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Yaeger LN, Ranieri MRM, Chee J, Karabelas-Pittman S, Rudolph M, Giovannoni AM, Harvey H, Burrows LL. A genetic screen identifies a role for oprF in Pseudomonas aeruginosa biofilm stimulation by subinhibitory antibiotics. NPJ Biofilms Microbiomes 2024; 10:30. [PMID: 38521769 PMCID: PMC10960818 DOI: 10.1038/s41522-024-00496-7] [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: 09/06/2023] [Accepted: 03/05/2024] [Indexed: 03/25/2024] Open
Abstract
Biofilms are surface-associated communities of bacteria that grow in a self-produced matrix of polysaccharides, proteins, and extracellular DNA (eDNA). Sub-minimal inhibitory concentrations (sub-MIC) of antibiotics induce biofilm formation, potentially as a defensive response to antibiotic stress. However, the mechanisms behind sub-MIC antibiotic-induced biofilm formation are unclear. We show that treatment of Pseudomonas aeruginosa with multiple classes of sub-MIC antibiotics with distinct targets induces biofilm formation. Further, addition of exogenous eDNA or cell lysate failed to increase biofilm formation to the same extent as antibiotics, suggesting that the release of cellular contents by antibiotic-driven bacteriolysis is insufficient. Using a genetic screen for stimulation-deficient mutants, we identified the outer membrane porin OprF and the ECF sigma factor SigX as important. Similarly, loss of OmpA - the Escherichia coli OprF homolog - prevented sub-MIC antibiotic stimulation of E. coli biofilms. Our screen also identified the periplasmic disulfide bond-forming enzyme DsbA and a predicted cyclic-di-GMP phosphodiesterase encoded by PA2200 as essential for biofilm stimulation. The phosphodiesterase activity of PA2200 is likely controlled by a disulfide bond in its regulatory domain, and folding of OprF is influenced by disulfide bond formation, connecting the mutant phenotypes. Addition of reducing agent dithiothreitol prevented sub-MIC antibiotic biofilm stimulation. Finally, activation of a c-di-GMP-responsive promoter follows treatment with sub-MIC antibiotics in the wild-type but not an oprF mutant. Together, these results show that antibiotic-induced biofilm formation is likely driven by a signaling pathway that translates changes in periplasmic redox state into elevated biofilm formation through increases in c-di-GMP.
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Affiliation(s)
- Luke N Yaeger
- Biochemistry and Biomedical Sciences and the Michael G. DeGroote Centre for Infectious Disease Research, McMaster University, Hamilton, ON, Canada
| | - Michael R M Ranieri
- Biochemistry and Biomedical Sciences and the Michael G. DeGroote Centre for Infectious Disease Research, McMaster University, Hamilton, ON, Canada
| | - Jessica Chee
- Biochemistry and Biomedical Sciences and the Michael G. DeGroote Centre for Infectious Disease Research, McMaster University, Hamilton, ON, Canada
| | - Sawyer Karabelas-Pittman
- Biochemistry and Biomedical Sciences and the Michael G. DeGroote Centre for Infectious Disease Research, McMaster University, Hamilton, ON, Canada
| | - Madeleine Rudolph
- Biochemistry and Biomedical Sciences and the Michael G. DeGroote Centre for Infectious Disease Research, McMaster University, Hamilton, ON, Canada
| | - Alessio M Giovannoni
- Biochemistry and Biomedical Sciences and the Michael G. DeGroote Centre for Infectious Disease Research, McMaster University, Hamilton, ON, Canada
| | - Hanjeong Harvey
- Biochemistry and Biomedical Sciences and the Michael G. DeGroote Centre for Infectious Disease Research, McMaster University, Hamilton, ON, Canada
| | - Lori L Burrows
- Biochemistry and Biomedical Sciences and the Michael G. DeGroote Centre for Infectious Disease Research, McMaster University, Hamilton, ON, Canada.
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Zhao Y, Wee CY, Zhang H, Yang Z, Wang WEJ, Thian ES. Silver-substituted hydroxyapatite inhibits Pseudomonas aeruginosa outer membrane protein F: A potential antibacterial mechanism. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2022; 134:112713. [DOI: 10.1016/j.msec.2022.112713] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 01/06/2022] [Accepted: 02/09/2022] [Indexed: 12/20/2022]
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The Landscape of Pseudomonas aeruginosa Membrane-Associated Proteins. Cells 2020; 9:cells9112421. [PMID: 33167383 PMCID: PMC7694347 DOI: 10.3390/cells9112421] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 10/29/2020] [Accepted: 11/01/2020] [Indexed: 12/15/2022] Open
Abstract
Background: Pseudomonas aeruginosa cell envelope-associated proteins play a relevant role in infection mechanisms. They can contribute to the antibiotic resistance of the bacterial cells and be involved in the interaction with host cells. Thus, studies contributing to elucidating these key molecular elements are of great importance to find alternative therapeutics. Methods: Proteins and peptides were extracted by different methods and analyzed by Multidimensional Protein Identification Technology (MudPIT) approach. Proteomic data were processed by Discoverer2.1 software and multivariate statistics, i.e., Linear Discriminant Analysis (LDA), while the Immune Epitope Database (IEDB) resources were used to predict antigenicity and immunogenicity of experimental identified peptides and proteins. Results: The combination of 29 MudPIT runs allowed the identification of 10,611 peptides and 2539 distinct proteins. Following application of extraction methods enriching specific protein domains, about 15% of total identified peptides were classified in trans inner-membrane, inner-membrane exposed, trans outer-membrane and outer-membrane exposed. In this scenario, nine outer membrane proteins (OprE, OprI, OprF, OprD, PagL, OprG, PA1053, PAL and PA0833) were predicted to be highly antigenic. Thus, they were further processed and epitopes target of T cells (MHC Class I and Class II) and B cells were predicted. Conclusion: The present study represents one of the widest characterizations of the P. aeruginosa membrane-associated proteome. The feasibility of our method may facilitates the investigation of other bacterial species whose envelope exposed protein domains are still unknown. Besides, the stepwise prioritization of proteome, by combining experimental proteomic data and reverse vaccinology, may be useful for reducing the number of proteins to be tested in vaccine development.
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Baral B, Mozafari MR. Strategic Moves of "Superbugs" Against Available Chemical Scaffolds: Signaling, Regulation, and Challenges. ACS Pharmacol Transl Sci 2020; 3:373-400. [PMID: 32566906 PMCID: PMC7296549 DOI: 10.1021/acsptsci.0c00005] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2020] [Indexed: 12/12/2022]
Abstract
Superbugs' resistivity against available natural products has become an alarming global threat, causing a rapid deterioration in public health and claiming tens of thousands of lives yearly. Although the rapid discovery of small molecules from plant and microbial origin with enhanced bioactivity has provided us with some hope, a rapid hike in the resistivity of superbugs has proven to be the biggest therapeutic hurdle of all times. Moreover, several distinct mechanisms endowed by these notorious superbugs make them immune to these antibiotics subsequently causing our antibiotic wardrobe to be obsolete. In this unfortunate situation, though the time frame for discovering novel "hit molecules" down the line remains largely unknown, our small hope and untiring efforts injected in hunting novel chemical scaffolds with unique molecular targets using high-throughput technologies may safeguard us against these life-threatening challenges to some extent. Amid this crisis, the current comprehensive review highlights the present status of knowledge, our search for bacteria Achilles' heel, distinct molecular signaling that an opportunistic pathogen bestows to trespass the toxicity of antibiotics, and facile strategies and appealing therapeutic targets of novel drugs. Herein, we also discuss multidimensional strategies to combat antimicrobial resistance.
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Affiliation(s)
- Bikash Baral
- Department
of Biochemistry, University of Turku, Tykistökatu 6, Turku, Finland
| | - M. R. Mozafari
- Australasian
Nanoscience and Nanotechnology Initiative, 8054 Monash University LPO, Clayton, Victoria 3168, Australia
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Geisinger E, Huo W, Hernandez-Bird J, Isberg RR. Acinetobacter baumannii: Envelope Determinants That Control Drug Resistance, Virulence, and Surface Variability. Annu Rev Microbiol 2019; 73:481-506. [DOI: 10.1146/annurev-micro-020518-115714] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Acinetobacter baumannii has emerged as an important nosocomial pathogen, particularly for patients in intensive care units and with invasive indwelling devices. The most recent clinical isolates are resistant to several classes of clinically important antibiotics, greatly restricting the ability to effectively treat critically ill patients. The bacterial envelope is an important driver of A. baumannii disease, both at the level of battling against antibiotic therapy and at the level of protecting from host innate immune function. This review provides a comprehensive overview of key features of the envelope that interface with both the host and antimicrobial therapies. Carbohydrate structures that contribute to protecting from the host are detailed, and mutations that alter these structures, resulting in increased antimicrobial resistance, are explored. In addition, protein complexes involved in both intermicrobial and host-microbe interactions are described. Finally we discuss regulatory mechanisms that control the nature of the cell envelope and its impact on host innate immune function.
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Affiliation(s)
- Edward Geisinger
- Department of Biology, Northeastern University, Boston, Massachusetts 02115, USA
| | - Wenwen Huo
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
| | - Juan Hernandez-Bird
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
| | - Ralph R. Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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Dreier J, Ruggerone P. Interaction of antibacterial compounds with RND efflux pumps in Pseudomonas aeruginosa. Front Microbiol 2015; 6:660. [PMID: 26217310 PMCID: PMC4495556 DOI: 10.3389/fmicb.2015.00660] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 06/16/2015] [Indexed: 01/14/2023] Open
Abstract
Pseudomonas aeruginosa infections are becoming increasingly difficult to treat due to intrinsic antibiotic resistance and the propensity of this pathogen to accumulate diverse resistance mechanisms. Hyperexpression of efflux pumps of the Resistance-Nodulation-Cell Division (RND)-type multidrug efflux pumps (e.g., MexAB-OprM), chromosomally encoded by mexAB-oprM, mexCD-oprJ, mexEF-oprN, and mexXY (-oprA) is often detected in clinical isolates and contributes to worrying multi-drug resistance phenotypes. Not all antibiotics are affected to the same extent by the aforementioned RND efflux pumps. The impact of efflux on antibiotic activity varies not only between different classes of antibiotics but also between members of the same family of antibiotics. Subtle differences in physicochemical features of compound-pump and compound-solvent interactions largely determine how compounds are affected by efflux activity. The combination of different high-resolution techniques helps to gain insight into the functioning of these molecular machineries. This review discusses substrate recognition patterns based on experimental evidence and computer simulations with a focus on MexB, the pump subunit of the main RND transporter in P. aeruginosa.
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Affiliation(s)
- Jürg Dreier
- Basilea Pharmaceutica International Ltd.,Basel, Switzerland
| | - Paolo Ruggerone
- Dipartimento di Fisica, Università di Cagliari – Cittadella UniversitariaMonserrato, Italy
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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: 924] [Impact Index Per Article: 102.7] [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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Conformation-specific labeling of BamA and suppressor analysis suggest a cyclic mechanism for β-barrel assembly in Escherichia coli. Proc Natl Acad Sci U S A 2013; 110:5151-6. [PMID: 23479609 DOI: 10.1073/pnas.1302662110] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In gram-negative bacteria, integral outer membrane β-barrel proteins (OMPs) are assembled by the beta-barrel assembly machine (Bam) complex. The essential components of this complex are the OMP BamA [which contains a carboxyl-terminal β-barrel and an amino-terminal periplasmic module composed of five polypeptide transport associated (POTRA) domains] and the lipoprotein BamD. In Escherichia coli, the Bam complex also contains three nonessential lipoproteins (BamBCE), all of which require the barrel-proximal POTRA domain (P5) for stable interactions with BamA. We have previously reported that the BamA β-barrel assumes two different conformations. A method for conformation-specific labeling of BamA described here reveals that these conformers reflect the degree of surface exposure of the conserved sixth extracellular loop (L6). L6 is surface accessible in one conformation but not in the other, likely because it occupies the lumen of the BamA β-barrel in the latter case. A gain-of-function mutation that promotes Bam activity (bamDR197L) and a loss-of-function mutation that decreases the activity of Bam (ΔbamE) both favor surface exposure of BamA L6, suggesting that BamD and BamE normally act to control L6 exposure through opposing functions. These results, along with the synthetic lethality of the bamDR197L ΔbamE double mutant, imply a cyclic mechanism in which the Bam lipoproteins regulate the conformation of BamA during the OMP assembly reaction. Our results further suggest that BamDE controls L6 exposure via conformational signals transmitted through P5 to L6.
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Funken H, Bartels KM, Wilhelm S, Brocker M, Bott M, Bains M, Hancock REW, Rosenau F, Jaeger KE. Specific association of lectin LecB with the surface of Pseudomonas aeruginosa: role of outer membrane protein OprF. PLoS One 2012; 7:e46857. [PMID: 23056489 PMCID: PMC3466170 DOI: 10.1371/journal.pone.0046857] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 09/06/2012] [Indexed: 01/31/2023] Open
Abstract
The fucose binding lectin LecB affects biofilm formation and is involved in pathogenicity of Pseudomonas aeruginosa. LecB resides in the outer membrane and can be released specifically by treatment of an outer membrane fraction with fucose suggesting that it binds to specific ligands. Here, we report that LecB binds to the outer membrane protein OprF. In an OprF-deficient P. aeruginosa mutant, LecB is no longer detectable in the membrane but instead in the culture supernatant indicating a specific interaction between LecB and OprF.
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Affiliation(s)
- Horst Funken
- Institute of Molecular Enzyme Technology, Heinrich-Heine-University Duesseldorf, Juelich, Germany
| | - Kai-Malte Bartels
- Institute of Molecular Enzyme Technology, Heinrich-Heine-University Duesseldorf, Juelich, Germany
| | - Susanne Wilhelm
- Institute of Molecular Enzyme Technology, Heinrich-Heine-University Duesseldorf, Juelich, Germany
| | - Melanie Brocker
- Institute of Bio- and Geoscience 1, Forschungszentrum Jülich, Juelich, Germany
| | - Michael Bott
- Institute of Bio- and Geoscience 1, Forschungszentrum Jülich, Juelich, Germany
| | - Manjeet Bains
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada
| | - Robert E. W. Hancock
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada
| | - Frank Rosenau
- Institute of Pharmaceutical Biotechnology, Ulm-University, Ulm, Germany
| | - Karl-Erich Jaeger
- Institute of Molecular Enzyme Technology, Heinrich-Heine-University Duesseldorf, Juelich, Germany
- * E-mail:
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10
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Abstract
Acinetobacter species show high levels of intrinsic resistance to many antibiotics. The major protein species in the outer membrane of Acinetobacter baumannii does not belong to the high-permeability trimeric porin family, which includes Escherichia coli OmpF/OmpC, and instead is a close homolog of E. coli OmpA and Pseudomonas aeruginosa OprF. We characterized the pore-forming function of this OmpA homolog, OmpA(Ab), by a reconstitution assay. OmpA(Ab) produced very low pore-forming activity, about 70-fold lower than that of OmpF and an activity similar to that of E. coli OmpA and P. aeruginosa OprF. The pore size of the OmpA(Ab) channel was similar to that of OprF, i.e., about 2 nm in diameter. The low permeability of OmpA(Ab) is not due to the inactivation of this protein during purification, because the permeability of the whole A. baumannii outer membrane was also very low. Furthermore, the outer membrane permeability to cephalothin and cephaloridine, measured in intact cells, was about 100-fold lower than that of E. coli K-12. The permeability of cephalothin and cephaloridine in A. baumannii was decreased 2- to 3-fold when the ompA(Ab) gene was deleted. These results show that OmpA(Ab) is the major nonspecific channel in A. baumannii. The low permeability of this porin, together with the presence of constitutive β-lactamases and multidrug efflux pumps, such as AdeABC and AdeIJK, appears to be essential for the high levels of intrinsic resistance to a number of antibiotics.
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11
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Sugawara E, Nagano K, Nikaido H. Alternative folding pathways of the major porin OprF of Pseudomonas aeruginosa. FEBS J 2012; 279:910-8. [PMID: 22240095 DOI: 10.1111/j.1742-4658.2012.08481.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OprF is the major porin of Pseudomonas aeruginosa and allows very slow, nonspecific, diffusion of solutes. The low permeability of this porin channel is a major factor that enhances other types of resistance mechanisms and often creates strong multidrug resistance in this nosocomial pathogen. We have previously shown that the low permeability is caused by the folding of OprF into two conformers: a majority, two-domain closed-channel conformer containing the N-terminal transmembrane β-barrel and the C-terminal periplasmic, globular domain; and a minority, one-domain open-channel conformer comprising < 5% of the protein population. Our analysis of the bifurcate folding pathway using site-directed mutagenesis showed that slowing down the folding of the two-domain conformer increases the fraction of the open, one-domain conformer. Use of outer membrane protein assembly machinery mutants showed that the absence of the Skp chaperone led to an increased proportion of open conformers. As many environmental pathogens causing nosocomial infections appear to have outer membrane protein (OmpA)/OprF homologs as the major porin, efforts to understand the low permeability of these 'slow porins' are important in our fight against these organisms.
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Affiliation(s)
- Etsuko Sugawara
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
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Kazemi M, Kasra Kermanshahi R, Heshmat Dehkordi E, Payami F, Behjati M. Resistance index of penicillin-resistant bacteria to various physicochemical agents. ISRN MICROBIOLOGY 2012; 2012:789474. [PMID: 23724332 PMCID: PMC3658797 DOI: 10.5402/2012/789474] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/10/2011] [Accepted: 10/23/2011] [Indexed: 11/26/2022]
Abstract
Widespread use of various antimicrobial agents resulted in the emergence of bacterial resistance. Mechanisms like direct efflux, formation, and sequestration of metals and drugs in complexes and antiporter pumps are some examples. This investigation aims to investigate the resistance pattern of penicillin-resistant bacterial strains to some physicochemical agents. Sensitivity/resistance pattern of common bacterial strains to antimicrobial agents were evaluated by disk diffusion assay. Broth and agar dilution method were used for determination of minimum inhibitory concentration and minimal bactericidal concentration. The impact of UV ray on the bacterial growth under laminar flow hood was measured using photonmeter. Our data demonstrates that the most prevalent metal resistance was against arsenate (95.92%), followed by cadmium (52.04%) and mercury (36.73%). There was significant difference between cetrimide resistances among studied microbial strains especially for P. aeruginosa (P < 0.05). High rate of pathogen resistance to various antibacterial agents in our study supports previously published data. This great rate of bacterial resistance is attributed to the emergence of defense mechanisms developed in pathogens. The higher general bacterial resistance rate among Staphylococcus strains rather than E. coli and P. aeruginosa strains draws attention towards focusing on designing newer therapeutic compounds for Staphylococcus strains.
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Affiliation(s)
- M Kazemi
- Department of Genetics and Molecular Biology, Medical School, Isfahan University of Medical Sciences, Isfahan 81746-73461, Iran
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Nikaido H, Pagès JM. Broad-specificity efflux pumps and their role in multidrug resistance of Gram-negative bacteria. FEMS Microbiol Rev 2011; 36:340-63. [PMID: 21707670 DOI: 10.1111/j.1574-6976.2011.00290.x] [Citation(s) in RCA: 489] [Impact Index Per Article: 37.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Antibiotic resistance mechanisms reported in Gram-negative bacteria are causing a worldwide health problem. The continuous dissemination of 'multidrug-resistant' (MDR) bacteria drastically reduces the efficacy of our antibiotic 'arsenal' and consequently increases the frequency of therapeutic failure. In MDR bacteria, the overexpression of efflux pumps that expel structurally unrelated drugs contributes to the reduced susceptibility by decreasing the intracellular concentration of antibiotics. During the last decade, several clinical data have indicated an increasing involvement of efflux pumps in the emergence and dissemination of resistant Gram-negative bacteria. It is necessary to clearly define the molecular, functional and genetic bases of the efflux pump in order to understand the translocation of antibiotic molecules through the efflux transporter. The recent investigation on the efflux pump AcrB at its structural and physiological levels, including the identification of drug affinity sites and kinetic parameters for various antibiotics, may pave the way towards the rational development of an improved new generation of antibacterial agents as well as efflux inhibitors in order to efficiently combat efflux-based resistance mechanisms.
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Affiliation(s)
- Hiroshi Nikaido
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
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