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Seewald M, Nielinger L, Alker K, Behnke JS, Wycisk V, Urner LH. Detergent Chemistry Modulates the Transgression of Planetary Boundaries including Antimicrobial Resistance and Drug Discovery. Angew Chem Int Ed Engl 2024; 63:e202403833. [PMID: 38619211 DOI: 10.1002/anie.202403833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 03/13/2024] [Accepted: 03/13/2024] [Indexed: 04/16/2024]
Abstract
Detergent chemistry enables applications in the world today while harming safe operating spaces that humanity needs for survival. Aim of this review is to support a holistic thought process in the design of detergent chemistry. We harness the planetary boundary concept as a framework for literature survey to identify progresses and knowledge gaps in context with detergent chemistry and five planetary boundaries that are currently transgressed, i.e., climate, freshwater, land system, novel entities, biosphere integrity. Our survey unveils the status of three critical challenges to be addressed in the years to come, including (i) the implementation of a holistically, climate-friendly detergent industry; (ii) the alignment of materialistic and social aspects in creating technical solutions by means of sustainable chemistry; (iii) the development of detergents that serve the purpose of applications but do not harm the biosphere in their role as novel entities. Specifically, medically relevant case reports revealed that even the most sophisticated detergent design cannot sufficiently accelerate drug discovery to outperform the antibiotic resistance development that detergents simultaneously promote as novel entities. Safe operating spaces that humanity needs for its survival may be secured by directing future efforts beyond sustainable chemistry, resource efficiency, and net zero emission targets.
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Affiliation(s)
- Marc Seewald
- TU Dortmund University, Department of Chemistry and Chemical Biology, Otto-Hahn-Str. 6, 44227, Dortmund, Germany
| | - Lena Nielinger
- TU Dortmund University, Department of Chemistry and Chemical Biology, Otto-Hahn-Str. 6, 44227, Dortmund, Germany
| | - Katharina Alker
- TU Dortmund University, Department of Chemistry and Chemical Biology, Otto-Hahn-Str. 6, 44227, Dortmund, Germany
| | - Jan-Simon Behnke
- TU Dortmund University, Department of Chemistry and Chemical Biology, Otto-Hahn-Str. 6, 44227, Dortmund, Germany
| | - Virginia Wycisk
- TU Dortmund University, Department of Chemistry and Chemical Biology, Otto-Hahn-Str. 6, 44227, Dortmund, Germany
| | - Leonhard H Urner
- TU Dortmund University, Department of Chemistry and Chemical Biology, Otto-Hahn-Str. 6, 44227, Dortmund, Germany
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2
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Duffey M, Jumde RP, da Costa RM, Ropponen HK, Blasco B, Piddock LJ. Extending the Potency and Lifespan of Antibiotics: Inhibitors of Gram-Negative Bacterial Efflux Pumps. ACS Infect Dis 2024; 10:1458-1482. [PMID: 38661541 PMCID: PMC11091901 DOI: 10.1021/acsinfecdis.4c00091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 03/14/2024] [Accepted: 03/20/2024] [Indexed: 04/26/2024]
Abstract
Efflux is a natural process found in all prokaryotic and eukaryotic cells that removes a diverse range of substrates from inside to outside. Many antibiotics are substrates of bacterial efflux pumps, and modifications to the structure or overexpression of efflux pumps are an important resistance mechanism utilized by many multidrug-resistant bacteria. Therefore, chemical inhibition of bacterial efflux to revitalize existing antibiotics has been considered a promising approach for antimicrobial chemotherapy over two decades, and various strategies have been employed. In this review, we provide an overview of bacterial multidrug resistance (MDR) efflux pumps, of which the resistance nodulation division (RND) efflux pumps are considered the most clinically relevant in Gram-negative bacteria, and describe over 50 efflux inhibitors that target such systems. Although numerous efflux inhibitors have been identified to date, none have progressed into clinical use because of formulation, toxicity, and pharmacokinetic issues or a narrow spectrum of inhibition. For these reasons, the development of efflux inhibitors has been considered a difficult and complex area of research, and few active preclinical studies on efflux inhibitors are in progress. However, recently developed tools, including but not limited to computational tools including molecular docking models, offer hope that further research on efflux inhibitors can be a platform for research and development of new bacterial efflux inhibitors.
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Affiliation(s)
- Maëlle Duffey
- Global
Antibiotic Research & Development Partnership (GARDP), Chemin Camille-Vidart 15, 1202 Geneva, Switzerland
| | - Ravindra P. Jumde
- Global
Antibiotic Research & Development Partnership (GARDP), Chemin Camille-Vidart 15, 1202 Geneva, Switzerland
| | - Renata M.A. da Costa
- Global
Antibiotic Research & Development Partnership (GARDP), Chemin Camille-Vidart 15, 1202 Geneva, Switzerland
| | - Henni-Karoliina Ropponen
- Global
Antibiotic Research & Development Partnership (GARDP), Chemin Camille-Vidart 15, 1202 Geneva, Switzerland
| | - Benjamin Blasco
- Global
Antibiotic Research & Development Partnership (GARDP), Chemin Camille-Vidart 15, 1202 Geneva, Switzerland
| | - Laura J.V. Piddock
- Global
Antibiotic Research & Development Partnership (GARDP), Chemin Camille-Vidart 15, 1202 Geneva, Switzerland
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3
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Ricci V, Kaur J, Stone J, Piddock LJV. Antibiotics do not induce expression of acrAB directly but via a RamA-dependent pathway. Antimicrob Agents Chemother 2023; 67:e0062023. [PMID: 37815378 PMCID: PMC10649046 DOI: 10.1128/aac.00620-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 08/09/2023] [Indexed: 10/11/2023] Open
Abstract
The aim of this study was to determine if acrAB induction in Salmonella Typhimurium relies solely on RamA or if other transcriptional activator pathways are also involved, and to better understand the kinetics of induction of both acrAB and ramA. We evaluated the expression of acrAB in S. Typhimurium in response to a variety of compounds that are known to induce the expression of one or more of the transcriptional activators, MarA, SoxS, RamA, and Rob. We utilized green fluorescent protein (GFP) transcriptional reporter fusions to investigate the changes in the expression of acrAB, ramA, marA, and soxS following exposure to sub-inhibitory concentrations of antimicrobial compounds. Of the compounds tested, 13 induce acrAB expression in S. Typhimurium via RamA, MarA, SoxS, and Rob-dependent pathways. None of the tested antibiotics induced acrAB expression, and compounds that induced acrAB expression also induced a general stress response. The results from this study show that the majority of compounds tested induced acrAB via the RamA-dependent pathway. However, none of the antibiotic substrates of the AcrB efflux pump directly increased the expression of AcrAB either directly or indirectly via the induction of one of the transcriptional activators. Using a dual GFP/RFP reporter, we investigated the kinetics of the induction of ramA and acrAB simultaneously and found that acrAB gene expression was transient compared to ramA gene expression. ramA gene expression increased with time and would remain high or decrease slowly over the course of the experiment indicating that RamA exerts a wider global effect and is not limited to efflux regulation alone.
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Affiliation(s)
- Vito Ricci
- Antimicrobials Research Group, Institute of Microbiology and Infection, College of Medical and Dental Science, University of Birmingham, Birmingham, United Kingdom
| | - Jaswant Kaur
- Antimicrobials Research Group, Institute of Microbiology and Infection, College of Medical and Dental Science, University of Birmingham, Birmingham, United Kingdom
| | - Jack Stone
- Antimicrobials Research Group, Institute of Microbiology and Infection, College of Medical and Dental Science, University of Birmingham, Birmingham, United Kingdom
| | - Laura J. V. Piddock
- Antimicrobials Research Group, Institute of Microbiology and Infection, College of Medical and Dental Science, University of Birmingham, Birmingham, United Kingdom
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Maldonado J, Czarnecka B, Harmon DE, Ruiz C. The multidrug efflux pump regulator AcrR directly represses motility in Escherichia coli. mSphere 2023; 8:e0043023. [PMID: 37787551 PMCID: PMC10597343 DOI: 10.1128/msphere.00430-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Accepted: 08/18/2023] [Indexed: 10/04/2023] Open
Abstract
Efflux and motility are two key biological functions in bacteria. Recent findings have shown that efflux impacts flagellum biosynthesis and motility in Escherichia coli and other bacteria. AcrR is known to be the major transcriptional repressor of AcrAB-TolC, the main multidrug efflux pump in E. coli and other Enterobacteriaceae. However, the underlying molecular mechanisms of how efflux and motility are co-regulated remain poorly understood. Here, we have studied the role of AcrR in direct regulation of motility in E. coli. By combining bioinformatics, electrophoretic mobility shift assays (EMSAs), gene expression, and motility experiments, we have found that AcrR represses motility in E. coli by directly repressing transcription of the flhDC operon, but not the other flagellum genes/operons tested. flhDC encodes the master regulator of flagellum biosynthesis and motility genes. We found that such regulation primarily occurs by direct binding of AcrR to the flhDC promoter region containing the first of the two predicted AcrR-binding sites identified in this promoter. This is the first report of direct regulation by AcrR of genes unrelated to efflux or detoxification. Moreover, we report that overexpression of AcrR restores to parental levels the increased swimming motility previously observed in E. coli strains without a functional AcrAB-TolC pump, and that such effect by AcrR is prevented by the AcrR ligand and AcrAB-TolC substrate ethidium bromide. Based on these and prior findings, we provide a novel model in which AcrR senses efflux and then co-regulates efflux and motility in E. coli to maintain homeostasis and escape hazards. IMPORTANCE Efflux and motility play a major role in bacterial growth, colonization, and survival. In Escherichia coli, the transcriptional repressor AcrR is known to directly repress efflux and was later found to also repress flagellum biosynthesis and motility by Kim et al. (J Microbiol Biotechnol 26:1824-1828, 2016, doi: 10.4014/jmb.1607.07058). However, it remained unknown whether AcrR represses flagellum biosynthesis and motility directly and through which target genes, or indirectly because of altering the amount of efflux. This study reveals that AcrR represses flagellum biosynthesis and motility by directly repressing the expression of the flhDC master regulator of flagellum biosynthesis and motility genes, but not the other flagellum genes tested. We also show that the antimicrobial, efflux pump substrate, and AcrR ligand ethidium bromide regulates motility via AcrR. Overall, these findings support a novel model of direct co-regulation of efflux and motility mediated by AcrR in response to stress in E. coli.
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Affiliation(s)
- Jessica Maldonado
- Department of Biology, California State University Northridge, Northridge, California, USA
| | - Barbara Czarnecka
- Department of Biology, California State University Northridge, Northridge, California, USA
| | - Dana E. Harmon
- Department of Biology, California State University Northridge, Northridge, California, USA
| | - Cristian Ruiz
- Department of Biology, California State University Northridge, Northridge, California, USA
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Yamasaki S, Zwama M, Yoneda T, Hayashi-Nishino M, Nishino K. Drug resistance and physiological roles of RND multidrug efflux pumps in Salmonella enterica, Escherichia coli and Pseudomonas aeruginosa. MICROBIOLOGY (READING, ENGLAND) 2023; 169:001322. [PMID: 37319001 PMCID: PMC10333786 DOI: 10.1099/mic.0.001322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Accepted: 03/18/2023] [Indexed: 06/17/2023]
Abstract
Drug efflux pumps transport antimicrobial agents out of bacteria, thereby reducing the intracellular antimicrobial concentration, which is associated with intrinsic and acquired bacterial resistance to these antimicrobials. As genome analysis has advanced, many drug efflux pump genes have been detected in the genomes of bacterial species. In addition to drug resistance, these pumps are involved in various essential physiological functions, such as bacterial adaptation to hostile environments, toxin and metabolite efflux, biofilm formation and quorum sensing. In Gram-negative bacteria, efflux pumps in the resistance–nodulation–division (RND) superfamily play a clinically important role. In this review, we focus on Gram-negative bacteria, including Salmonella enterica , Escherichia coli and Pseudomonas aeruginosa , and discuss the role of RND efflux pumps in drug resistance and physiological functions.
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Affiliation(s)
- Seiji Yamasaki
- SANKEN (The Institute of Scientific and Industrial Research), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
- Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan
- Institute for Advanced Co-Creation Studies, Osaka University, 1-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Martijn Zwama
- SANKEN (The Institute of Scientific and Industrial Research), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
| | - Tomohiro Yoneda
- SANKEN (The Institute of Scientific and Industrial Research), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
- Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Mitsuko Hayashi-Nishino
- SANKEN (The Institute of Scientific and Industrial Research), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
- Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Kunihiko Nishino
- SANKEN (The Institute of Scientific and Industrial Research), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
- Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan
- Center for Infectious Disease Education and Research, 2-8 Yamadaoka, Osaka University, Suita, Osaka 565-0871, Japan
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Guo Y, Gao J, Wang Z, Cui Y, Li Z, Wu Z, Zhao Y, Li D, Dai H. The fate and behavior mechanism of antibiotic resistance genes and microbial communities in flocs, aerobic granular and biofilm sludge under chloroxylenol pressure. JOURNAL OF HAZARDOUS MATERIALS 2022; 438:129465. [PMID: 35785744 DOI: 10.1016/j.jhazmat.2022.129465] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 06/21/2022] [Accepted: 06/24/2022] [Indexed: 06/15/2023]
Abstract
Chloroxylenol (PCMX), an antibacterial agent, has been widely detected in water environment and has toxic effects on biology and ecology. During 270 d, the influence of PCMX on the performance of three nitrification systems was investigated, including floc-based sequencing batch reactor (FSBR), aerobic granule-based SBR (AGSBR) and biofilm SBR (BSBR). The nitrification capability of three systems was inhibited by PCMX, but recovered after domestication, and PCMX made three systems realize partial nitrification for 10, 100 and 35 days, respectively. The extracellular polymeric substances of three systems increased first and then decreased with the increment of PCMX. The granular structure of AGSBR may be conducive to the enrichment of antibiotic resistance genes (ARGs), and almost all ARGs of BSBR were reduced during the addition of 5.0 mg/L PCMX. The microbial community results showed that Rhodococcus as potential degrading bacteria was continuously enriched in three systems. Piscinibacter was regarded as the potential antibiotic resistant bacteria, which was positively associated with multiple ARGs in three systems. Additionally, quaternary ammonium compounds resistance genes had a variety of positive correlations with bacteria in three systems. This study provided a new perspective for the usage and treatment of PCMX.
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Affiliation(s)
- Yi Guo
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Faculty of Environment and Life, Beijing University of Technology, Beijing 100124, China
| | - Jingfeng Gao
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Faculty of Environment and Life, Beijing University of Technology, Beijing 100124, China.
| | - Zhiqi Wang
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Faculty of Environment and Life, Beijing University of Technology, Beijing 100124, China
| | - Yingchao Cui
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Faculty of Environment and Life, Beijing University of Technology, Beijing 100124, China
| | - Ziqiao Li
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Faculty of Environment and Life, Beijing University of Technology, Beijing 100124, China
| | - Zejie Wu
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Faculty of Environment and Life, Beijing University of Technology, Beijing 100124, China
| | - Yifan Zhao
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Faculty of Environment and Life, Beijing University of Technology, Beijing 100124, China
| | - Dingchang Li
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Faculty of Environment and Life, Beijing University of Technology, Beijing 100124, China
| | - Huihui Dai
- National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Faculty of Environment and Life, Beijing University of Technology, Beijing 100124, China
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7
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Wand ME, Darby EM, Blair JMA, Sutton JM. Contribution of the efflux pump AcrAB-TolC to the tolerance of chlorhexidine and other biocides in Klebsiella spp. J Med Microbiol 2022; 71. [PMID: 35324422 PMCID: PMC9176267 DOI: 10.1099/jmm.0.001496] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Introduction. We are becoming increasingly reliant on the effectiveness of biocides to combat the spread of Gram-negative multi-drug-resistant (MDR) pathogens, including Klebsiella pneumoniae. It has been shown that chlorhexidine exposure can lead to mutations in the efflux pump repressor regulators SmvR and RamR, but the contribution of each individual efflux pump to biocide tolerance is unknown. Hypothesis. Multiple efflux pumps, including SmvA and AcrAB-TolC, are involved in increased tolerance to biocides. However, strains with upregulated AcrAB-TolC caused by biocide exposure are more problematic due to their increased MDR phenotype. Aim. To investigate the role of AcrAB-TolC in the tolerance to several biocides, including chlorhexidine, and the potential threat of cross-resistance to antibiotics through increased expression of this efflux pump. Methodology. Antimicrobial susceptibility testing was performed on K. pneumoniae isolates with ramR mutations selected for after exposure to chlorhexidine, as well as transposon mutants in components and regulators of AcrAB-TolC. RTPCR was used to detect the expression levels of this pump after biocide exposure. Strains from the globally important ST258 clade were compared for genetic differences in acrAB-TolC and its regulators and for phenotypic differences in antimicrobial susceptibility. Results. Cross-resistance to antimicrobials was observed following mutations in ramR. Exposure to chlorhexidine led to increased expression of acrA and its activator ramA, and transposon mutants in AcrAB-TolC have increased susceptibility to several biocides, including chlorhexidine. Variations in ramR within the ST258 clade led to an increase in tolerance to certain biocides, although this was strain dependent. One strain, MKP103, that had increased levels of biocide tolerance showed a unique mutation in ramR that was reflected in enhanced expression of acrA and ramA. MKP103 transposon variants were able to further enhance their tolerance to specific biocides with mutations affecting SmvA. Conclusions. Biocide tolerance in K. pneumoniae is dependent upon several components, with increased efflux through AcrAB-TolC being an important one.
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Affiliation(s)
- Matthew E Wand
- UK Health Security Agency, Research and Development, Porton Down, Salisbury, Wiltshire, SP4 0JG, UK
| | - Elizabeth M Darby
- Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Jessica M A Blair
- Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - J Mark Sutton
- UK Health Security Agency, Research and Development, Porton Down, Salisbury, Wiltshire, SP4 0JG, UK
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Kerr R, Jabbari S, Blair JMA, Johnston IG. Dynamic Boolean modelling reveals the influence of energy supply on bacterial efflux pump expression. J R Soc Interface 2022; 19:20210771. [PMID: 35078338 PMCID: PMC8790346 DOI: 10.1098/rsif.2021.0771] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Antimicrobial resistance (AMR) is a global health issue. One key factor contributing to AMR is the ability of bacteria to export drugs through efflux pumps, which relies on the ATP-dependent expression and interaction of several controlling genes. Recent studies have shown that significant cell-to-cell ATP variability exists within clonal bacterial populations, but the contribution of intrinsic cell-to-cell ATP heterogeneity is generally overlooked in understanding efflux pumps. Here, we consider how ATP variability influences gene regulatory networks controlling expression of efflux pump genes in two bacterial species. We develop and apply a generalizable Boolean modelling framework, developed to incorporate the dependence of gene expression dynamics on available cellular energy supply. Theoretical results show that differences in energy availability can cause pronounced downstream heterogeneity in efflux gene expression. Cells with higher energy availability have a superior response to stressors. Furthermore, in the absence of stress, model bacteria develop heterogeneous pulses of efflux pump gene expression which contribute to a sustained sub-population of cells with increased efflux expression activity, potentially conferring a continuous pool of intrinsically resistant bacteria. This modelling approach thus reveals an important source of heterogeneity in cell responses to antimicrobials and sheds light on potentially targetable aspects of efflux pump-related antimicrobial resistance.
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Affiliation(s)
- Ryan Kerr
- School of Mathematics, University of Birmingham, Birmingham, UK.,Institute of Microbiology and Infection, University of Birmingham, Birmingham, UK
| | - Sara Jabbari
- School of Mathematics, University of Birmingham, Birmingham, UK.,Institute of Microbiology and Infection, University of Birmingham, Birmingham, UK
| | - Jessica M A Blair
- Institute of Microbiology and Infection, University of Birmingham, Birmingham, UK
| | - Iain G Johnston
- Department of Mathematics, Faculty of Mathematics and Natural Sciences, University of Bergen, Bergen, Norway.,Computational Biology Unit, University of Bergen, Bergen, Norway.,CAMRIA Centre for Antimicrobial Resistance, Vestland, Norway
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Salcedo-Sora JE, Jindal S, O'Hagan S, Kell DB. A palette of fluorophores that are differentially accumulated by wild-type and mutant strains of Escherichia coli: surrogate ligands for profiling bacterial membrane transporters. MICROBIOLOGY (READING, ENGLAND) 2021; 167:001016. [PMID: 33406033 PMCID: PMC8131027 DOI: 10.1099/mic.0.001016] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 12/15/2020] [Indexed: 12/12/2022]
Abstract
Our previous work demonstrated that two commonly used fluorescent dyes that were accumulated by wild-type Escherichia coli MG1655 were differentially transported in single-gene knockout strains, and also that they might be used as surrogates in flow cytometric transporter assays. We summarize the desirable properties of such stains, and here survey 143 candidate dyes. We eventually triage them (on the basis of signal, accumulation levels and cost) to a palette of 39 commercially available and affordable fluorophores that are accumulated significantly by wild-type cells of the 'Keio' strain BW25113, as measured flow cytometrically. Cheminformatic analyses indicate both their similarities and their (much more considerable) structural differences. We describe the effects of pH and of the efflux pump inhibitor chlorpromazine on the accumulation of the dyes. Even the 'wild-type' MG1655 and BW25113 strains can differ significantly in their ability to take up such dyes. We illustrate the highly differential uptake of our dyes into strains with particular lesions in, or overexpressed levels of, three particular transporters or transporter components (yhjV, yihN and tolC). The relatively small collection of dyes described offers a rapid, inexpensive, convenient and informative approach to the assessment of microbial physiology and phenotyping of membrane transporter function.
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Affiliation(s)
- Jesus Enrique Salcedo-Sora
- Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Crown St, Liverpool L69 7ZB, UK
| | - Srijan Jindal
- Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Crown St, Liverpool L69 7ZB, UK
| | - Steve O'Hagan
- Department of Chemistry and Manchester Institute of Biotechnology, The University of Manchester, 131 Princess St, Manchester M1 7DN, UK
| | - Douglas B. Kell
- Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Crown St, Liverpool L69 7ZB, UK
- Novo Nordisk Foundation Centre for Biosustainability, Technical University of Denmark, Building 220, Kemitorvet, 2800 Kgs Lyngby, Denmark
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10
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Piddock LJV. The 2019 Garrod Lecture: MDR efflux in Gram-negative bacteria-how understanding resistance led to a new tool for drug discovery. J Antimicrob Chemother 2020; 74:3128-3134. [PMID: 31626705 DOI: 10.1093/jac/dkz370] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The AcrAB-TolC MDR efflux system confers intrinsic MDR and overproduction confers clinically relevant resistance to some antibiotics active against Gram-negative bacteria. The system is made up of three components, namely AcrA, AcrB and TolC, otherwise known as the AcrAB-TolC tripartite system. Inactivation or deletion of a gene encoding one of the constituent proteins, or substitution of a single amino acid in the efflux pump component AcrB that results in loss of efflux function, confers increased antibiotic susceptibility. Clinically relevant resistance can be mediated by a mutation in acrB that changes the way AcrB substrates are transported. However, it is more common that resistant clinical and veterinary isolates overproduce the AcrAB-TolC MDR efflux system. This is due to mutations in genes such as marR and ramR that encode repressors of transcription factors (MarA and RamA, respectively) that when produced activate expression of the acrAB and tolC genes thereby increasing efflux. The Lon protease degrades MarA and RamA to return the level of efflux to that of the WT. Furthermore, the levels of AcrAB-TolC are regulated by CsrA. Studies with fluorescent reporters that report levels of acrAB and regulatory factors allowed the development of a new tool for discovering efflux inhibitors. Screens of the Prestwick Chemical Library and a large library from a collaborating pharmaceutical company have generated a number of candidate compounds for further research.
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Affiliation(s)
- Laura J V Piddock
- Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, UK
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11
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Abstract
Active efflux of antibiotics preventing their accumulation to toxic intracellular concentrations contributes to clinically relevant multidrug resistance. Inhibition of active efflux potentiates antibiotic activity, indicating that efflux inhibitors could be used in combination with antibiotics to reverse drug resistance. Expression of ramA by Salmonella enterica serovar Typhimurium increases in response to efflux inhibition, irrespective of the mode of inhibition. We hypothesized that measuring ramA promoter activity could act as a reporter of efflux inhibition. A rapid, inexpensive, and high-throughput green fluorescent protein (GFP) screen to identify efflux inhibitors was developed, validated, and implemented. Two chemical compound libraries were screened for compounds that increased GFP production. Fifty of the compounds in the 1,200-compound Prestwick chemical library were identified as potential efflux inhibitors, including the previously characterized efflux inhibitors mefloquine and thioridazine. There were 107 hits from a library of 47,168 proprietary compounds from L. Hoffmann La Roche; 45 were confirmed hits, and a dose response was determined. Dye efflux and accumulation assays showed that 40 Roche and three Prestwick chemical library compounds were efflux inhibitors. Most compounds had specific efflux-inhibitor-antibiotic combinations and/or species-specific synergy in antibiotic disc diffusion and checkerboard assays performed with Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, and Salmonella Typhimurium. These data indicate that both narrow-spectrum and broad-spectrum combinations of efflux inhibitors with antibiotics can be found. Eleven novel efflux inhibitor compounds potentiated antibiotic activities against at least one species of Gram-negative bacteria, and data revealing an E. coli mutant with loss of AcrB function suggested that these are AcrB inhibitors.IMPORTANCE Multidrug-resistant Gram-negative bacteria pose a serious threat to human and animal health. Molecules that inhibit multidrug efflux offer an alternative approach to resolving the challenges caused by antibiotic resistance, by potentiating the activity of old, licensed, and new antibiotics. We have developed, validated, and implemented a high-throughput screen and used it to identify efflux inhibitors from two compound libraries selected for their high chemical and pharmacological diversity. We found that the new high-throughput screen is a valuable tool to identify efflux inhibitors, as evidenced by the 43 new efflux inhibitors described in this study.
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12
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Grimsey EM, Piddock LJV. Do phenothiazines possess antimicrobial and efflux inhibitory properties? FEMS Microbiol Rev 2020; 43:577-590. [PMID: 31216574 DOI: 10.1093/femsre/fuz017] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 06/12/2019] [Indexed: 12/30/2022] Open
Abstract
Antibiotic resistance is a global health concern; the rise of drug-resistant bacterial infections is compromising the medical advances that resulted from the introduction of antibiotics at the beginning of the 20th century. Considering that the presence of mutations within individuals in a bacterial population may allow a subsection to survive and propagate in response to selective pressure, as long as antibiotics are used in the treatment of bacterial infections, development of resistance is an inevitable evolutionary outcome. This, combined with the lack of novel antibiotics being released to the clinical market, means the need to develop alternative strategies to treat these resistant infections is critical. We discuss how the use of antibiotic adjuvants can minimise the appearance and impact of resistance. To this effect, several phenothiazine-derived drugs have been shown to potentiate the activities of antibiotics used to treat infections caused by Gram-positive and Gram-negative bacteria. Outside of their role as antipsychotic medications, we review the evidence to suggest that phenothiazines possess inherent antibacterial and efflux inhibitory properties enabling them to potentially combat drug resistance. We also discuss that understanding their mode of action is essential to facilitate the design of new phenothiazine derivatives or novel agents for use as antibiotic adjuvants.
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Affiliation(s)
- Elizabeth M Grimsey
- Institute of Microbiology & Infection, College of Medical & Dental Sciences, University of Birmingham, Edgbaston, United Kingdom
| | - Laura J V Piddock
- Institute of Microbiology & Infection, College of Medical & Dental Sciences, University of Birmingham, Edgbaston, United Kingdom
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13
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Abstract
Efflux is an important mechanism in Gram-negative bacteria conferring multidrug resistance. Inhibition of efflux is an encouraging strategy to restore the antibacterial activity of antibiotics. Chlorpromazine and amitriptyline have been shown to behave as efflux inhibitors. However, their mode of action is poorly understood. Exposure of Salmonella enterica serovar Typhimurium and Escherichia coli to chlorpromazine selected for mutations within genes encoding RamR and MarR, regulators of the multidrug tripartite efflux pump AcrAB-TolC. Further experiments with S. Typhimurium containing AcrB D408A (a nonfunctional efflux pump) and chlorpromazine or amitriptyline resulted in the reversion of the mutant acrB allele to the wild type. Together, this suggests these drugs are AcrB efflux substrates. Subsequent docking studies with AcrB from S. Typhimurium and E. coli, followed by molecular dynamics simulations and free energy calculations showed that chlorpromazine and amitriptyline bind at the hydrophobic trap, a preferred binding site for substrates and inhibitors within the distal binding pocket of AcrB. Based on these simulations, we suggest that chlorpromazine and amitriptyline inhibit AcrB-mediated efflux by interfering with substrate binding. Our findings provide evidence that these drugs are substrates and inhibitors of AcrB, yielding molecular details of their mechanism of action and informing drug discovery of new efflux inhibitors.IMPORTANCE Efflux pumps of the resistance nodulation-cell division (RND) superfamily are major contributors to multidrug resistance for most of the Gram-negative ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens. The development of inhibitors of these pumps would be highly desirable; however, several issues have thus far hindered all efforts at designing new efflux inhibitory compounds devoid of adverse effects. An alternative route to de novo design relies on the use of marketed drugs, for which side effects on human health have been already assessed. In this work, we provide experimental evidence that the antipsychotic drugs chlorpromazine and amitriptyline are inhibitors of the AcrB transporter, the engine of the major RND efflux pumps in Escherichia coli and Salmonella enterica serovar Typhimurium. Furthermore, in silico calculations have provided a molecular-level picture of the inhibition mechanism, allowing rationalization of experimental data and paving the way for similar studies with other classes of marketed compounds.
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14
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Colclough AL, Alav I, Whittle EE, Pugh HL, Darby EM, Legood SW, McNeil HE, Blair JM. RND efflux pumps in Gram-negative bacteria; regulation, structure and role in antibiotic resistance. Future Microbiol 2020; 15:143-157. [PMID: 32073314 DOI: 10.2217/fmb-2019-0235] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Rresistance-nodulation-division (RND) efflux pumps in Gram-negative bacteria remove multiple, structurally distinct classes of antimicrobials from inside bacterial cells therefore directly contributing to multidrug resistance. There is also emerging evidence that many other mechanisms of antibiotic resistance rely on the intrinsic resistance conferred by RND efflux. In addition to their role in antibiotic resistance, new information has become available about the natural role of RND pumps including their established role in virulence of many Gram-negative organisms. This review also discusses the recent advances in understanding the regulation and structure of RND efflux pumps.
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Affiliation(s)
- Abigail L Colclough
- Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Ilyas Alav
- Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Emily E Whittle
- Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Hannah L Pugh
- Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Elizabeth M Darby
- Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Simon W Legood
- Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Helen E McNeil
- Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Jessica Ma Blair
- Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
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15
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Whittle EE, Legood SW, Alav I, Dulyayangkul P, Overton TW, Blair JMA. Flow Cytometric Analysis of Efflux by Dye Accumulation. Front Microbiol 2019; 10:2319. [PMID: 31636625 PMCID: PMC6787898 DOI: 10.3389/fmicb.2019.02319] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 09/23/2019] [Indexed: 11/13/2022] Open
Abstract
Gram-negative infections are increasingly difficult to treat because of their impermeable outer membranes (OM) and efflux pumps which maintain a low intracellular accumulation of antibiotics within cells. Historically, measurement of accumulation of drugs or dyes within Gram-negative cells has concentrated on analyzing whole bacterial populations. Here, we have developed a method to measure the intracellular accumulation of ethidium bromide, a fluorescent DNA intercalating dye, in single cells using flow cytometry. Bacterial cells were stained with SYTOTM 84 to easily separate cells from background cell debris. Ethidium bromide fluorescence was then measured within the SYTOTM 84 positive population to measure accumulation. In S. Typhimurium SL1344, ethidium bromide accumulation was low, however, in a number of efflux mutants, accumulation of ethidium bromide increased more than twofold, comparable to previous whole population analysis of accumulation. We demonstrate simultaneous measurement of ethidium bromide accumulation and GFP allowing quantification of gene expression or other facets of phenotype in single cells. In addition, we show here that this assay can be adapted for use with efflux inhibitors, with both Gram-negative and Gram-positive bacteria, and with other fluorescent substrates with different fluorescence spectra.
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Affiliation(s)
- Emily E Whittle
- College of Medical and Dental Sciences, Institute of Microbiology and Infection, University of Birmingham, Birmingham, United Kingdom
| | - Simon W Legood
- College of Medical and Dental Sciences, Institute of Microbiology and Infection, University of Birmingham, Birmingham, United Kingdom
| | - Ilyas Alav
- College of Medical and Dental Sciences, Institute of Microbiology and Infection, University of Birmingham, Birmingham, United Kingdom
| | - Punyawee Dulyayangkul
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, United Kingdom
| | - Tim W Overton
- School of Chemical Engineering, University of Birmingham, Birmingham, United Kingdom
| | - Jessica M A Blair
- College of Medical and Dental Sciences, Institute of Microbiology and Infection, University of Birmingham, Birmingham, United Kingdom
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16
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Jindal S, Yang L, Day PJ, Kell DB. Involvement of multiple influx and efflux transporters in the accumulation of cationic fluorescent dyes by Escherichia coli. BMC Microbiol 2019; 19:195. [PMID: 31438868 PMCID: PMC6704527 DOI: 10.1186/s12866-019-1561-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 07/31/2019] [Indexed: 12/11/2022] Open
Abstract
Background It is widely believed that most xenobiotics cross biomembranes by diffusing through the phospholipid bilayer, and that the use of protein transporters is an occasional adjunct. According to an alternative view, phospholipid bilayer transport is negligible, and several different transporters may be involved in the uptake of an individual molecular type. We recognise here that the availability of gene knockout collections allows one to assess the contributions of all potential transporters, and flow cytometry based on fluorescence provides a convenient high-throughput assay for xenobiotic uptake in individual cells. Results We used high-throughput flow cytometry to assess the ability of individual gene knockout strains of E coli to take up two membrane-permeable, cationic fluorescent dyes, namely the carbocyanine diS-C3(5) and the DNA dye SYBR Green. Individual strains showed a large range of distributions of uptake. The range of modal steady-state uptakes for the carbocyanine between the different strains was 36-fold. Knockouts of the ATP synthase α- and β-subunits greatly inhibited uptake, implying that most uptake was ATP-driven rather than being driven by a membrane potential. Dozens of transporters changed the steady-state uptake of the dye by more than 50% with respect to that of the wild type, in either direction (increased or decreased); knockouts of known influx and efflux transporters behaved as expected, giving credence to the general strategy. Many of the knockouts with the most reduced uptake were transporter genes of unknown function (‘y-genes’). Similarly, several overexpression variants in the ‘ASKA’ collection had the anticipated, opposite effects. Similar results were obtained with SYBR Green (the range being approximately 69-fold). Although it too contains a benzothiazole motif there was negligible correlation between its uptake and that of the carbocyanine when compared across the various strains (although the membrane potential is presumably the same in each case). Conclusions Overall, we conclude that the uptake of these dyes may be catalysed by a great many transporters of putatively broad and presently unknown specificity, and that the very large range between the ‘lowest’ and the ‘highest’ levels of uptake, even in knockouts of just single genes, implies strongly that phospholipid bilayer transport is indeed negligible. This work also casts serious doubt upon the use of such dyes as quantitative stains for representing either bioenergetic parameters or the amount of cellular DNA in unfixed cells (in vivo). By contrast, it opens up their potential use as transporter assay substrates in high-throughput screening. Electronic supplementary material The online version of this article (10.1186/s12866-019-1561-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Srijan Jindal
- Department of Chemistry, The University of Manchester, 131 Princess St, Manchester, M1 7DN, UK.,Manchester Institute of Biotechnology, The University of Manchester, 131 Princess St, Manchester, M1 7DN, UK.,Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, UK
| | - Lei Yang
- Novo Nordisk Foundation Centre for Biosustainability, Technical University of Denmark, Building 220, Kemitorvet, 2800 Kgs, Lyngby, Denmark
| | - Philip J Day
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess St, Manchester, M1 7DN, UK.,Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, UK
| | - Douglas B Kell
- Department of Chemistry, The University of Manchester, 131 Princess St, Manchester, M1 7DN, UK. .,Manchester Institute of Biotechnology, The University of Manchester, 131 Princess St, Manchester, M1 7DN, UK. .,Novo Nordisk Foundation Centre for Biosustainability, Technical University of Denmark, Building 220, Kemitorvet, 2800 Kgs, Lyngby, Denmark. .,Department of Biochemistry, Institute of Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Crown St, Liverpool, L69 7ZB, UK.
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17
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Anes J, Sivasankaran SK, Muthappa DM, Fanning S, Srikumar S. Exposure to Sub-inhibitory Concentrations of the Chemosensitizer 1-(1-Naphthylmethyl)-Piperazine Creates Membrane Destabilization in Multi-Drug Resistant Klebsiella pneumoniae. Front Microbiol 2019; 10:92. [PMID: 30814979 PMCID: PMC6381021 DOI: 10.3389/fmicb.2019.00092] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 01/16/2019] [Indexed: 01/23/2023] Open
Abstract
Antimicrobial efflux is one of the important mechanisms causing multi-drug resistance (MDR) in bacteria. Chemosensitizers like 1-(1-naphthylmethyl)-piperazine (NMP) can inhibit an efflux pump and therefore can overcome MDR. However, secondary effects of NMP other than efflux pump inhibition are rarely investigated. Here, using phenotypic assays, phenotypic microarray and transcriptomic assays we show that NMP creates membrane destabilization in MDR Klebsiella pneumoniae MGH 78578 strain. The NMP mediated membrane destabilization activity was measured using β-lactamase activity, membrane potential alteration studies, and transmission electron microscopy assays. Results from both β-lactamase and membrane potential alteration studies shows that both outer and inner membranes are destabilized in NMP exposed K. pneumoniae MGH 78578 cells. Phenotypic Microarray and RNA-seq were further used to elucidate the metabolic and transcriptional signals underpinning membrane destabilization. Membrane destabilization happens as early as 15 min post-NMP treatment. Our RNA-seq data shows that many genes involved in envelope stress response were differentially regulated in the NMP treated cells. Up-regulation of genes encoding the envelope stress response and repair systems show the distortion in membrane homeostasis during survival in an environment containing sub-inhibitory concentration of NMP. In addition, the lsr operon encoding the production of autoinducer-2 responsible for biofilm production was down-regulated resulting in reduced biofilm formation in NMP treated cells, a phenotype confirmed by crystal violet-based assays. We postulate that the early membrane disruption leads to destabilization of inner membrane potential, impairing ATP production and consequently resulting in efflux pump inhibition.
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Affiliation(s)
- João Anes
- School of Public Health, Physiotherapy and Sports Science, Centre for Food Safety, Science Centre South, University College Dublin, Dublin, Ireland
| | | | - Dechamma M Muthappa
- School of Public Health, Physiotherapy and Sports Science, Centre for Food Safety, Science Centre South, University College Dublin, Dublin, Ireland
| | - Séamus Fanning
- School of Public Health, Physiotherapy and Sports Science, Centre for Food Safety, Science Centre South, University College Dublin, Dublin, Ireland.,Institute for Global Food Security, Queen's University Belfast, Belfast, United Kingdom
| | - Shabarinath Srikumar
- School of Public Health, Physiotherapy and Sports Science, Centre for Food Safety, Science Centre South, University College Dublin, Dublin, Ireland
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18
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Anes J, Martins M, Fanning S. Reversing Antimicrobial Resistance in Multidrug-Resistant Klebsiella pneumoniae of Clinical Origin Using 1-(1-Naphthylmethyl)-Piperazine. Microb Drug Resist 2018; 24:1497-1506. [PMID: 30004292 DOI: 10.1089/mdr.2017.0386] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Eleven clinical Klebsiella pneumoniae fluoroquinolone-resistant isolates were tested to access the potential of adjuvant therapies to reduce antimicrobial resistance using fixed concentrations of the chemosensitizers chlorpromazine (CPZ), thioridazine (TZ), phenylalanine-arginine-β-naphthylamide (PAβN), and 1-(1-naphthylmethyl)-piperazine-(NMP) with varying concentrations of antimicrobial agents nalidixic acid (NAL), ciprofloxacin (CIP), moxifloxacin (MXF), tetracycline (TET), and chloramphenicol (CHL). Ethidium bromide dye was used together with the chemosensitizers to investigate permeabilization effects. NMP was assessed for its capacity to reduce the mass of biofilm alone and in combination with CIP and MXF. Of the selected chemosensitizers, NMP exhibited the greatest capacity to reverse resistance and inhibit efflux, based on the concentrations tested. Susceptibility to antimicrobial agents including (fluoro)quinolones, TET, and CHL were found to be increased in the presence of NMP, in a concentration-dependent manner. PAβN also demonstrated similar effects when combined with the chemosensitizers tested. In the case of half of the isolates studied, NMP alone reduced preformed biofilm biomass. Combinations of latter along with CIP or MXF were also found to reduce the mass of preformed biofilm, in the case of only some of the bacterial isolates. The capacity of NMP to reduce antimicrobial resistance could be of relevance as a strategy to limit bacterial colonization on abiotic surfaces.
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Affiliation(s)
- João Anes
- 1 School of Public Health, Physiotherapy and Sports Science, UCD Centre for Food Safety, University College Dublin , Dublin, Ireland
| | - Marta Martins
- 1 School of Public Health, Physiotherapy and Sports Science, UCD Centre for Food Safety, University College Dublin , Dublin, Ireland
| | - Séamus Fanning
- 1 School of Public Health, Physiotherapy and Sports Science, UCD Centre for Food Safety, University College Dublin , Dublin, Ireland
- 2 Institute for Global Food Security, Queen's University Belfast , Belfast, United Kingdom
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19
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Ricci V, Attah V, Overton T, Grainger DC, Piddock LJV. CsrA maximizes expression of the AcrAB multidrug resistance transporter. Nucleic Acids Res 2018; 45:12798-12807. [PMID: 29040729 PMCID: PMC5727465 DOI: 10.1093/nar/gkx929] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 10/02/2017] [Indexed: 01/30/2023] Open
Abstract
Carbon Storage Regulator A (CsrA) is an RNA binding protein that acts as a global regulator of diverse genes. Using a combination of genetics and biochemistry we show that CsrA binds directly to the 5′ end of the transcript encoding AcrAB. Deletion of csrA or mutagenesis of the CsrA binding sites reduced production of both AcrA and AcrB. Nucleotide substitutions at the 5′ UTR of acrA mRNA that could potentially weaken the inhibitory RNA secondary structure, allow for more efficient translation of the AcrAB proteins. Given the role of AcrAB-TolC in multi-drug efflux we suggest that CsrA is a potential drug target.
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Affiliation(s)
- Vito Ricci
- Antimicrobials Research Group, School of Immunity and Infection, College of Medical and Dental Sciences, Institute of Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, UK
| | - Victoria Attah
- Antimicrobials Research Group, School of Immunity and Infection, College of Medical and Dental Sciences, Institute of Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, UK
| | - Tim Overton
- Bioengineering, School of Chemical Engineering, University of Birmingham, Birmingham B15 2TT, UK
| | - David C Grainger
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Laura J V Piddock
- Antimicrobials Research Group, School of Immunity and Infection, College of Medical and Dental Sciences, Institute of Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, UK
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20
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Molitor A, James CE, Fanning S, Pagès JM, Davin-Regli A. Ram locus is a key regulator to trigger multidrug resistance in Enterobacter aerogenes. J Med Microbiol 2018; 67:148-159. [PMID: 29297851 DOI: 10.1099/jmm.0.000667] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
PURPOSE Several genetic regulators belonging to AraC family are involved in the emergence of MDR isolates of E. aerogenes due to alterations in membrane permeability. Compared with the genetic regulator Mar, RamA may be more relevant towards the emergence of antibiotic resistance. METHODOLOGY Focusing on the global regulators, Mar and Ram, we compared the amino acid sequences of the Ram repressor in 59 clinical isolates and laboratory strains of E. aerogenes. Sequence types were associated with their corresponding multi-drug resistance phenotypes and membrane protein expression profiles using MIC and immunoblot assays. Quantitative gene expression analysis of the different regulators and their targets (porins and efflux pump components) were performed. RESULTS In the majority of the MDR isolates tested, ramR and a region upstream of ramA were mutated but marR or marA were unchanged. Expression and cloning experiments highlighted the involvement of the ram locus in the modification of membrane permeability. Overexpression of RamA lead to decreased porin production and increased expression of efflux pump components, whereas overexpression of RamR had the opposite effects. CONCLUSION Mutations or deletions in ramR, leading to the overexpression of RamA predominated in clinical MDR E. aerogenes isolates and were associated with a higher-level of expression of efflux pump components. It was hypothesised that mutations in ramR, and the self-regulating region proximal to ramA, probably altered the binding properties of the RamR repressor; thereby producing the MDR phenotype. Consequently, mutability of RamR may play a key role in predisposing E. aerogenes towards the emergence of a MDR phenotype.
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Affiliation(s)
- Alexander Molitor
- UMR_MD1, Facultés de Pharmacie and Médecine, Aix-Marseille Univ, Marseille, France
| | - Chloë E James
- Biomedical Research Centre and Ecosystems and Environment Research Centre, School of Environment and Life Sciences, University of Salford, Salford, M5 4WT, UK
| | - Séamus Fanning
- School of Public Health, Physiotherapy and Sports Science, UCD-Centre For Food Safety, University College Dublin, Belfield, Dublin D4 N2E5, Ireland
| | - Jean-Marie Pagès
- UMR_MD1, Facultés de Pharmacie and Médecine, Aix-Marseille Univ, Marseille, France
| | - Anne Davin-Regli
- UMR_MD1, Facultés de Pharmacie and Médecine, Aix-Marseille Univ, Marseille, France
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21
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Weston N, Sharma P, Ricci V, Piddock LJV. Regulation of the AcrAB-TolC efflux pump in Enterobacteriaceae. Res Microbiol 2017; 169:425-431. [PMID: 29128373 DOI: 10.1016/j.resmic.2017.10.005] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 10/16/2017] [Accepted: 10/31/2017] [Indexed: 11/18/2022]
Abstract
Bacterial multidrug efflux systems are a major mechanism of antimicrobial resistance and are fundamental to the physiology of Gram-negative bacteria. The resistance-nodulation-division (RND) family of efflux pumps is the most clinically significant, as it is associated with multidrug resistance. Expression of efflux systems is subject to multiple levels of regulation, involving local and global transcriptional regulation as well as post-transcriptional and post-translational regulation. The best-characterised RND system is AcrAB-TolC, which is present in Enterobacteriaceae. This review describes the current knowledge and new data about the regulation of the acrAB and tolC genes in Escherichia coli and Salmonella enterica.
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Affiliation(s)
- Natasha Weston
- Institute of Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Prateek Sharma
- Institute of Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Vito Ricci
- Institute of Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Laura J V Piddock
- Institute of Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, United Kingdom.
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22
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Abstract
AcrAB-TolC is the paradigm resistance-nodulation-division (RND) multidrug resistance efflux system in Gram-negative bacteria, with AcrB being the pump protein in this complex. We constructed a nonfunctional AcrB mutant by replacing D408, a highly conserved residue essential for proton translocation. Western blotting confirmed that the AcrB D408A mutant had the same native level of expression of AcrB as the parental strain. The mutant had no growth deficiencies in rich or minimal medium. However, compared with wild-type SL1344, the mutant had increased accumulation of Hoechst 33342 dye and decreased efflux of ethidium bromide and was multidrug hypersusceptible. The D408A mutant was attenuated in vivo in mouse and Galleria mellonella models and showed significantly reduced invasion into intestinal epithelial cells and macrophages in vitro A dose-dependent inhibition of invasion was also observed when two different efflux pump inhibitors were added to the wild-type strain during infection of epithelial cells. RNA sequencing (RNA-seq) revealed downregulation of bacterial factors necessary for infection, including those in the Salmonella pathogenicity islands 1, 2, and 4; quorum sensing genes; and phoPQ Several general stress response genes were upregulated, probably due to retention of noxious molecules inside the bacterium. Unlike loss of AcrB protein, loss of efflux function did not induce overexpression of other RND efflux pumps. Our data suggest that gene deletion mutants are unsuitable for studying membrane transporters and, importantly, that inhibitors of AcrB efflux function will not induce expression of other RND pumps.IMPORTANCE Antibiotic resistance is a major public health concern. In Gram-negative bacteria, overexpression of the AcrAB-TolC multidrug efflux system confers resistance to clinically useful drugs. Here, we show that loss of AcrB efflux function causes loss of virulence in Salmonella enterica serovar Typhimurium. This is due to the reduction of bacterial factors necessary for infection, which is likely to be caused by the retention of noxious molecules inside the bacterium. We also show that, in contrast to loss of AcrB protein, loss of efflux does not induce overexpression of other efflux pumps from the same family. This indicates that there are differences between loss of efflux protein and loss of efflux that make gene deletion mutants unsuitable for studying the biological function of membrane transporters. Understanding the biological role of AcrB will help to assess the risks of targeting efflux pumps as a strategy to combat antibiotic resistance.
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23
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Xie X, Zhang H, Zheng Y, Li A, Wang M, Zhou H, Zhu X, Schneider Z, Chen L, Kreiswirth BN, Du H. RpoE is a Putative Antibiotic Resistance Regulator of Salmonella enteric Serovar Typhi. Curr Microbiol 2016; 72:457-64. [PMID: 26742769 DOI: 10.1007/s00284-015-0983-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 12/02/2015] [Indexed: 11/27/2022]
Abstract
Bacterial antimicrobial resistance has been associated with the up regulation of genes encoding efflux pumps and the down regulation of genes encoding outer membrane proteins (OMPs). Gene expression in bacteria is primarily initiated by sigma factors (σ factors) such as RpoE, which plays an important role in responding to many environmental stresses. Here, we report the first observation that RpoE serves as an antibiotic resistance regulator in Salmonella enteric serovar Typhi (S. Typhi). In this study, we found that the rpoE mutant (ΔrpoE) of S. Typhi GIFU10007 has elevated resistance to several antimicrobial agents, including β-lactams, quinolones, and aminoglycosides. Genomic DNA microarray analysis was used to investigate the differential gene expression profiles between a wild type and rpoE mutant in response to ampicillin. The results showed that a total of 57 genes displayed differential expression (two-fold increase or decrease) in ΔrpoE versus the wild-type strain. The expressions of two outer membrane protein genes, ompF and ompC, were significantly down-regulated in ΔrpoE (six and seven-fold lower in comparison to wild-type strain) and RamA, a member of the efflux pump AraC/XylS family, was up-regulated about four-fold in the ΔrpoE. Our results suggest RpoE is a potential antimicrobial regulator in S. Typhi, controlling both the down regulation of the OMP genes and up-regulating the efflux system.
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Affiliation(s)
- Xiaofang Xie
- Department of Clinical Laboratory, The Second Affiliated Hospital of Soochow University, Suzhou, 215004, Jiangsu, People's Republic of China
| | - Haifang Zhang
- Department of Clinical Laboratory, The Second Affiliated Hospital of Soochow University, Suzhou, 215004, Jiangsu, People's Republic of China
| | - Yi Zheng
- Department of Clinical Laboratory, The Second Affiliated Hospital of Soochow University, Suzhou, 215004, Jiangsu, People's Republic of China
| | - Aiqing Li
- Department of Clinical Laboratory, The Second Affiliated Hospital of Soochow University, Suzhou, 215004, Jiangsu, People's Republic of China
| | - Min Wang
- Department of Clinical Laboratory, The Second Affiliated Hospital of Soochow University, Suzhou, 215004, Jiangsu, People's Republic of China
| | - Huiqin Zhou
- Department of Clinical Laboratory, The Second Affiliated Hospital of Soochow University, Suzhou, 215004, Jiangsu, People's Republic of China
| | - Xueming Zhu
- Department of Clinical Laboratory, The Second Affiliated Hospital of Soochow University, Suzhou, 215004, Jiangsu, People's Republic of China
| | - Zachary Schneider
- Public Health Research Institute Center, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA
| | - Liang Chen
- Public Health Research Institute Center, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA
| | - Barry N Kreiswirth
- Public Health Research Institute Center, New Jersey Medical School, Rutgers University, Newark, NJ, 07103, USA
| | - Hong Du
- Department of Clinical Laboratory, The Second Affiliated Hospital of Soochow University, Suzhou, 215004, Jiangsu, People's Republic of China.
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Davin-Regli A, Pagès JM. Enterobacter aerogenes and Enterobacter cloacae; versatile bacterial pathogens confronting antibiotic treatment. Front Microbiol 2015; 6:392. [PMID: 26042091 PMCID: PMC4435039 DOI: 10.3389/fmicb.2015.00392] [Citation(s) in RCA: 300] [Impact Index Per Article: 33.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 04/16/2015] [Indexed: 12/14/2022] Open
Abstract
Enterobacter aerogenes and E. cloacae have been reported as important opportunistic and multiresistant bacterial pathogens for humans during the last three decades in hospital wards. These Gram-negative bacteria have been largely described during several outbreaks of hospital-acquired infections in Europe and particularly in France. The dissemination of Enterobacter sp. is associated with the presence of redundant regulatory cascades that efficiently control the membrane permeability ensuring the bacterial protection and the expression of detoxifying enzymes involved in antibiotic degradation/inactivation. In addition, these bacterial species are able to acquire numerous genetic mobile elements that strongly contribute to antibiotic resistance. Moreover, this particular fitness help them to colonize several environments and hosts and rapidly and efficiently adapt their metabolism and physiology to external conditions and environmental stresses. Enterobacter is a versatile bacterium able to promptly respond to the antibiotic treatment in the colonized patient. The balance of the prevalence, E. aerogenes versus E. cloacae, in the reported hospital infections during the last period, questions about the horizontal transmission of mobile elements containing antibiotic resistance genes, e.g., the efficacy of the exchange of resistance genes Klebsiella pneumoniae to Enterobacter sp. It is also important to mention the possible role of antibiotic use in the treatment of bacterial infectious diseases in this E. aerogenes/E. cloacae evolution.
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Affiliation(s)
- Anne Davin-Regli
- Transporteurs Membranaires, Chimiorésistance et Drug Design, Facultés de Médecine et Pharmacie, UMR-MD1, IRBA - Aix-Marseille Université, Marseille France
| | - Jean-Marie Pagès
- Transporteurs Membranaires, Chimiorésistance et Drug Design, Facultés de Médecine et Pharmacie, UMR-MD1, IRBA - Aix-Marseille Université, Marseille France
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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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AcrB drug-binding pocket substitution confers clinically relevant resistance and altered substrate specificity. Proc Natl Acad Sci U S A 2015; 112:3511-6. [PMID: 25737552 DOI: 10.1073/pnas.1419939112] [Citation(s) in RCA: 125] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The incidence of multidrug-resistant bacterial infections is increasing globally and the need to understand the underlying mechanisms is paramount to discover new therapeutics. The efflux pumps of Gram-negative bacteria have a broad substrate range and transport antibiotics out of the bacterium, conferring intrinsic multidrug resistance (MDR). The genomes of pre- and posttherapy MDR clinical isolates of Salmonella Typhimurium from a patient that failed antibacterial therapy and died were sequenced. In the posttherapy isolate we identified a novel G288D substitution in AcrB, the resistance-nodulation division transporter in the AcrAB-TolC tripartite MDR efflux pump system. Computational structural analysis suggested that G288D in AcrB heavily affects the structure, dynamics, and hydration properties of the distal binding pocket altering specificity for antibacterial drugs. Consistent with this hypothesis, recreation of the mutation in standard Escherichia coli and Salmonella strains showed that G288D AcrB altered substrate specificity, conferring decreased susceptibility to the fluoroquinolone antibiotic ciprofloxacin by increased efflux. At the same time, the substitution increased susceptibility to other drugs by decreased efflux. Information about drug transport is vital for the discovery of new antibacterials; the finding that one amino acid change can cause resistance to some drugs, while conferring increased susceptibility to others, could provide a basis for new drug development and treatment strategies.
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Blair JMA, Smith HE, Ricci V, Lawler AJ, Thompson LJ, Piddock LJV. Expression of homologous RND efflux pump genes is dependent upon AcrB expression: implications for efflux and virulence inhibitor design. J Antimicrob Chemother 2014; 70:424-31. [PMID: 25288678 PMCID: PMC4291234 DOI: 10.1093/jac/dku380] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Objectives Enterobacteriaceae have multiple efflux pumps that confer intrinsic resistance to antibiotics. AcrB mediates clinically relevant multidrug resistance and is required for virulence and biofilm formation, making it an attractive target for the design of inhibitors. The aim of this study was to assess the viability of single transporters as a target for efflux inhibition using Salmonella Typhimurium as the model pathogen. Methods The expression of resistance–nodulation–division (RND) efflux pump genes in response to the inactivation of single or multiple homologues was measured using real-time RT–PCR. Phenotypes of mutants were characterized by measuring antimicrobial susceptibility, dye accumulation and the ability to cause infection in vitro. Results The expression of all RND efflux pump genes was increased when single or multiple acr genes were inactivated, suggesting a feedback mechanism that activates the transcription of homologous efflux pump genes. When two or three acr genes were inactivated, the mutants had further reduced efflux, altered susceptibility to antimicrobials (including increased susceptibility to some, but conversely and counterintuitively, decreased susceptibility to some others) and were more attenuated in the tissue culture model than mutants lacking single pumps were. Conclusions These data indicate that it is critical to understand which pumps an inhibitor is active against and the effect of this on the expression of homologous systems. For some antimicrobials, an inhibitor with activity against multiple pumps will have a greater impact on susceptibility, but an unintended consequence of this may be decreased susceptibility to other drugs, such as aminoglycosides.
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Affiliation(s)
- Jessica M A Blair
- Antimicrobials Research Group, School of Immunity and Infection, College of Medical and Dental Sciences, and Institute of Microbiology and Infection, The University of Birmingham, Birmingham B15 2TT, UK
| | - Helen E Smith
- Antimicrobials Research Group, School of Immunity and Infection, College of Medical and Dental Sciences, and Institute of Microbiology and Infection, The University of Birmingham, Birmingham B15 2TT, UK
| | - Vito Ricci
- Antimicrobials Research Group, School of Immunity and Infection, College of Medical and Dental Sciences, and Institute of Microbiology and Infection, The University of Birmingham, Birmingham B15 2TT, UK
| | - Amelia J Lawler
- Antimicrobials Research Group, School of Immunity and Infection, College of Medical and Dental Sciences, and Institute of Microbiology and Infection, The University of Birmingham, Birmingham B15 2TT, UK
| | - Louisa J Thompson
- Antimicrobials Research Group, School of Immunity and Infection, College of Medical and Dental Sciences, and Institute of Microbiology and Infection, The University of Birmingham, Birmingham B15 2TT, UK
| | - Laura J V Piddock
- Antimicrobials Research Group, School of Immunity and Infection, College of Medical and Dental Sciences, and Institute of Microbiology and Infection, The University of Birmingham, Birmingham B15 2TT, UK
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Piddock LJV. Understanding the basis of antibiotic resistance: a platform for drug discovery. MICROBIOLOGY-SGM 2014; 160:2366-2373. [PMID: 25122880 DOI: 10.1099/mic.0.082412-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
There are numerous genes in Salmonella enterica serovar Typhimurium that can confer resistance to fluoroquinolone antibiotics, including those that encode topoisomerase proteins, the primary targets of this class of drugs. However, resistance is often multifactorial in clinical isolates and it is not uncommon to also detect mutations in genes that affect the expression of proteins involved in permeability and multi-drug efflux. The latter mechanism, mediated by tripartite efflux systems, such as that formed by the AcrAB-TolC system, confers inherent resistance to many antibiotics, detergents and biocides. Genetic inactivation of efflux genes gives multi-drug hyper-susceptibility, and in the absence of an intact AcrAB-TolC system some chromosomal and transmissible antibiotic resistance genes no longer confer clinically relevant levels of resistance. Furthermore, a functional multi-drug resistance efflux pump, such as AcrAB-TolC, is required for virulence and the ability to form a biofilm. In part, this is due to altered expression of virulence and biofilm genes being sensitive to efflux status. Efflux pump expression can be increased, usually due to mutations in regulatory genes, and this confers resistance to clinically useful drugs such as fluoroquinolones and β-lactams. Here, I discuss some of the work my team has carried out characterizing the mechanisms of antibiotic resistance in Salmonella enterica serovar Typhimurium from the late 1980s to 2014. A video of this Prize Lecture, presented at the Society for General Microbiology Annual Conference 2014, can be viewed via this link: https://www.youtube.com/watch?v=MCRumMV99Yw.
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Affiliation(s)
- Laura J V Piddock
- Antimicrobials Research Group, School of Immunity and Infection and Institute for Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, UK
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De Majumdar S, Yu J, Spencer J, Tikhonova IG, Schneiders T. Molecular basis of non-mutational derepression of ramA in Klebsiella pneumoniae. J Antimicrob Chemother 2014; 69:2681-9. [PMID: 25140579 DOI: 10.1093/jac/dku203] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
OBJECTIVES The ram locus, consisting of the romA-ramA genes, is repressed by the tetracycline-type regulator RamR, where regulation is abolished due to loss-of-function mutations within the protein or ligand interactions. The aim of this study was to determine whether the phenothiazines (chlorpromazine and thioridazine) directly interact with RamR to derepress ramA expression. METHODS Quantitative real-time PCR analyses were performed to determine expression levels of the romA-ramA genes after exposure to the phenothiazines. Electrophoretic mobility shift assays (EMSAs) and in vitro transcription experiments were performed to show direct binding to and repression by RamR. Direct binding of the RamR protein to the phenothiazines was measured by fluorescence spectroscopy experiments and molecular docking models were generated using the RamR crystal structure. RESULTS Exposure to either chlorpromazine or thioridazine resulted in the up-regulation of the romA-ramA genes. EMSAs and in vitro transcription experiments demonstrated that both agents reduce/abolish binding and enhance transcription of the target PI promoter upstream of the ramR-romA genes in Klebsiella pneumoniae compared with RamR alone. Fluorescence spectroscopy measurements demonstrated that RamR directly binds both chlorpromazine and thioridazine with micromolar affinity. Molecular docking analyses using the RamR crystal structure demonstrated that the phenothiazines interact with RamR protein through contacts described for other ligands, in addition to forming unique strong polar interactions at positions D152 and K63. CONCLUSIONS These data demonstrate that phenothiazines can modulate loci linked to the microbe-drug response where RamR is an intracellular target for the phenothiazines, thus resulting in a transient non-mutational derepression of ramA concentrations.
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Affiliation(s)
- Shyamasree De Majumdar
- Centre for Infection and Immunity, Health Sciences Building, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7AE, UK
| | - Jing Yu
- Centre for Infection and Immunity, Health Sciences Building, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7AE, UK
| | - James Spencer
- School of Cellular and Molecular Medicine, Medical Sciences Building, University of Bristol, University Walk, Bristol BS18 1TD, UK
| | - Irina G Tikhonova
- Molecular Therapeutics, School of Pharmacy, Medical Biology Centre, Queen's University Belfast, Belfast BT9 7BL, Northern Ireland, UK
| | - Thamarai Schneiders
- Centre for Infection and Immunity, Health Sciences Building, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7AE, UK
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Baucheron S, Nishino K, Monchaux I, Canepa S, Maurel MC, Coste F, Roussel A, Cloeckaert A, Giraud E. Bile-mediated activation of the acrAB and tolC multidrug efflux genes occurs mainly through transcriptional derepression of ramA in Salmonella enterica serovar Typhimurium. J Antimicrob Chemother 2014; 69:2400-6. [PMID: 24816212 DOI: 10.1093/jac/dku140] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
OBJECTIVES In Salmonella Typhimurium, the genes encoding the AcrAB-TolC multidrug efflux system are mainly regulated by the ramRA locus, composed of the divergently transcribed ramA and ramR genes. The acrAB and tolC genes are transcriptionally activated by RamA, the gene for which is itself transcriptionally repressed by RamR. Previous studies have reported that bile induces acrAB in a ramA-dependent manner, but none provided evidence for an induction of ramA expression by bile. Therefore, the objective of this study was to clarify the regulatory mechanism by which bile activates acrAB and tolC. METHODS qRT-PCR was used to address the effects of bile (using choleate, an ox-bile extract) on the expression of ramA, ramR, acrB and tolC. Electrophoretic mobility shift assays and surface plasmon resonance experiments were used to measure the effect of bile on RamR binding to the ramA promoter (PramA) region. RESULTS We show that ramA is transcriptionally activated by bile and is strictly required for the bile-mediated activation of acrB and tolC. Additionally, bile is shown to specifically inhibit the binding of RamR to the PramA region, which overlaps the putative divergent ramR promoter, thereby explaining our observation that bile also activates ramR transcription. CONCLUSIONS We propose a regulation model whereby the bile-mediated activation of the acrAB and tolC multidrug efflux genes occurs mainly through the transcriptional derepression of the ramA activator gene.
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Affiliation(s)
- Sylvie Baucheron
- INRA, UMR1282 Infectiologie et Santé Publique, F-37380 Nouzilly, France Université François Rabelais de Tours, UMR1282 Infectiologie et Santé Publique, F-37000 Tours, France
| | - Kunihiko Nishino
- Laboratory of Microbiology and Infectious Diseases, Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, Japan
| | - Isabelle Monchaux
- INRA, UMR1282 Infectiologie et Santé Publique, F-37380 Nouzilly, France Université François Rabelais de Tours, UMR1282 Infectiologie et Santé Publique, F-37000 Tours, France
| | - Sylvie Canepa
- INRA, UMR7247, Plateforme d'Analyse Intégrative des Biomolécules et de Phénomique des Animaux d'Intérêt Bio-agronomique, Nouzilly, France
| | - Marie-Christine Maurel
- INRA, UMR7247, Plateforme d'Analyse Intégrative des Biomolécules et de Phénomique des Animaux d'Intérêt Bio-agronomique, Nouzilly, France
| | - Franck Coste
- Centre de Biophysique Moléculaire CNRS, UPR4301, Orléans, France
| | - Alain Roussel
- Centre de Biophysique Moléculaire CNRS, UPR4301, Orléans, France
| | - Axel Cloeckaert
- INRA, UMR1282 Infectiologie et Santé Publique, F-37380 Nouzilly, France Université François Rabelais de Tours, UMR1282 Infectiologie et Santé Publique, F-37000 Tours, France
| | - Etienne Giraud
- INRA, UMR1282 Infectiologie et Santé Publique, F-37380 Nouzilly, France Université François Rabelais de Tours, UMR1282 Infectiologie et Santé Publique, F-37000 Tours, France
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Ricci V, Blair JMA, Piddock LJV. RamA, which controls expression of the MDR efflux pump AcrAB-TolC, is regulated by the Lon protease. J Antimicrob Chemother 2013; 69:643-50. [PMID: 24169580 PMCID: PMC3922155 DOI: 10.1093/jac/dkt432] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES RamA regulates the AcrAB-TolC multidrug efflux system. Using Salmonella Typhimurium, we investigated the stability of RamA and its impact on antibiotic resistance. METHODS To detect RamA, we introduced ramA::3XFLAG::aph into plasmid pACYC184 and transformed this into Salmonella Typhimurium SL1344ramA::cat and lon::aph mutants. An N-terminus-deleted mutant [pACYC184ramA(Δ2-21)::3XFLAG::aph] in which the first 20 amino acids of RamA were deleted was also constructed. To determine the abundance and half-life of FLAG-tagged RamA, we induced RamA with chlorpromazine (50 mg/L) and carried out western blotting using anti-FLAG antibody. Susceptibility to antibiotics and phenotypic characterization of the lon mutant was also carried out. RESULTS We show that on removal of chlorpromazine, a known inducer of ramA, the abundance of RamA decreased to pre-induced levels. However, in cells lacking functional Lon, we found that the RamA protein was not degraded. We also demonstrated that the 21 amino acid residues of the RamA N-terminus are required for recognition by the Lon protease. Antimicrobial susceptibility and phenotypic tests showed that the lon mutant was more susceptible to fluoroquinolone antibiotics, was filamentous when observed by microscopy and grew poorly, but showed no difference in motility or the ability to form a biofilm. There was also no difference in the ability of the lon mutant to invade human intestinal cells (INT-407). CONCLUSIONS In summary, we show that the ATP-dependent Lon protease plays an important role in regulating the expression of RamA and therefore multidrug resistance via AcrAB-TolC in Salmonella Typhimurium.
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Affiliation(s)
- Vito Ricci
- Antimicrobials Research Group, School of Immunity and Infection and Institute of Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, UK
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Duval V, Lister IM. MarA, SoxS and Rob of Escherichia coli - Global regulators of multidrug resistance, virulence and stress response. ACTA ACUST UNITED AC 2013; 2:101-124. [PMID: 24860636 DOI: 10.6000/1927-3037.2013.02.03.2] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
Bacteria have a great capacity for adjusting their metabolism in response to environmental changes by linking extracellular stimuli to the regulation of genes by transcription factors. By working in a co-operative manner, transcription factors provide a rapid response to external threats, allowing the bacteria to survive. This review will focus on transcription factors MarA, SoxS and Rob in Escherichia coli, three members of the AraC family of proteins. These homologous proteins exemplify the ability to respond to multiple threats such as oxidative stress, drugs and toxic compounds, acidic pH, and host antimicrobial peptides. MarA, SoxS and Rob recognize similar DNA sequences in the promoter region of more than 40 regulatory target genes. As their regulons overlap, a finely tuned adaptive response allows E. coli to survive in the presence of different assaults in a co-ordinated manner. These regulators are well conserved amongst Enterobacteriaceae and due to their broad involvement in bacterial adaptation in the host, have recently been explored as targets to develop new anti-virulence agents. The regulators are also being examined for their roles in novel technologies such as biofuel production.
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Affiliation(s)
- Valérie Duval
- Center for Adaptation Genetics and Drug Resistance, Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111
| | - Ida M Lister
- Arietis Corporation, 650 Albany Street, Room 130, Boston, MA 02118
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