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Li XZ, Plésiat P, Nikaido H. The challenge of efflux-mediated antibiotic resistance in Gram-negative bacteria. Clin Microbiol Rev 2015; 28:337-418. [PMID: 25788514 PMCID: PMC4402952 DOI: 10.1128/cmr.00117-14] [Citation(s) in RCA: 899] [Impact Index Per Article: 99.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The global emergence of multidrug-resistant Gram-negative bacteria is a growing threat to antibiotic therapy. The chromosomally encoded drug efflux mechanisms that are ubiquitous in these bacteria greatly contribute to antibiotic resistance and present a major challenge for antibiotic development. Multidrug pumps, particularly those represented by the clinically relevant AcrAB-TolC and Mex pumps of the resistance-nodulation-division (RND) superfamily, not only mediate intrinsic and acquired multidrug resistance (MDR) but also are involved in other functions, including the bacterial stress response and pathogenicity. Additionally, efflux pumps interact synergistically with other resistance mechanisms (e.g., with the outer membrane permeability barrier) to increase resistance levels. Since the discovery of RND pumps in the early 1990s, remarkable scientific and technological advances have allowed for an in-depth understanding of the structural and biochemical basis, substrate profiles, molecular regulation, and inhibition of MDR pumps. However, the development of clinically useful efflux pump inhibitors and/or new antibiotics that can bypass pump effects continues to be a challenge. Plasmid-borne efflux pump genes (including those for RND pumps) have increasingly been identified. This article highlights the recent progress obtained for organisms of clinical significance, together with methodological considerations for the characterization of MDR pumps.
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Affiliation(s)
- Xian-Zhi Li
- Human Safety Division, Veterinary Drugs Directorate, Health Products and Food Branch, Health Canada, Ottawa, Ontario, Canada
| | - Patrick Plésiat
- Laboratoire de Bactériologie, Faculté de Médecine-Pharmacie, Centre Hospitalier Régional Universitaire, Université de Franche-Comté, Besançon, France
| | - Hiroshi Nikaido
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
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Zheng J, Tian F, Cui S, Song J, Zhao S, Brown EW, Meng J. Differential gene expression by RamA in ciprofloxacin-resistant Salmonella Typhimurium. PLoS One 2011; 6:e22161. [PMID: 21811569 PMCID: PMC3139621 DOI: 10.1371/journal.pone.0022161] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Accepted: 06/16/2011] [Indexed: 11/22/2022] Open
Abstract
Overexpression of ramA has been implicated in resistance to multiple drugs in several enterobacterial pathogens. In the present study, Salmonella Typhimurium strain LTL with constitutive expression of ramA was compared to its ramA-deletion mutant by employing both DNA microarrays and phenotype microarrays (PM). The mutant strain with the disruption of ramA showed differential expression of at least 33 genes involved in 11 functional groups. The study confirmed at the transcriptional level that the constitutive expression of ramA was directly associated with increased expression of multidrug efflux pump AcrAB-TolC and decreased expression of porin protein OmpF, thereby conferring multiple drug resistance phenotype. Compared to the parent strain constitutively expressing ramA, the ramA mutant had increased susceptibility to over 70 antimicrobials and toxic compounds. The PM analysis also uncovered that the ramA mutant was better in utilization of 10 carbon sources and 5 phosphorus sources. This study suggested that the constitutive expression of ramA locus regulate not only multidrug efflux pump and accessory genes but also genes involved in carbon metabolic pathways.
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Affiliation(s)
- Jie Zheng
- Joint Institute for Food Safety and Applied Nutrition, and Department of Nutrition and Food Science, University of Maryland, College Park, Maryland, United States of America
- Center for Food Safety & Applied Nutrition, U.S. Food & Drug Administration, Maryland, University of Maryland, College Park, Maryland, United States of America
| | - Fei Tian
- Department of Animal and Avian Science, University of Maryland, College Park, Maryland, United States of America
| | - Shenghui Cui
- State Food and Drug Administration, Beijing, China
| | - Jiuzhou Song
- Department of Animal and Avian Science, University of Maryland, College Park, Maryland, United States of America
| | - Shaohua Zhao
- Center for Veterinary Medicine, U.S. Food and Drug Administration, Maryland, University of Maryland, College Park, Maryland, United States of America
| | - Eric W. Brown
- Center for Food Safety & Applied Nutrition, U.S. Food & Drug Administration, Maryland, University of Maryland, College Park, Maryland, United States of America
| | - Jianghong Meng
- Joint Institute for Food Safety and Applied Nutrition, and Department of Nutrition and Food Science, University of Maryland, College Park, Maryland, United States of America
- * E-mail:
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3
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Allen HK, Cloud-Hansen KA, Wolinski JM, Guan C, Greene S, Lu S, Boeyink M, Broderick NA, Raffa KF, Handelsman J. Resident microbiota of the gypsy moth midgut harbors antibiotic resistance determinants. DNA Cell Biol 2010; 28:109-17. [PMID: 19206998 DOI: 10.1089/dna.2008.0812] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Little is known about the significance of insects as environmental reservoirs of antibiotic-resistant bacteria. We characterized the antibiotic resistome of the microbial community in gypsy moth larval midguts by applying functional metagenomics to cultured isolates. The minimum inhibitory concentrations of 12 antibiotics were determined for 44 cultured isolates, and antibiotic resistance genes were selected from metagenomic libraries derived from DNA extracted from a pool of the isolates. Six unique clones were identified. Two were highly resistant to penicillin-type beta-lactams, two were moderately resistant to erythromycin, and two were moderately resistant to a range of antibiotics, including erythromycin, carbenicillin, and chloramphenicol. Sequence analysis predicted that the active genes encoded efflux pumps, a transcriptional activator of efflux pump protein expression, and an extended-spectrum class A beta-lactamase. Insect guts are a reservoir of antibiotic resistance genes with the potential for dissemination.
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Affiliation(s)
- Heather K Allen
- Departments of Bacteriology and Plant Pathology, University of Wisconsin, Madison, Wisconsin, USA
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4
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Nishino K, Nikaido E, Yamaguchi A. Regulation and physiological function of multidrug efflux pumps in Escherichia coli and Salmonella. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2009; 1794:834-43. [DOI: 10.1016/j.bbapap.2009.02.002] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2008] [Revised: 02/02/2009] [Accepted: 02/05/2009] [Indexed: 01/30/2023]
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Naesens R, Ursi JP, Van Schaeren J, Jeurissen A. In vitro activity of tigecycline against multidrug-resistant Enterobacteriaceae isolates from a Belgian hospital. Eur J Clin Microbiol Infect Dis 2008; 28:381-4. [PMID: 18802728 DOI: 10.1007/s10096-008-0629-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2008] [Accepted: 08/27/2008] [Indexed: 11/28/2022]
Abstract
Bacterial resistance among Gram-negative pathogens is a challenging clinical problem. Tigecycline has been developed specifically to overcome resistance. The aim of this study was to assess the in vitro activity of tigecycline against ESBL-producing Escherichia coli, ESBL-producing Klebsiella spp., and multidrug-resistant Enterobacter spp. Between May 2007 and March 2008, 26 strains of ESBL-producing Escherichia coli, 10 strains of ESBL-producing Klebsiella spp., and 27 strains of multidrug-resistant Enterobacter spp. were isolated consecutively from inpatients with a documented infection in which the collected isolate was identified as the probable causative organism. The in vitro susceptibility against tigecycline was measured by the E-test method. MIC(50) values were 1 microg/ml, 2 microg/ml, and 3 microg/ml respectively. MIC(90) values were respectively 1.5 microg/ml, 4 microg/ml, and 12 microg/ml. Nonsusceptibility rates of 35%, 100%, and 96% respectively were found using EUCAST breakpoints. Despite the limited number of strains tested, our in vitro data suggest that tigecycline is unsuitable for the treatment of infections with multidrug-resistant Enterobacteriaceae in our setting. Therefore, we suggest that larger multicenter studies should be conducted to reconsider the value of tigecycline for the treatment of infections with multidrug-resistant, Gram-negative bacteria.
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Fouts DE, Tyler HL, DeBoy RT, Daugherty S, Ren Q, Badger JH, Durkin AS, Huot H, Shrivastava S, Kothari S, Dodson RJ, Mohamoud Y, Khouri H, Roesch LFW, Krogfelt KA, Struve C, Triplett EW, Methé BA. Complete genome sequence of the N2-fixing broad host range endophyte Klebsiella pneumoniae 342 and virulence predictions verified in mice. PLoS Genet 2008; 4:e1000141. [PMID: 18654632 PMCID: PMC2453333 DOI: 10.1371/journal.pgen.1000141] [Citation(s) in RCA: 180] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Accepted: 06/24/2008] [Indexed: 12/25/2022] Open
Abstract
We report here the sequencing and analysis of the genome of the nitrogen-fixing endophyte, Klebsiella pneumoniae 342. Although K. pneumoniae 342 is a member of the enteric bacteria, it serves as a model for studies of endophytic, plant-bacterial associations due to its efficient colonization of plant tissues (including maize and wheat, two of the most important crops in the world), while maintaining a mutualistic relationship that encompasses supplying organic nitrogen to the host plant. Genomic analysis examined K. pneumoniae 342 for the presence of previously identified genes from other bacteria involved in colonization of, or growth in, plants. From this set, approximately one-third were identified in K. pneumoniae 342, suggesting additional factors most likely contribute to its endophytic lifestyle. Comparative genome analyses were used to provide new insights into this question. Results included the identification of metabolic pathways and other features devoted to processing plant-derived cellulosic and aromatic compounds, and a robust complement of transport genes (15.4%), one of the highest percentages in bacterial genomes sequenced. Although virulence and antibiotic resistance genes were predicted, experiments conducted using mouse models showed pathogenicity to be attenuated in this strain. Comparative genomic analyses with the presumed human pathogen K. pneumoniae MGH78578 revealed that MGH78578 apparently cannot fix nitrogen, and the distribution of genes essential to surface attachment, secretion, transport, and regulation and signaling varied between each genome, which may indicate critical divergences between the strains that influence their preferred host ranges and lifestyles (endophytic plant associations for K. pneumoniae 342 and presumably human pathogenesis for MGH78578). Little genome information is available concerning endophytic bacteria. The K. pneumoniae 342 genome will drive new research into this less-understood, but important category of bacterial-plant host relationships, which could ultimately enhance growth and nutrition of important agricultural crops and development of plant-derived products and biofuels.
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Nikaido E, Yamaguchi A, Nishino K. AcrAB multidrug efflux pump regulation in Salmonella enterica serovar Typhimurium by RamA in response to environmental signals. J Biol Chem 2008; 283:24245-53. [PMID: 18577510 PMCID: PMC2527123 DOI: 10.1074/jbc.m804544200] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Salmonella enterica serovar Typhimurium has at least nine
multidrug efflux pumps. Among these pumps, AcrAB is effective in generating
drug resistance and has wide substrate specificity. Here we report that
indole, bile, and an Escherichia coli conditioned medium induced the
AcrAB pump in Salmonella through a specific regulator, RamA. The
RamA-binding sites were located in the upstream regions of acrAB and
tolC. RamA was required for indole induction of acrAB. Other
regulators of acrAB such as MarA, SoxS, Rob, SdiA, and AcrR did not
contribute to acrAB induction by indole in Salmonella.
Indole activated ramA transcription, and overproduction of RamA
caused increased acrAB expression. In contrast, induction of
ramA was not required for induction of acrAB by bile. Cholic
acid binds to RamA, and we suggest that bile acts by altering pre-existing
RamA. This points to two different AcrAB regulatory modes through RamA. Our
results suggest that RamA controls the Salmonella AcrAB-TolC
multidrug efflux system through dual regulatory modes in response to
environmental signals.
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Affiliation(s)
- Eiji Nikaido
- Department of Cell Membrane Biology, Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
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8
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Keeney D, Ruzin A, Bradford PA. RamA, a Transcriptional Regulator, and AcrAB, an RND-Type Efflux Pump, are Associated with Decreased Susceptibility to Tigecycline inEnterobacter cloacae. Microb Drug Resist 2007; 13:1-6. [PMID: 17536927 DOI: 10.1089/mdr.2006.9990] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Tigecycline, a novel broad-spectrum glycylcycline antibiotic, is active against many gram-positive and gram-negative bacterial pathogens including most strains of Enterobacter cloacae. Recently, however, a few clinical strains of E. cloacae with decreased susceptibility to tigecycline were isolated. In this study, two tigecycline-susceptible mutants of E. cloacae, GC7696 and GC7697, were obtained by transposon mutagenesis of a tigecycline-resistant clinical isolate G946. Transposon insertions were mapped to either the acrA or acrB genes. Restoration of the original resistant phenotype occurred when GC7696 and GC7697 were transcomplemented with a plasmid harboring the intact acrAB region amplified from G946. Northern blot analysis of G946 and several other E. cloacae clinical strains that exhibited decreased susceptibility to tigecycline, revealed increased levels of the acrAB transcript. In addition, overexpression of acrAB correlated with increased expression of the ramA gene, whereas the expression of another transcriptional activator, marA, was not changed. These results suggest that decreased susceptibility to tigecycline in E. cloacae is the result of RamA-mediated overexpression of the AcrAB efflux pump.
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Affiliation(s)
- David Keeney
- Department of Infectious Disease, Wyeth Research, 401 North Middletown Road, Pearl River, NY 10965, USA.
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9
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Ruzin A, Visalli MA, Keeney D, Bradford PA. Influence of transcriptional activator RamA on expression of multidrug efflux pump AcrAB and tigecycline susceptibility in Klebsiella pneumoniae. Antimicrob Agents Chemother 2005; 49:1017-22. [PMID: 15728897 PMCID: PMC549240 DOI: 10.1128/aac.49.3.1017-1022.2005] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Tigecycline is an expanded broad-spectrum antibacterial agent that is active against many clinically relevant species of bacterial pathogens, including Klebsiella pneumoniae. The majority of K. pneumoniae isolates are fully susceptible to tigecycline; however, a few strains that have decreased susceptibility have been isolated. One isolate, G340 (for which the tigecycline MIC is 4 microg/ml and which displays a multidrug resistance [MDR] phenotype), was selected for analysis of the mechanism for this decreased susceptibility by use of transposon mutagenesis with IS903phikan. A tigecycline-susceptible mutant of G340, GC7535, was obtained (tigecycline MIC, 0.25 microg/ml). Analysis of the transposon insertion mapped it to ramA, a gene that was previously identified to be involved in MDR in K. pneumoniae. For GC7535, the disruption of ramA led to a 16-fold decrease in the MIC of tigecycline and also a suppression of MDR. Trans-complementation with plasmid-borne ramA restored the original parental phenotype of decreased susceptibility to tigecycline. Northern blot analysis revealed a constitutive overexpression of ramA that correlated with an increased expression of the AcrAB transporter in G340 compared to that in tigecycline-susceptible strains. Laboratory mutants of K. pneumoniae with decreased susceptibility to tigecycline could be selected at a frequency of approximately 4 x 10(-8). These results suggest that ramA is associated with decreased tigecycline susceptibility in K. pneumoniae due to its role in the expression of the AcrAB multidrug efflux pump.
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Affiliation(s)
- Alexey Ruzin
- Wyeth Research, Department of Infectious Disease, 401 North Middletown Rd., Bldg. 200, Rm. 3219, Pearl River, NY 10965, USA.
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10
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Yassien MA, Ewis HE, Lu CD, Abdelal AT. Molecular cloning and characterization of the Salmonella enterica Serovar Paratyphi B rma Gene, which confers multiple drug resistance in Escherichia coli. Antimicrob Agents Chemother 2002; 46:360-6. [PMID: 11796342 PMCID: PMC127067 DOI: 10.1128/aac.46.2.360-366.2002] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A genomic library from a strain of Salmonella enterica serovar Paratyphi B that exhibits multiple drug resistance (MDR) was constructed in Escherichia coli. Two of the recombinant plasmids, pNOR5 and pNOR5, conferred resistance only to fluoroquinolones in E. coli, whereas the third, pNCTR4, conferred the MDR phenotype. Sequence and subcloning analysis showed that it is the presence of RecA on the first two plasmids which confers resistance to fluoroquinolones in E. coli. A similar analysis established that the MDR phenotype conferred by pNCTR4 is due to a gene, rma (resistance to multiple antibiotics), which encodes a 13.5-kDa polypeptide. The derived sequence for Rma exhibits a high degree of similarity to those of a group of MarA-like activators that confer MDR in E. coli. A MalE-Rma fusion protein was purified to near homogeneity and was shown to interact with a DNA fragment carrying a MarA operator sequence. Furthermore, overexpression of rma in E. coli caused changes in the outer membrane protein profile that were similar to those reported for MarA. These results suggest that Rma might act as a transcriptional activator of the marA regulon.
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Affiliation(s)
- Mahmoud A Yassien
- Department of Microbiology and Immunology, Faculty of Pharmacy, Ain-Shams University, Cairo, Egypt
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11
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He J, Magarvey N, Piraee M, Vining LC. The gene cluster for chloramphenicol biosynthesis in Streptomyces venezuelae ISP5230 includes novel shikimate pathway homologues and a monomodular non-ribosomal peptide synthetase gene. MICROBIOLOGY (READING, ENGLAND) 2001; 147:2817-2829. [PMID: 11577160 DOI: 10.1099/00221287-147-10-2817] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Regions of the Streptomyces venezuelae ISP5230 chromosome flanking pabAB, an amino-deoxychorismate synthase gene needed for chloramphenicol (Cm) production, were examined for involvement in biosynthesis of the antibiotic. Three of four ORFs in the sequence downstream of pabAB resembled genes involved in the shikimate pathway. BLASTX searches of GenBank showed that the deduced amino acid sequences of ORF3 and ORF4 were similar to proteins encoded by monofunctional genes for chorismate mutase and prephenate dehydrogenase, respectively, while the sequence of the ORF5 product resembled deoxy-arabino-heptulosonate-7-phosphate (DAHP) synthase, the enzyme that initiates the shikimate pathway. A relationship to Cm biosynthesis was indicated by sequence similarities between the ORF6 product and membrane proteins associated with Cm export. BLASTX searches of GenBank for matches with the translated sequence of ORF1 in chromosomal DNA immediately upstream of pabAB did not detect products relevant to Cm biosynthesis. However, the presence of Cm biosynthesis genes in a 7.5 kb segment of the chromosome beyond ORF1 was inferred when conjugal transfer of the DNA into a blocked S. venezuelae mutant restored Cm production. Deletions in the 7.5 kb segment of the wild-type chromosome eliminated Cm production, confirming the presence of Cm biosynthesis genes in this region. Sequencing and analysis located five ORFs, one of which (ORF8) was deduced from BLAST searches of GenBank, and from characteristic motifs detected in alignments of its deduced amino acid sequence, to be a monomodular nonribosomal peptide synthetase. GenBank searches did not identify ORF7, but matched the translated sequences of ORFs 9, 10 and 11 with short-chain ketoreductases, the ATP-binding cassettes of ABC transporters, and coenzyme A ligases, respectively. As has been shown for ORF2, disrupting ORF3, ORF7, ORF8 or ORF9 blocked Cm production.
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Affiliation(s)
- J He
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, CanadaB3H 4J11
| | - N Magarvey
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, CanadaB3H 4J11
| | - M Piraee
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, CanadaB3H 4J11
| | - L C Vining
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, CanadaB3H 4J11
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12
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Daiyasu H, Osaka K, Ishino Y, Toh H. Expansion of the zinc metallo-hydrolase family of the beta-lactamase fold. FEBS Lett 2001; 503:1-6. [PMID: 11513844 DOI: 10.1016/s0014-5793(01)02686-2] [Citation(s) in RCA: 258] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recently, the zinc metallo-hydrolase family of the beta-lactamase fold has grown quite rapidly, accompanied by the accumulation of sequence and structure data. The variety of the biological functions of the family is higher than expected. In addition, the members often have mosaic structures with additional domains. The family includes class B beta-lactamase, glyoxalase II, arylsulfatase, flavoprotein, cyclase/dehydrase, an mRNA 3'-processing protein, a DNA cross-link repair enzyme, a DNA uptake-related protein, an alkylphosphonate uptake-related protein, CMP-N-acetylneuraminate hydroxylase, the romA gene product, alkylsulfatase, and insecticide hydrolases. In this minireview, the functional and structural varieties of the growing protein family are described.
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Affiliation(s)
- H Daiyasu
- Department of Bioinformatics, Biomolecular Engineering Research Institute, Osaka, Japan
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Alekshun MN, Levy SB. Regulation of chromosomally mediated multiple antibiotic resistance: the mar regulon. Antimicrob Agents Chemother 1997; 41:2067-75. [PMID: 9333027 PMCID: PMC164072 DOI: 10.1128/aac.41.10.2067] [Citation(s) in RCA: 358] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Affiliation(s)
- M N Alekshun
- Center for Adaptation Genetics and Drug Resistance and the Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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14
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Lee EH, Collatz E, Podglajen I, Gutmann L. A rob-like gene of Enterobacter cloacae affecting porin synthesis and susceptibility to multiple antibiotics. Antimicrob Agents Chemother 1996; 40:2029-33. [PMID: 8878575 PMCID: PMC163467 DOI: 10.1128/aac.40.9.2029] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
A chromosomal gene of Enterobacter cloacae affecting the synthesis of major outer membrane proteins in E. cloacae and Escherichia coli was cloned by using selection for resistance to cefoxitin in E. coli. The presence of the gene, when plasmid-borne, led to a decrease in the amount of porin F in E. cloacae and the amount of OmpF in E. coli and caused 2- to 32-fold increases in the MICs of chloramphenicol, tetracycline, quinolones, and beta-lactam antibiotics. The gene encoded a 33-kDa protein, similar (83% identity) to the protein Rob involved in the initiation of DNA replication in E. coli, which was called RobA(EC1) by analogy. RobA from E. cloacae was found to inhibit ompF expression at the posttranscriptional level via activation of micF, a gene also apparently present in E. cloacae, as detected by PCR. As with its homolog from E. coli, RobA(EC1) is related to the XylS-AraC class of positive transcriptional regulators, along with MarA and SoxS, which also cause a micF-mediated decrease in the level of ampF expression.
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Affiliation(s)
- E H Lee
- Laboratoire de Recherche Moléculaire sur les Antibiotiques, Université Paris VI, France
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15
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Abstract
In Gram-negative bacteria, multidrug resistance is a term that is used to describe mechanisms of resistance by chromosomal genes that are activated by induction or mutation caused by the stress of exposure to antibiotics in natural and clinical environments. Unlike plasmid-borne resistance genes, there is no alteration or degradation of drugs or need for genetic transfer. Exposure to a single drug leads to cross-resistance to many other structurally and functionally unrelated drugs. The only mechanism identified for multidrug resistance in bacteria is drug efflux by membrane transporters, even though many of these transporters remain to be identified. The enteric bacteria exhibit mostly complex multidrug resistance systems which are often regulated by operons or regulons. The purpose of this review is to survey molecular mechanisms of multidrug resistance in enteric and other Gram-negative bacteria, and to speculate on the origins and natural physiological functions of the genes involved.
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Affiliation(s)
- A M George
- Department of Cell and Molecular Biology, University of Technology Sydney, NSW, Australia.
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16
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George AM, Hall RM, Stokes HW. Multidrug resistance in Klebsiella pneumoniae: a novel gene, ramA, confers a multidrug resistance phenotype in Escherichia coli. MICROBIOLOGY (READING, ENGLAND) 1995; 141 ( Pt 8):1909-1920. [PMID: 7551053 DOI: 10.1099/13500872-141-8-1909] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Spontaneous multidrug-resistant (Mdr) mutants of Klebsiella pneumoniae strain ECL8 arose at a frequency of 2.2 x 10(-8) and showed increased resistance to a range of unrelated antibiotics, including chloramphenicol, tetracycline, nalidixic acid, ampicillin, norfloxacin, trimethoprim and puromycin. A chromosomal fragment from one such mutant was cloned, and found to confer an Mdr phenotype on Escherichia coli K12 cells that was essentially identical to that of the K. pneumoniae mutant. Almost complete loss of the OmpF porin in the E. coli transformant, and of the corresponding porin in the K. pneumoniae mutant, was observed. The presence of the Mdr mutation in K. pneumoniae or the cloned K. pneumoniae ramA (resistance antibiotic multiple) locus in E. coli also resulted in active efflux of tetracycline, and increased active efflux of chloramphenicol. After transformation of a ramA plasmid into E. coli, expression of chloramphenicol resistance occurred later than expression of resistance to tetracycline, puromycin, trimethoprim and nalidixic acid. The ramA gene was localized and sequenced. It encodes a putative positive transcriptional activator that is weakly related to the E. coli MarA and SoxS proteins. A ramA gene was also found to be present in an Enterobacter cloacae fragment that has previously been shown to confer an Mdr phenotype, and it appears that ramA, rather than the romA gene identified in that study, is responsible for multidrug resistance. The ramA gene from the wild-type K. pneumoniae was identical to that of the mutant strain and also conferred an Mdr phenotype on E. coli, indicating that the mutation responsible for Mdr in K. pneumoniae had not been cloned.
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Affiliation(s)
- Anthony M George
- Department of Biochemistry and Physiology, University of Technology Sydney, PO Box 123, Broadway NSW 2007, Australia
| | - Ruth M Hall
- CSIRO Division of Biomolecular Engineering, Laboratory for Molecular Biology, PO Box 184, North Ryde NSW 2113, Australia
| | - H W Stokes
- School of Biological Sciences, Macquarie University, Sydney NSW 2109, Australia
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17
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Komatsu T, Ohta M, Kido N, Arakawa Y, Ito H, Kato N. Increased resistance to multiple drugs by introduction of the Enterobacter cloacae romA gene into OmpF porin-deficient mutants of Escherichia coli K-12. Antimicrob Agents Chemother 1991; 35:2155-8. [PMID: 1662028 PMCID: PMC245346 DOI: 10.1128/aac.35.10.2155] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Introduction of the romA gene cloned from Enterobacter cloacae into Escherichia coli K-12 resulted in almost complete inhibition of OmpF expression and a concomitant increase in resistance to quinolones, beta-lactams, chloramphenicol, and tetracyclines. In addition, the romA gene reduced the susceptibility to these multiple drugs even in the OmpF porin-deficient mutants of E. coli K-12. Results indicate the presence of romA-sensitive penetration pathway(s) for these multiple drugs other than the OmpF porin in E. coli.
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Affiliation(s)
- T Komatsu
- Department of Bacteriology, Nagoya University School of Medicine, Aichi, Japan
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Bissonnette L, Champetier S, Buisson JP, Roy PH. Characterization of the nonenzymatic chloramphenicol resistance (cmlA) gene of the In4 integron of Tn1696: similarity of the product to transmembrane transport proteins. J Bacteriol 1991; 173:4493-502. [PMID: 1648560 PMCID: PMC208113 DOI: 10.1128/jb.173.14.4493-4502.1991] [Citation(s) in RCA: 136] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Integrons constitute a novel family of DNA elements which evolved by site-specific integration of discrete units between two conserved segments. On the In4 integron of Tn1696, a precisely inserted gene cassette of 1,549 bp conferring nonenzymatic chloramphenicol resistance (cmlA) is present between the streptomycin-spectinomycin resistance (aadA2) gene cassette and the 3'-conserved segment of the integron. In this study, we present the nucleotide sequence of the cmlA gene cassette of Tn1696, show its similarity to bacterial efflux systems and other transport proteins, and present evidence for alterations that its expression exerts on bacterial membranes. The cmlA gene cassette apparently carries its own promoter(s), a situation that has not heretofore been observed in the integrons of multiresistance plasmids and transposons of gram-negative bacteria. One or more of these promoters were shown to be functionally active in expressing a cat marker gene from promoter-probe vectors. The putative CmlA polypeptide appears to provoke a reduction of the content of the major porins OmpA and OmpC.
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Affiliation(s)
- L Bissonnette
- Département de Biochimie, Faculté des Sciences et de Génie, Université Laval, Sainte-Foy, Québec, Canada
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Bellido F, Pechère JC, Hancock RE. Novel method for measurement of outer membrane permeability to new beta-lactams in intact Enterobacter cloacae cells. Antimicrob Agents Chemother 1991; 35:68-72. [PMID: 2014983 PMCID: PMC244943 DOI: 10.1128/aac.35.1.68] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The ability of five new beta-lactams to permeate the outer membrane of intact Enterobacter cloacae beta-lactamase-overproducing cells was measured by using a high-pressure liquid chromatography (HPLC)-based technique that avoided certain possible artifacts of the traditional methods. Low concentrations of antibiotics were mixed with bacterial suspensions, and at different times, the cells were removed from the medium by filtration. Residual beta-lactam concentrations in the medium were then assessed by HPLC and UV detection. The assay was performed under conditions in which no beta-lactamase activity was detected in the filtrate and the number of viable cells remained constant during the experiment. Outer membrane permeability was assessed with the Zimmermann-Rosselet equation, in which outer membrane permeability was rate limiting for hydrolysis of the beta-lactam by periplasmic beta-lactamase. Thus, the rate of disappearance of beta-lactam was equal to the rate of outer membrane permeation. Preincubation of bacterial suspensions with 300 micrograms of cloxacillin per ml inhibited the hydrolysis of beta-lactams by intact cells, demonstrating that beta-lactam hydrolysis by periplasmic beta-lactamase was essential in order to allow measurement of outer membrane permeability by this method. Permeability coefficients (P) were calculated from the Zimmermann-Rosselet equation and were independent of the external concentration of antibiotic over a 100-fold concentration range. Cefepime and cefpirome exhibited rates of outer membrane permeation 5- to 20-fold higher than those of carumonam, ceftriaxone, and cefotaxime. Thus, the presence of a positive charge in the 3-lateral chain increased the permeation ability of beta-lactam molecules considerably.
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Affiliation(s)
- F Bellido
- Department of Microbiology, University of British Columbia, Vancouver, Canada
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