTANCE Toxin-antitoxin (TA) modules are widespread in bacterial chromosomes and have important roles in stress tolerance. As activation of a type II toxin is triggered by proteolytic degradation of the antitoxin, knowledge about the regulation of the antitoxin stability is critical for understanding the activation of a particular TA module. Here, we report on the unusual degradation pathway of the antitoxin GraA of the recently characterized GraTA system. While GraA is uncommonly stable in the exponential and late-stationary phases, its degradation increases in the transition phase. The degradation pathway of GraA involves neither Lon nor Clp, which usually targets antitoxins, but rather an unknown endoprotease and the global regulator MexT, suggesting a new type of regulation of antitoxin stability.
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Complete Genome Sequence of Pseudomonas aeruginosa Strain 8380, Isolated from the Human Gut. GENOME ANNOUNCEMENTS 2015; 3:3/3/e00520-15. [PMID: 25999558 PMCID: PMC4440972 DOI: 10.1128/genomea.00520-15] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Pseudomonas aeruginosa shows multidrug resistance, which is mainly attributable to its expression of xenobiotic efflux pumps. However, it is unclear how silent pumps are expressed in clinical isolates. Here, we sequenced the complete genome of P. aeruginosa strain 8380, which was isolated from a human gut.
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Li XZ, Plésiat P, Nikaido H. The challenge of efflux-mediated antibiotic resistance in Gram-negative bacteria. Clin Microbiol Rev 2015; 28:337-418. [PMID: 25788514 PMCID: PMC4402952 DOI: 10.1128/cmr.00117-14] [Citation(s) in RCA: 899] [Impact Index Per Article: 99.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The global emergence of multidrug-resistant Gram-negative bacteria is a growing threat to antibiotic therapy. The chromosomally encoded drug efflux mechanisms that are ubiquitous in these bacteria greatly contribute to antibiotic resistance and present a major challenge for antibiotic development. Multidrug pumps, particularly those represented by the clinically relevant AcrAB-TolC and Mex pumps of the resistance-nodulation-division (RND) superfamily, not only mediate intrinsic and acquired multidrug resistance (MDR) but also are involved in other functions, including the bacterial stress response and pathogenicity. Additionally, efflux pumps interact synergistically with other resistance mechanisms (e.g., with the outer membrane permeability barrier) to increase resistance levels. Since the discovery of RND pumps in the early 1990s, remarkable scientific and technological advances have allowed for an in-depth understanding of the structural and biochemical basis, substrate profiles, molecular regulation, and inhibition of MDR pumps. However, the development of clinically useful efflux pump inhibitors and/or new antibiotics that can bypass pump effects continues to be a challenge. Plasmid-borne efflux pump genes (including those for RND pumps) have increasingly been identified. This article highlights the recent progress obtained for organisms of clinical significance, together with methodological considerations for the characterization of MDR pumps.
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Affiliation(s)
- Xian-Zhi Li
- Human Safety Division, Veterinary Drugs Directorate, Health Products and Food Branch, Health Canada, Ottawa, Ontario, Canada
| | - Patrick Plésiat
- Laboratoire de Bactériologie, Faculté de Médecine-Pharmacie, Centre Hospitalier Régional Universitaire, Université de Franche-Comté, Besançon, France
| | - Hiroshi Nikaido
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
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Ding F, Lee KJ, Vahedi-Faridi A, Yoneyama H, Osgood CJ, Xu XHN. Design and study of the efflux function of the EGFP fused MexAB-OprM membrane transporter in Pseudomonas aeruginosa using fluorescence spectroscopy. Analyst 2014; 139:3088-96. [PMID: 24781334 DOI: 10.1039/c4an00108g] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Multidrug membrane transporters (efflux pumps) can selectively extrude a variety of structurally and functionally diverse substrates (e.g., chemotoxics, antibiotics), leading to multidrug resistance (MDR) and ineffective treatment of a wide variety of diseases. In this study, we have designed and constructed a fusion gene (egfp-mexB) of N-terminal mexB with C-terminal egfp, inserted it into a plasmid vector (pMMB67EH), and successfully expressed it in the ΔMexB (MexB deletion) strain of Pseudomonas aeruginosa to create a new strain that expresses MexA-(EGFP-MexB)-OprM. We characterized the fusion gene using gel electrophoresis and DNA sequencing, and determined its expression in live cells by measuring the fluorescence of EGFP in single live cells using fluorescence microscopy. Efflux function of the new strain was studied by measuring its accumulation kinetics of ethidium bromide (EtBr, a pump substrate) using fluorescence spectroscopy, which was compared with cells (WT, ΔMexM, ΔABM, and nalB1) with various expression levels of MexAB-OprM. The new strain shows 6-fold lower accumulation rates of EtBr (15 μM) than ΔABM, 4-fold lower than ΔMexB, but only 1.1-fold higher than WT. As the EtBr concentration increases to 40 μM, the new strain has nearly the same accumulation rate of EtBr as ΔMexB, but 1.4-fold higher than WT. We observed the nearly same level of inhibitory effect of CCCP (carbonyl cyanide-m-chlorophenylhydrazone) on the efflux of EtBr by the new strain and WT. Antibiotic susceptibility study shows that the minimum inhibitory concentrations (MICs) of aztreonam (AZT) and chloramphenicol (CP) for the new strain are 6-fold or 3-fold lower than WT, respectively, and 2-fold higher than those of ΔMexB. Taken together, the results suggest that the fusion protein partially retains the efflux function of MexAB-OprM. The modeled structure of the fusion protein shows that the position and orientation of the N-terminal fused EGFP domain may either partially block the translocation pore or restrict the movement of the individual pump domains, which may lead to partially restricted efflux activity.
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Affiliation(s)
- Feng Ding
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529, USA.
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