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Gauthier J, Kukavica-Ibrulj I, Cockenpot L, Mohit V, Bernier J, Brisson C, Levesque RC. Complete genome sequence of multidrug-resistant Enterobacter roggenkampii 0-E. Microbiol Resour Announc 2024; 13:e0114923. [PMID: 38299819 DOI: 10.1128/mra.01149-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Accepted: 01/18/2024] [Indexed: 02/02/2024] Open
Abstract
Here, we present the complete 4.77 Mb genome of Enterobacter roggenkampii 0-E assembled with Oxford Nanopore long reads. This genome harbors 19 antimicrobial resistance genes, including ramA and marA decreasing permeability to carbapenems. This genome adds novel knowledge on emerging multidrug resistance in the Enterobacter cloacae species complex.
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Affiliation(s)
- Jeff Gauthier
- Institut de biologie intégrative et des systèmes (IBIS), Faculté de médecine, Université Laval, Québec, Canada
| | - Irena Kukavica-Ibrulj
- Institut de biologie intégrative et des systèmes (IBIS), Faculté de médecine, Université Laval, Québec, Canada
| | - Laure Cockenpot
- Direction Générale de la coordination scientifique et du Centre d'expertise en analyse environnementale du Québec (DGCSCEAEQ); Ministère de l'Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs (MELCCFP), Québec, Canada
| | - Vani Mohit
- Direction Générale de la coordination scientifique et du Centre d'expertise en analyse environnementale du Québec (DGCSCEAEQ); Ministère de l'Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs (MELCCFP), Québec, Canada
| | - Jimmy Bernier
- Direction Générale de la coordination scientifique et du Centre d'expertise en analyse environnementale du Québec (DGCSCEAEQ); Ministère de l'Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs (MELCCFP), Québec, Canada
| | - Chantal Brisson
- Direction Générale de la coordination scientifique et du Centre d'expertise en analyse environnementale du Québec (DGCSCEAEQ); Ministère de l'Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs (MELCCFP), Québec, Canada
| | - Roger C Levesque
- Institut de biologie intégrative et des systèmes (IBIS), Faculté de médecine, Université Laval, Québec, Canada
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Rodrigues SH, Nunes GD, Soares GG, Ferreira RL, Damas MSF, Laprega PM, Shilling RE, Campos LC, da Costa AS, Malavazi I, da Cunha AF, Pranchevicius MCDS. First report of coexistence of blaKPC-2 and blaNDM-1 in carbapenem-resistant clinical isolates of Klebsiella aerogenes in Brazil. Front Microbiol 2024; 15:1352851. [PMID: 38426065 PMCID: PMC10903355 DOI: 10.3389/fmicb.2024.1352851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2023] [Accepted: 01/26/2024] [Indexed: 03/02/2024] Open
Abstract
Klebsiella aerogenes is an important opportunistic pathogen with the potential to develop resistance against last-line antibiotics, such as carbapenems, limiting the treatment options. Here, we investigated the antibiotic resistance profiles of 10 K. aerogenes strains isolated from patient samples in the intensive-care unit of a Brazilian tertiary hospital using conventional PCR and a comprehensive genomic characterization of a specific K. aerogenes strain (CRK317) carrying both the blaKPC-2 and blaNDM-1 genes simultaneously. All isolates were completely resistant to β-lactam antibiotics, including ertapenem, imipenem, and meropenem with differencing levels of resistance to aminoglycosides, quinolones, and tigecycline also observed. Half of the strains studied were classified as multidrug-resistant. The carbapenemase-producing isolates carried many genes of interest including: β-lactams (blaNDM-1, blaKPC-2, blaTEM-1, blaCTX-M-1 group, blaOXA-1 group and blaSHVvariants in 20-80% of the strains), aminoglycoside resistance genes [aac(6')-Ib and aph(3')-VI, 70 and 80%], a fluoroquinolone resistance gene (qnrS, 80%), a sulfonamide resistance gene (sul-2, 80%) and a multidrug efflux system transporter (mdtK, 70%) while all strains carried the efflux pumps Acr (subunit A) and tolC. Moreover, we performed a comprehensive genomic characterization of a specific K. aerogenes strain (CRK317) carrying both the blaKPC-2 and blaNDM-1 genes simultaneously. The draft genome assembly of the CRK317 had a total length of 5,462,831 bp and a GC content of 54.8%. The chromosome was found to contain many essential genes. In silico analysis identified many genes associated with resistance phenotypes, including β-lactamases (blaOXA-9, blaTEM-1, blaNDM-1, blaCTX-M-15, blaAmpC-1, blaAmpC-2), the bleomycin resistance gene (bleMBL), an erythromycin resistance methylase (ermC), aminoglycoside-modifying enzymes [aac(6')-Ib, aadA/ant(3")-Ia, aph(3')-VI], a sulfonamide resistance enzyme (sul-2), a chloramphenicol acetyltransferase (catA-like), a plasmid-mediated quinolone resistance protein (qnrS1), a glutathione transferase (fosA), PEtN transferases (eptA, eptB) and a glycosyltransferase (arnT). We also detected 22 genomic islands, eight families of insertion sequences, two putative integrative and conjugative elements with a type IV secretion system, and eight prophage regions. This suggests the significant involvement of these genetic structures in the dissemination of antibiotic resistance. The results of our study show that the emergence of carbapenemase-producing K. aerogenes, co-harboring blaKPC-2 and blaNDM-1, is a worrying phenomenon which highlights the importance of developing strategies to detect, prevent, and control the spread of these microorganisms.
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Affiliation(s)
- Saulo Henrique Rodrigues
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil
| | - Gustavo Dantas Nunes
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil
| | - Gabriela Guerrera Soares
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil
| | - Roumayne Lopes Ferreira
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil
| | | | - Pedro Mendes Laprega
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil
| | | | | | - Andrea Soares da Costa
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil
| | - Iran Malavazi
- Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, São Paulo, Brazil
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Ferrando N, Pino-Otín MR, Ballestero D, Lorca G, Terrado EM, Langa E. Enhancing Commercial Antibiotics with Trans-Cinnamaldehyde in Gram-Positive and Gram-Negative Bacteria: An In Vitro Approach. PLANTS (BASEL, SWITZERLAND) 2024; 13:192. [PMID: 38256746 PMCID: PMC10820649 DOI: 10.3390/plants13020192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 12/21/2023] [Accepted: 01/05/2024] [Indexed: 01/24/2024]
Abstract
One strategy to mitigate the emergence of bacterial resistance involves reducing antibiotic doses by combining them with natural products, such as trans-cinnamaldehyde (CIN). The objective of this research was to identify in vitro combinations (CIN + commercial antibiotic (ABX)) that decrease the minimum inhibitory concentration (MIC) of seven antibiotics against 14 different Gram-positive and Gram-negative pathogenic bacteria, most of them classified as ESKAPE. MIC values were measured for all compounds using the broth microdilution method. The effect of the combinations on these microorganisms was analyzed through the checkboard assay to determine the type of activity (synergy, antagonism, or addition). This analysis was complemented with a kinetic study of the synergistic combinations. Fifteen synergistic combinations were characterized for nine of the tested bacteria. CIN demonstrated effectiveness in reducing the MIC of chloramphenicol, streptomycin, amoxicillin, and erythromycin (94-98%) when tested on Serratia marcescens, Staphylococcus aureus, Pasteurella aerogenes, and Salmonella enterica, respectively. The kinetic study revealed that when the substances were tested alone at the MIC concentration observed in the synergistic combination, bacterial growth was not inhibited. However, when CIN and the ABX, for which synergy was observed, were tested simultaneously in combination at these same concentrations, the bacterial growth inhibition was complete. This demonstrates the highly potent in vitro synergistic activity of CIN when combined with commercial ABXs. This finding could be particularly beneficial in livestock farming, as this sector witnesses the highest quantities of antimicrobial usage, contributing significantly to antimicrobial resistance issues. Further research focused on this natural compound is thus warranted for this reason.
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Affiliation(s)
- Natalia Ferrando
- Facultad de Ciencias de la Salud, Universidad San Jorge, Campus Universitario Villanueva de Gállego, Autovía A-23 Zaragoza-Huesca, km. 510, 50830 Villanueva de Gállego, Spain; (N.F.); (M.R.P.-O.); (D.B.); (G.L.)
| | - María Rosa Pino-Otín
- Facultad de Ciencias de la Salud, Universidad San Jorge, Campus Universitario Villanueva de Gállego, Autovía A-23 Zaragoza-Huesca, km. 510, 50830 Villanueva de Gállego, Spain; (N.F.); (M.R.P.-O.); (D.B.); (G.L.)
| | - Diego Ballestero
- Facultad de Ciencias de la Salud, Universidad San Jorge, Campus Universitario Villanueva de Gállego, Autovía A-23 Zaragoza-Huesca, km. 510, 50830 Villanueva de Gállego, Spain; (N.F.); (M.R.P.-O.); (D.B.); (G.L.)
| | - Guillermo Lorca
- Facultad de Ciencias de la Salud, Universidad San Jorge, Campus Universitario Villanueva de Gállego, Autovía A-23 Zaragoza-Huesca, km. 510, 50830 Villanueva de Gállego, Spain; (N.F.); (M.R.P.-O.); (D.B.); (G.L.)
| | - Eva María Terrado
- Departamento de Didácticas Específicas, Facultad de Educación, Universisad de Zaragoza, Calle Pedro Cerbuna 12, 50009 Zaragoza, Spain;
| | - Elisa Langa
- Facultad de Ciencias de la Salud, Universidad San Jorge, Campus Universitario Villanueva de Gállego, Autovía A-23 Zaragoza-Huesca, km. 510, 50830 Villanueva de Gállego, Spain; (N.F.); (M.R.P.-O.); (D.B.); (G.L.)
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Chubiz LM. The Mar, Sox, and Rob Systems. EcoSal Plus 2023; 11:eesp00102022. [PMID: 37220096 PMCID: PMC10729928 DOI: 10.1128/ecosalplus.esp-0010-2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 03/03/2023] [Indexed: 01/28/2024]
Abstract
Environments inhabited by Enterobacteriaceae are diverse and often stressful. This is particularly true for Escherichia coli and Salmonella during host association in the gastrointestinal systems of animals. There, E. coli and Salmonella must survive exposure to various antimicrobial compounds produced or ingested by their host. A myriad of changes to cellular physiology and metabolism are required to achieve this feat. A central regulatory network responsible for sensing and responding to intracellular chemical stressors like antibiotics are the Mar, Sox, and Rob systems found throughout the Enterobacteriaceae. Each of these distinct regulatory networks controls expression of an overlapping set of downstream genes whose collective effects result in increased resistance to a wide array of antimicrobial compounds. This collection of genes is known as the mar-sox-rob regulon. This review will provide an overview of the mar-sox-rob regulon and molecular architecture of the Mar, Sox, and Rob systems.
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Affiliation(s)
- Lon M. Chubiz
- Department of Biology, University of Missouri–St. Louis, St. Louis, Missouri, USA
- Biochemistry and Biotechnology Program, University of Missouri–St. Louis, St. Louis, Missouri, USA
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Wang J, Wan X, Meng H, Olsen RH, Chen X, Li L. Efflux Pumps and Different Genetic Contexts of tet(X4) Contribute to High Tigecycline Resistance in Escherichia fergusonii from Pigs. Int J Mol Sci 2023; 24:ijms24086923. [PMID: 37108087 PMCID: PMC10138661 DOI: 10.3390/ijms24086923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 03/30/2023] [Accepted: 04/06/2023] [Indexed: 04/29/2023] Open
Abstract
Tigecycline is a last-resort antibiotic for the treatment of infections caused by multidrug-resistant bacteria. The emergence of plasmid-mediated tigecycline resistance genes is posing a serious threat to food safety and human health and has attracted worldwide attention. In this study, we characterized six tigecycline-resistant Escherichia fergusonii strains from porcine nasal swab samples collected from 50 swine farms in China. All the E. fergusonii isolates were highly resistant to tigecycline with minimal inhibitory concentration (MIC) values of 16-32 mg/L, and all contained the tet(X4) gene. In addition, 13-19 multiple resistance genes were identified in these isolates, revealed by whole-genome sequencing analysis. The tet(X4) gene was identified as being located in two different genetic structures, hp-abh-tet(X4)-ISCR2 in five isolates and hp-abh-tet(X4)-ΔISCR2-ISEc57-IS26 in one isolate. The role of efflux pumps in tigecycline resistance was evaluated by using inhibitor carbonyl cyanide 3-chlorophenylhydrazone (CCCP). The MIC values of tigecycline showed a 2- to 4-fold reduction in the presence of CCCP, indicating the involvement of active efflux pumps in tigecycline resistance in E. fergusonii. The tet(X4) gene was found to be transferable to Escherichia coli J53 by conjugation and resulted in the acquisition of tigcycline resistances in the transconjugants. Whole-genome multilocus sequence typing (wgMLST) and phylogenetic analysis showed a close relationship of five isolates originating from different pig farms, suggesting the transmission of tet(X4)-positive E. fergusonii between farms. In conclusion, our findings suggest that E. fergusonii strains in pigs are reservoirs of a transferable tet(X4) gene and provide insights into the tigecycline resistance mechanism as well as the diversity and complexity of the genetic context of tet(X4) in E. fergusonii.
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Affiliation(s)
- Junlin Wang
- Institute of Food Safety and Nutrition, Jinan University, Guangzhou 510632, China
| | - Xiulin Wan
- Institute of Food Safety and Nutrition, Jinan University, Guangzhou 510632, China
| | - Hecheng Meng
- School of Food Science and Engineering, South China University of Technology, Guangzhou 510640, China
| | - Rikke Heidemann Olsen
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 2820 Frederiksberg, Denmark
| | - Xun Chen
- Institute of Food Safety and Nutrition, Jinan University, Guangzhou 510632, China
| | - Lili Li
- Institute of Food Safety and Nutrition, Jinan University, Guangzhou 510632, China
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Co-Lateral Effect of Octenidine, Chlorhexidine and Colistin Selective Pressures on Four Enterobacterial Species: A Comparative Genomic Analysis. Antibiotics (Basel) 2021; 11:antibiotics11010050. [PMID: 35052927 PMCID: PMC8772718 DOI: 10.3390/antibiotics11010050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 12/22/2021] [Accepted: 12/28/2021] [Indexed: 11/17/2022] Open
Abstract
Bacterial adaptation to antiseptic selective pressure might be associated with decreased susceptibility to antibiotics. In Gram-negative bacteria, some correlations between reduced susceptibility to chlorhexidine (CHX) and polymyxins have been recently evidenced in Klebsiella pneumoniae. In the present study, four isolates belonging to distinct enterobacterial species, namely K. pneumoniae, Escherichia coli, Klebsiella oxytoca and Enterobacter cloacae, were submitted to in-vitro selective adaptation to two antiseptics, namely CHX and octenidine (OCT), and to the antibiotic colistin (COL). Using COL as selective agent, mutants showing high MICs for that molecule were recovered for E. cloacae, K. pneumoniae and K. oxytoca, exhibiting a moderate decreased susceptibility to CHX, whereas OCT susceptibility remained unchanged. Using CHX as selective agent, mutants with high MICs for that molecule were recovered for all four species, with a cross-resistance observed for COL, while OCT susceptibility remained unaffected. Finally, selection of mutants using OCT as selective molecule allowed recovery of K. pneumoniae, K. oxytoca and E. cloacae strains showing only slightly increased MICs for that molecule, without any cross-elevated MICs for the two other molecules tested. No E. coli mutant with reduced susceptibility to OCT could be obtained. It was therefore demonstrated that in-vitro mutants with decreased susceptibility to CHX and COL may be selected in E. coli, K. pneumoniae, K. oxytoca and E. cloacae, showing cross-decreased susceptibility to COL and CHX, but no significant impact on OCT efficacy. On the other hand, mutants were difficult to obtain with OCT, being obtained for K. pneumoniae and E. cloacae only, showing only very limited decreased susceptibility in those cases, and with no cross effect on other molecules. Whole genome sequencing enabled deciphering of the molecular basis of adaptation of these isolates under the respective selective pressures, with efflux pumps or lipopolysaccharide biosynthesis being the main mechanisms of adaptation.
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RamAp, an efflux pump regulator carried by an IncHI2 plasmid. Antimicrob Agents Chemother 2021; 66:e0115221. [PMID: 34694885 DOI: 10.1128/aac.01152-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
In investigating the epidemiological trends of Salmonella enterica serovar Goldcoast, we have previously identified several closely related strains with different MICs to azithromycin and quinolones. Genome sequencing and comparison of two very similar MDR strains, R18.0877 and R18.1656, has led to the identification of an extra plasmid-borne ramA gene, ramAp, on the large IncHI2 plasmid carried by R18.0877. The ramAp is located in a 953-bp region on the plasmid, which is identical to that of the Klebsiella quasipneumoniae chromosomal ramA loci. A truncated ISEcp1 located at the adjacent upstream of the putative regulatory region of the ramAp may likely contribute to its mobilization and expression. Introducing the ramAp and the truncated ISEcp1 into E. coli have resulted in elevated expression of efflux pump genes and elevated MICs to chloramphenicol, azithromycin, nalidixic acid, ciprofloxacin, sulfamethoxazole, trimethoprim, tetracycline, and tigecycline. The ramAp is an extra efflux pump activator gene that potentially could be transmitted with the IncHI2 plasmid among bacteria. It is plausible that, with high interspecific conservation, the plasmid-encoded regulator reduces drug susceptibility by activating existing efflux pump systems of the host and thus can be regarded as a new type of auxiliary antimicrobial resistance determinant. Sequences of similar plasmids were found worldwide. Its impact on the emergence of antimicrobial resistance among bacterial pathogens is worrisome.
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Hai D, Huang X. Protective effect of Lactobacillus reuteri Lb11 from chicken intestinal tract against Salmonella Enteritidis SE05 in vitro. Antonie van Leeuwenhoek 2021; 114:1745-1757. [PMID: 34529163 DOI: 10.1007/s10482-021-01625-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 07/19/2021] [Indexed: 02/05/2023]
Abstract
Salmonella infections in eggs with increasing morbidity and mortality exhibit worldwide prevalence. The present study intends to evaluate the efficacy of Lactobacillus reuteri Lb11 (L. reuteri Lb11, isolated from chicken intestinal tract) in inhibiting the growth of multi-drug resistant (MDR) Salmonella Enteritidis SE05 (obtained from egg content). The cell-free cell lysates (CFCL) of L. reuteri Lb11 obtained by the agar spot test performed well on inhibition of the MDR (Multi-Drug Resistant) Salmonella Enteritidis SE05, The heat-inactivated (HI) fraction of L. reuteri Lb11 showed no inhibition activity. By co-culturing with L. reuteri Lb11 in vitro, the growth of S. Enteritidis SE05 decreased along with time, while, the pH value decreased significantly. Furthermore, In order to evaluate the mechanism of action of CFCL of L.reuteri Lb11, the genes related to the transcription level of AcrAB-TolC efflux pump, outer membrane protein OMPs genes and drug resistance genes have been quantified by real-time PCR, when the S. Enteritidis was SE05 exposed to the CFCL of L. reuteri Lb11 (1 × 1012 CFU/mL). Almost all of the AcrAB-TolC efflux pump genes, outer membrane protein genes and antibiotic resistance genes were down-regulated. Especially, the level of ramA, tetA and tetB genes were down-regulated -20.77, -15.85 and -12.42 folds, respectively. L. reuteri Lb11 can effectively prevent the formation of efflux pump to inhibit the production of multidrug-resistant Salmonella Enteritidis in eggs.
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Affiliation(s)
- Dan Hai
- College of Food Science and Technology, Henan Agricultural University, Zhengzhou, 450000, Henan, China
| | - Xianqing Huang
- College of Food Science and Technology, Henan Agricultural University, Zhengzhou, 450000, Henan, China.
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Majewski P, Gutowska A, Sacha P, Schneiders T, Talalaj M, Majewska P, Zebrowska A, Ojdana D, Wieczorek P, Hauschild T, Kowalczuk O, Niklinski J, Radziwon P, Tryniszewska E. Expression of AraC/XylS stress response regulators in two distinct carbapenem-resistant Enterobacter cloacae ST89 biotypes. J Antimicrob Chemother 2021; 75:1146-1150. [PMID: 31960042 DOI: 10.1093/jac/dkz569] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 12/09/2019] [Accepted: 12/20/2019] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND The growing incidence of MDR Gram-negative bacteria is a rapidly emerging challenge in modern medicine. OBJECTIVES We sought to establish the role of intrinsic drug-resistance regulators in combination with specific genetic mutations in 11 Enterobacter cloacae isolates obtained from a single patient within a 7 week period. METHODS The molecular characterization of eight carbapenem-resistant and three carbapenem-susceptible E. cloacae ST89 isolates included expression-level analysis and WGS. Quantitative PCR included: (i) chromosomal cephalosporinase gene (ampC); (ii) membrane permeability factor genes, e.g. ompF, ompC, acrA, acrB and tolC; and (iii) intrinsic regulatory genes, e.g. ramA, ampR, rob, marA and soxS, which confer reductions in antibiotic susceptibility. RESULTS In this study we describe the influence of the alterations in membrane permeability (ompF and ompC levels), intrinsic regulatory genes (ramA, marA, soxS) and intrinsic chromosomal cephalosporinase AmpC on reductions in carbapenem susceptibility of E. cloacae clinical isolates. Interestingly, only the first isolate possessed the acquired VIM-4 carbapenemase, which has been lost in subsequent isolates. The remaining XDR E. cloacae ST89 isolates presented complex carbapenem-resistance pathways, which included perturbations in permeability of bacterial membranes mediated by overexpression of ramA, encoding an AraC/XylS global regulator. Moreover, susceptible isolates differed significantly from other isolates in terms of marA down-regulation and soxS up-regulation. CONCLUSIONS Molecular mechanisms of resistance among carbapenem-resistant E. cloacae included production of acquired VIM-4 carbapenemase, significant alterations in membrane permeability due to increased expression of ramA, encoding an AraC/XylS global regulator, and the overproduction of chromosomal AmpC cephalosporinase.
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Affiliation(s)
- Piotr Majewski
- Department of Microbiological Diagnostics and Infectious Immunology, Medical University of Bialystok, Bialystok, Poland
| | - Anna Gutowska
- Department of Microbiological Diagnostics and Infectious Immunology, Medical University of Bialystok, Bialystok, Poland
| | - Pawel Sacha
- Department of Microbiological Diagnostics and Infectious Immunology, Medical University of Bialystok, Bialystok, Poland
| | | | - Mariola Talalaj
- Department of Anaesthesiology and Intensive Care with Postoperative Unit, University Children's Clinical Hospital, Bialystok, Poland
| | | | | | - Dominika Ojdana
- Department of Microbiological Diagnostics and Infectious Immunology, Medical University of Bialystok, Bialystok, Poland
| | - Piotr Wieczorek
- Department of Microbiological Diagnostics and Infectious Immunology, Medical University of Bialystok, Bialystok, Poland
| | - Tomasz Hauschild
- Department of Microbiology, Institute of Biology, University of Bialystok, Bialystok, Poland
| | - Oksana Kowalczuk
- Department of Clinical Molecular Biology, Medical University of Bialystok, Bialystok, Poland
| | - Jacek Niklinski
- Department of Clinical Molecular Biology, Medical University of Bialystok, Bialystok, Poland
| | - Piotr Radziwon
- Regional Centre for Transfusion Medicine, Bialystok, Poland.,Department of Hematology, Medical University of Bialystok, Bialystok, Poland
| | - Elzbieta Tryniszewska
- Department of Microbiological Diagnostics and Infectious Immunology, Medical University of Bialystok, Bialystok, Poland
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Serratia marcescens RamA Expression Is under PhoP-Dependent Control and Modulates Lipid A-Related Gene Transcription and Antibiotic Resistance Phenotypes. J Bacteriol 2021; 203:e0052320. [PMID: 33927048 DOI: 10.1128/jb.00523-20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Serratia marcescens is an enteric bacterium that can function as an opportunistic pathogen with increasing incidence in clinical settings. This is mainly due to the ability to express a wide range of virulence factors and the acquisition of antibiotic resistance mechanisms. For these reasons, S. marcescens has been declared by the World Health Organization (WHO) as a research priority to develop alternative antimicrobial strategies. In this study, we found a PhoP-binding motif in the promoter region of transcriptional regulator RamA of S. marcescens RM66262. We demonstrated that the expression of ramA is autoregulated and that ramA is also part of the PhoP/PhoQ regulon. We have also shown that PhoP binds directly and specifically to ramA, mgtE1, mgtE2, lpxO1, and lpxO2 promoter regions and that RamA binds to ramA and lpxO1 but not to mgtE1 and lpxO2, suggesting an indirect control for the latter genes. Finally, we have demonstrated that in S. marcescens, RamA overexpression induces the AcrAB-TolC efflux pump, required to reduce the susceptibility of the bacteria to tetracycline and nalidixic acid. In sum, we here provide the first report describing the regulation of ramA under the control of the PhoP/PhoQ regulon and the regulatory role of RamA in S. marcescens. IMPORTANCE We demonstrate that in S. marcescens, the transcriptional regulator RamA is autoregulated and also controlled by the PhoP/PhoQ signal transduction system. We show that PhoP is able to directly and specifically bind to ramA, mgtE1, mgtE2, lpxO1, and lpxO2 promoter regions. In addition, RamA is able to directly interact with the promoter regions of ramA and lpxO1 but indirectly regulates mgtE1 and lpxO2. Finally, we found that in S. marcescens, RamA overexpression induces the AcrAB-TolC efflux pump, required to reduce susceptibility to tetracycline and nalidixic acid. Collectively, these results further our understanding of the PhoP/PhoQ regulon in S. marcescens and demonstrate the involvement of RamA in the protection against antibiotic challenges.
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Yaghoubi S, Zekiy AO, Krutova M, Gholami M, Kouhsari E, Sholeh M, Ghafouri Z, Maleki F. Tigecycline antibacterial activity, clinical effectiveness, and mechanisms and epidemiology of resistance: narrative review. Eur J Clin Microbiol Infect Dis 2021; 41:1003-1022. [PMID: 33403565 PMCID: PMC7785128 DOI: 10.1007/s10096-020-04121-1] [Citation(s) in RCA: 79] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 12/02/2020] [Indexed: 12/14/2022]
Abstract
Tigecycline is unique glycylcycline class of semisynthetic antimicrobial agents developed for the treatment of polymicrobial infections caused by multidrug-resistant Gram-positive and Gram-negative pathogens. Tigecycline evades the main tetracycline resistance genetic mechanisms, such as tetracycline-specific efflux pump acquisition and ribosomal protection, via the addition of a glycyclamide moiety to the 9-position of minocycline. The use of the parenteral form of tigecycline is approved for complicated skin and skin structure infections (excluding diabetes foot infection), complicated intra-abdominal infections, and community-acquired bacterial pneumonia in adults. New evidence also suggests the effectiveness of tigecycline for the treatment of severe Clostridioides difficile infections. Tigecycline showed in vitro susceptibility to Coxiella spp., Rickettsia spp., and multidrug-resistant Neisseria gonnorrhoeae strains which indicate the possible use of tigecycline in the treatment of infections caused by these pathogens. Except for intrinsic, or often reported resistance in some Gram-negatives, tigecycline is effective against a wide range of multidrug-resistant nosocomial pathogens. Herein, we summarize the currently available data on tigecycline pharmacokinetics and pharmacodynamics, its mechanism of action, the epidemiology of tigecycline resistance, and its clinical effectiveness.
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Affiliation(s)
- Sajad Yaghoubi
- Department of Clinical Microbiology, Iranshahr University of Medical Sciences, Iranshahr, Iran
| | - Angelina Olegovna Zekiy
- Department of Prosthetic Dentistry, Sechenov First Moscow State Medical University, Russian Federation, Trubetskaya st., 8-2, 119991, Moscow, Russia
| | - Marcela Krutova
- Department of Medical Microbiology, 2nd Faculty of Medicine, Charles University and Motol University Hospital, Prague, Czech Republic
| | - Mehrdad Gholami
- Department of Microbiology and Virology, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Iran
| | - Ebrahim Kouhsari
- Laboratory Sciences Research Center, Golestan University of Medical Sciences, P.O. Box 6939177143, Gorgan- Sari Road, Golestan Province, Gorgan, Iran. .,Department of Laboratory Sciences, Faculty of Paramedicine, Golestan University of Medical Sciences, P.O. Box 6939177143, Gorgan- Sari Road, Golestan Province, Gorgan, Iran.
| | - Mohammad Sholeh
- Department of Microbiology, Faculty of Medicine, Iran University of Medical Sciences, Tehran, Iran
| | - Zahra Ghafouri
- Department of Biochemistry, Biophysics and Genetics, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Iran
| | - Farajolah Maleki
- Department of Laboratory Sciences, School of Allied Medical Sciences, Ilam University of Medical sciences, Ilam, Iran.
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12
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ramR Deletion in an Enterobacter hormaechei Isolate as a Consequence of Therapeutic Failure of Key Antibiotics in a Long-Term Hospitalized Patient. Antimicrob Agents Chemother 2020; 64:AAC.00962-20. [PMID: 32778545 DOI: 10.1128/aac.00962-20] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Accepted: 07/22/2020] [Indexed: 11/20/2022] Open
Abstract
Genome changes are central to the adaptation of bacteria, especially under antibiotic pressure. The aim of this study was to report phenotypic and genomic adaptations undergone by an Enterobacter hormaechei clinical strain that became highly resistant to key antimicrobials during a 4-month period in a patient hospitalized in an intensive care unit (ICU). All six clinical E. hormaechei strains isolated in one ICU-hospitalized patient have been studied. MICs regarding 17 antimicrobial molecules have been measured. Single nucleotide polymorphisms (SNPs) were determined on the sequenced genomes. The expression of genes involved in antibiotic resistance among Enterobacter cloacae complex strains were determined by reverse transcription-quantitative PCR (qRT-PCR). All the strains belonged to sequence type 66 and were distant by a maximum of nine SNPs. After 3 months of hospitalization, three strains presented a significant increase in MICs for ceftazidime, cefepime, temocillin, ertapenem, tigecycline, ciprofloxacin, and chloramphenicol. Those resistant strains did not acquire additional antibiotic resistance genes but harbored a 16-bp deletion in the ramR gene. This deletion led to upregulated expression of RamA, AcrA, AcrB, and TolC and downregulated expression of OmpF. The ΔramR mutant harbored the same phenotype as the resistant clinical strains regarding tigecycline, chloramphenicol, and ciprofloxacin. The increased expression of RamA due to partial deletion in the ramR gene led to a cross-resistance phenotype by an increase of antibiotic efflux through the AcrAB-TolC pump and a decrease of antibiotic permeability by porin OmpF. ramR appears to be an important adaptative trait for E. hormaechei strains.
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13
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Hennessen F, Miethke M, Zaburannyi N, Loose M, Lukežič T, Bernecker S, Hüttel S, Jansen R, Schmiedel J, Fritzenwanker M, Imirzalioglu C, Vogel J, Westermann AJ, Hesterkamp T, Stadler M, Wagenlehner F, Petković H, Herrmann J, Müller R. Amidochelocardin Overcomes Resistance Mechanisms Exerted on Tetracyclines and Natural Chelocardin. Antibiotics (Basel) 2020; 9:antibiotics9090619. [PMID: 32962088 PMCID: PMC7559539 DOI: 10.3390/antibiotics9090619] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Revised: 09/16/2020] [Accepted: 09/17/2020] [Indexed: 12/21/2022] Open
Abstract
The reassessment of known but neglected natural compounds is a vital strategy for providing novel lead structures urgently needed to overcome antimicrobial resistance. Scaffolds with resistance-breaking properties represent the most promising candidates for a successful translation into future therapeutics. Our study focuses on chelocardin, a member of the atypical tetracyclines, and its bioengineered derivative amidochelocardin, both showing broad-spectrum antibacterial activity within the ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) panel. Further lead development of chelocardins requires extensive biological and chemical profiling to achieve favorable pharmaceutical properties and efficacy. This study shows that both molecules possess resistance-breaking properties enabling the escape from most common tetracycline resistance mechanisms. Further, we show that these compounds are potent candidates for treatment of urinary tract infections due to their in vitro activity against a large panel of multidrug-resistant uropathogenic clinical isolates. In addition, the mechanism of resistance to natural chelocardin was identified as relying on efflux processes, both in the chelocardin producer Amycolatopsis sulphurea and in the pathogen Klebsiella pneumoniae. Resistance development in Klebsiella led primarily to mutations in ramR, causing increased expression of the acrAB-tolC efflux pump. Most importantly, amidochelocardin overcomes this resistance mechanism, revealing not only the improved activity profile but also superior resistance-breaking properties of this novel antibacterial compound.
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Affiliation(s)
- Fabienne Hennessen
- Department of Microbial Natural Products, Helmholtz Institute for Pharmaceutical Research Saarland (HIPS)—Helmholtz Centre for Infection Research (HZI), and Department of Pharmacy, Saarland University Campus E8.1, 66123 Saarbrücken, Germany; (F.H.); (M.M.); (N.Z.); (T.L.)
- German Center for Infection Research (DZIF), Partner Site Hannover-Braunschweig, 38124 Braunschweig, Germany; (S.B.); (S.H.); (R.J.); (T.H.); (M.S.)
| | - Marcus Miethke
- Department of Microbial Natural Products, Helmholtz Institute for Pharmaceutical Research Saarland (HIPS)—Helmholtz Centre for Infection Research (HZI), and Department of Pharmacy, Saarland University Campus E8.1, 66123 Saarbrücken, Germany; (F.H.); (M.M.); (N.Z.); (T.L.)
- German Center for Infection Research (DZIF), Partner Site Hannover-Braunschweig, 38124 Braunschweig, Germany; (S.B.); (S.H.); (R.J.); (T.H.); (M.S.)
| | - Nestor Zaburannyi
- Department of Microbial Natural Products, Helmholtz Institute for Pharmaceutical Research Saarland (HIPS)—Helmholtz Centre for Infection Research (HZI), and Department of Pharmacy, Saarland University Campus E8.1, 66123 Saarbrücken, Germany; (F.H.); (M.M.); (N.Z.); (T.L.)
- German Center for Infection Research (DZIF), Partner Site Hannover-Braunschweig, 38124 Braunschweig, Germany; (S.B.); (S.H.); (R.J.); (T.H.); (M.S.)
| | - Maria Loose
- Clinic for Urology, Paediatric Urology & Andrology, Justus-Liebig University Gießen, and German Center for Infection Research (DZIF), Partner Site Giessen-Marburg-Langen, 35392 Gießen, Germany; (M.L.); (F.W.)
| | - Tadeja Lukežič
- Department of Microbial Natural Products, Helmholtz Institute for Pharmaceutical Research Saarland (HIPS)—Helmholtz Centre for Infection Research (HZI), and Department of Pharmacy, Saarland University Campus E8.1, 66123 Saarbrücken, Germany; (F.H.); (M.M.); (N.Z.); (T.L.)
- German Center for Infection Research (DZIF), Partner Site Hannover-Braunschweig, 38124 Braunschweig, Germany; (S.B.); (S.H.); (R.J.); (T.H.); (M.S.)
- National Institute of Biology, Večna pot 111, 1000 Ljubljana, Slovenia
| | - Steffen Bernecker
- German Center for Infection Research (DZIF), Partner Site Hannover-Braunschweig, 38124 Braunschweig, Germany; (S.B.); (S.H.); (R.J.); (T.H.); (M.S.)
- Department of Microbial Drugs, Helmholtz Centre for Infection Research (HZI), Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Stephan Hüttel
- German Center for Infection Research (DZIF), Partner Site Hannover-Braunschweig, 38124 Braunschweig, Germany; (S.B.); (S.H.); (R.J.); (T.H.); (M.S.)
- Department of Microbial Drugs, Helmholtz Centre for Infection Research (HZI), Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Rolf Jansen
- German Center for Infection Research (DZIF), Partner Site Hannover-Braunschweig, 38124 Braunschweig, Germany; (S.B.); (S.H.); (R.J.); (T.H.); (M.S.)
- Department of Microbial Drugs, Helmholtz Centre for Infection Research (HZI), Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Judith Schmiedel
- Institute of Medical Microbiology, Justus-Liebig University Gießen, and German Center for Infection Research (DZIF), Partner Site Giessen-Marburg-Langen, 35390 Gießen, Germany; (J.S.); (M.F.); (C.I.)
| | - Moritz Fritzenwanker
- Institute of Medical Microbiology, Justus-Liebig University Gießen, and German Center for Infection Research (DZIF), Partner Site Giessen-Marburg-Langen, 35390 Gießen, Germany; (J.S.); (M.F.); (C.I.)
| | - Can Imirzalioglu
- Institute of Medical Microbiology, Justus-Liebig University Gießen, and German Center for Infection Research (DZIF), Partner Site Giessen-Marburg-Langen, 35390 Gießen, Germany; (J.S.); (M.F.); (C.I.)
| | - Jörg Vogel
- Helmholtz Institute for RNA-based Infection Research (HIRI), Helmholtz Centre for Infection Research (HZI) and Institute of Molecular Infection Biology (IMIB), University of Würzburg, Josef-Schneider-Str. 2, 97080 Würzburg, Germany; (J.V.); (A.J.W.)
| | - Alexander J. Westermann
- Helmholtz Institute for RNA-based Infection Research (HIRI), Helmholtz Centre for Infection Research (HZI) and Institute of Molecular Infection Biology (IMIB), University of Würzburg, Josef-Schneider-Str. 2, 97080 Würzburg, Germany; (J.V.); (A.J.W.)
| | - Thomas Hesterkamp
- German Center for Infection Research (DZIF), Partner Site Hannover-Braunschweig, 38124 Braunschweig, Germany; (S.B.); (S.H.); (R.J.); (T.H.); (M.S.)
| | - Marc Stadler
- German Center for Infection Research (DZIF), Partner Site Hannover-Braunschweig, 38124 Braunschweig, Germany; (S.B.); (S.H.); (R.J.); (T.H.); (M.S.)
- Department of Microbial Drugs, Helmholtz Centre for Infection Research (HZI), Inhoffenstrasse 7, 38124 Braunschweig, Germany
| | - Florian Wagenlehner
- Clinic for Urology, Paediatric Urology & Andrology, Justus-Liebig University Gießen, and German Center for Infection Research (DZIF), Partner Site Giessen-Marburg-Langen, 35392 Gießen, Germany; (M.L.); (F.W.)
| | - Hrvoje Petković
- Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia;
| | - Jennifer Herrmann
- Department of Microbial Natural Products, Helmholtz Institute for Pharmaceutical Research Saarland (HIPS)—Helmholtz Centre for Infection Research (HZI), and Department of Pharmacy, Saarland University Campus E8.1, 66123 Saarbrücken, Germany; (F.H.); (M.M.); (N.Z.); (T.L.)
- German Center for Infection Research (DZIF), Partner Site Hannover-Braunschweig, 38124 Braunschweig, Germany; (S.B.); (S.H.); (R.J.); (T.H.); (M.S.)
- Correspondence: (J.H.); (R.M.); Tel.: +49-681-98806-3101 (J.H.); +49-681-98806-3000 (R.M.)
| | - Rolf Müller
- Department of Microbial Natural Products, Helmholtz Institute for Pharmaceutical Research Saarland (HIPS)—Helmholtz Centre for Infection Research (HZI), and Department of Pharmacy, Saarland University Campus E8.1, 66123 Saarbrücken, Germany; (F.H.); (M.M.); (N.Z.); (T.L.)
- German Center for Infection Research (DZIF), Partner Site Hannover-Braunschweig, 38124 Braunschweig, Germany; (S.B.); (S.H.); (R.J.); (T.H.); (M.S.)
- Correspondence: (J.H.); (R.M.); Tel.: +49-681-98806-3101 (J.H.); +49-681-98806-3000 (R.M.)
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14
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Cheng C, Ying Y, Zhou D, Zhu L, Lu J, Li A, Bao Q, Zhu M. RamA, a transcriptional regulator conferring florfenicol resistance in Leclercia adecarboxylata R25. Folia Microbiol (Praha) 2020; 65:1051-1060. [PMID: 32857336 PMCID: PMC7716942 DOI: 10.1007/s12223-020-00816-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 08/19/2020] [Indexed: 12/11/2022]
Abstract
Due to the inappropriate use of florfenicol in agricultural practice, florfenicol resistance has become increasingly serious. In this work, we studied the novel florfenicol resistance mechanism of an animal-derived Leclercia adecarboxylata strain R25 with high-level florfenicol resistance. A random genomic DNA library was constructed to screen the novel florfenicol resistance gene. Gene cloning, gene knockout, and complementation combined with the minimum inhibitory concentration (MIC) detection were conducted to determine the function of the resistance-related gene. Sequencing and bioinformatics methods were applied to analyze the structure of the resistance gene-related sequences. Finally, we obtained a regulatory gene of an RND (resistance-nodulation-cell division) system, ramA, that confers resistance to florfenicol and other antibiotics. The ramA-deleted variant (LA-R25ΔramA) decreased the level of resistance against florfenicol and several other antibiotics, while a ramA-complemented strain (pUCP24-prom-ramA/LA-R25ΔramA) restored the drug resistance. The whole-genome sequencing revealed that there were five RND efflux pump genes (mdtABC, acrAB, acrD, acrEF, and acrAB-like) encoded over the chromosome, and ramA located upstream of the acrAB-like genes. The results of this work suggest that ramA confers resistance to florfenicol and other structurally unrelated antibiotics, presumably by regulating the RND efflux pump genes in L. adecarboxylata R25.
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Affiliation(s)
- Cong Cheng
- Vocational and Technical College, Lishui University, Lishui, 323000, China
| | - Yuanyuan Ying
- Medical Research Center, Taizhou Hospital of Zhejiang Province, Taizhou, 317000, Zhejiang, China
| | - Danying Zhou
- School of Laboratory Medicine and Life Sciences/Institute of Biomedical Informatics, Wenzhou Medical University, Wenzhou, 325035, Zhejiang, China
| | - Licheng Zhu
- Vocational and Technical College, Lishui University, Lishui, 323000, China
| | - Junwan Lu
- Medical Research Center, Taizhou Hospital of Zhejiang Province, Taizhou, 317000, Zhejiang, China
| | - Aifang Li
- The Fifth Affiliated Hospital, Wenzhou Medical University, Lishui, 323000, Zhejiang, China
| | - Qiyu Bao
- Medical Research Center, Taizhou Hospital of Zhejiang Province, Taizhou, 317000, Zhejiang, China
| | - Mei Zhu
- Department of Clinical Laboratory, Zhejiang Hospital, Hangzhou, 310013, Zhejiang, China.
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15
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Ferrand A, Vergalli J, Pagès JM, Davin-Regli A. An Intertwined Network of Regulation Controls Membrane Permeability Including Drug Influx and Efflux in Enterobacteriaceae. Microorganisms 2020; 8:E833. [PMID: 32492979 PMCID: PMC7355843 DOI: 10.3390/microorganisms8060833] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 05/29/2020] [Accepted: 05/31/2020] [Indexed: 12/19/2022] Open
Abstract
The transport of small molecules across membranes is a pivotal step for controlling the drug concentration into the bacterial cell and it efficiently contributes to the antibiotic susceptibility in Enterobacteriaceae. Two types of membrane transports, passive and active, usually represented by porins and efflux pumps, are involved in this process. Importantly, the expression of these transporters and channels are modulated by an armamentarium of tangled regulatory systems. Among them, Helix-turn-Helix (HTH) family regulators (including the AraC/XylS family) and the two-component systems (TCS) play a key role in bacterial adaptation to environmental stresses and can manage a decrease of porin expression associated with an increase of efflux transporters expression. In the present review, we highlight some recent genetic and functional studies that have substantially contributed to our better understanding of the sophisticated mechanisms controlling the transport of small solutes (antibiotics) across the membrane of Enterobacteriaceae. This information is discussed, taking into account the worrying context of clinical antibiotic resistance and fitness of bacterial pathogens. The localization and relevance of mutations identified in the respective regulation cascades in clinical resistant strains are discussed. The possible way to bypass the membrane/transport barriers is described in the perspective of developing new therapeutic targets to combat bacterial resistance.
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Affiliation(s)
| | | | | | - Anne Davin-Regli
- UMR_MD1, U-1261, Aix-Marseille University, INSERM, SSA, IRBA, MCT, Faculté de Pharmacie, 27 Bd Jean Moulin, 13385 Marseille CEDEX 05, France; (A.F.); (J.V.); (J.-M.P.)
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16
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Nascimento RJ, Frasão BS, Dias TS, Nascimento ER, Tavares LS, Almeida VL, Aquino MHC. Detection of efflux pump CmeABC in enrofloxacin resistant Campylobacter spp. strains isolated from broiler chickens (Gallus gallus domesticus) in the state of Rio de Janeiro, Brazil. PESQUISA VETERINÁRIA BRASILEIRA 2019. [DOI: 10.1590/1678-5150-pvb-6004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
ABSTRACT: Fowls are the main reservoirs of the highly important food-originating pathogen called Campylobacter spp. and broilers’ meat and byproducts are the main vehicles of this microorganism. Increasing of Campylobacter spp. resistant strains to fluorquinolones, an antimicrobial class often employed in poultry farming and in human medicine has become a great concern to poultry breeders. In fact, several studies evaluated increasing bacterial resistance against these antimicrobial agents. The role of CmeABC efflux system has been underscored among the resistance mechanisms in Campylobacter spp. to fluorquinolones. This study investigated the occurrence of CmeABC efflux pump in 81 and 78 enrofloxacin resistant strains of Campylobacter jejuni and C. coli respectively, isolated from broilers collected from six abattoirs situated at São José do Vale do Rio Preto/RJ poultry center and from two commercial abattoirs situated at Metropolitan Region of Rio de Janeiro, from 2013 to 2016. The resistance to enrofloxacin was assessed by agar dilution to determine minimum inhibitory concentration (MIC). The CmeABC efflux system was investigated through the detection of genes genes cmeA, cmeB and cmeC by PCR. The activity of CmeABC efflux pump was investigated in 20 strains by using the efflux pump inhibitor Phenylalanine-Arginine β-Naphthylamide (PAβN). The three genes cmeA, cmeB and cmeC were detected in 94.3% of the strains (C. jejuni = 80 and C. coli = 70), whereas the system was absent or incomplete in 5.7% of strains (C. jejuni = 1 and C. coli = 8). MIC varied between 0.5μg/ml and 64μg/ml, and 88.7% of strains were enrofloxacin resistant and 11.3% featuring intermediate resistance. The inhibition of the efflux pump by PAβN reduced the MIC to enrofloxacin up to eight times in fifteen strains (75%). These results indicate that this system is frequent and active in Campylobacter spp. Resistant strains in the presence of enrofloxacin.
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17
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Passarelli-Araujo H, Palmeiro JK, Moharana KC, Pedrosa-Silva F, Dalla-Costa LM, Venancio TM. Genomic analysis unveils important aspects of population structure, virulence, and antimicrobial resistance in Klebsiella aerogenes. FEBS J 2019; 286:3797-3810. [PMID: 31319017 DOI: 10.1111/febs.15005] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 06/03/2019] [Accepted: 07/16/2019] [Indexed: 12/22/2022]
Abstract
Klebsiella aerogenes is an important pathogen in healthcare-associated infections. Nevertheless, in comparison to other clinically important pathogens, K. aerogenes population structure, genetic diversity, and pathogenicity remain poorly understood. Here, we elucidate K. aerogenes clonal complexes (CCs) and genomic features associated with resistance and virulence. We present a detailed description of the population structure of K. aerogenes based on 97 publicly available genomes by using both multilocus sequence typing and single-nucleotide polymorphisms extracted from the core genome. We also assessed virulence and resistance profiles using Virulence Finder Database and Comprehensive Antibiotic Resistance Database, respectively. We show that K. aerogenes has an open pangenome and a large effective population size, which account for its high genomic diversity and support that negative selection prevents fixation of most deleterious alleles. The population is structured in at least 10 CCs, including two novel ones identified here, CC9 and CC10. The repertoires of resistance genes comprise a high number of antibiotic efflux proteins as well as narrow- and extended-spectrum β-lactamases. Regarding the population structure, we identified two clusters based on virulence profiles because of the presence of the toxin-encoding clb operon and the siderophore production genes, irp and ybt. Notably, CC3 comprises the majority of K. aerogenes isolates associated with hospital outbreaks, emphasizing the importance of constant monitoring of this pathogen. Collectively, our results may provide a foundation for the development of new therapeutic and surveillance strategies worldwide.
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Affiliation(s)
- Hemanoel Passarelli-Araujo
- Laboratório de Química e Função de Proteínas e Peptídeos, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brazil.,Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Jussara K Palmeiro
- Laboratório de Microbiologia Clínica, Departamento de Análises Clínicas, Centro de Ciências da Saúde, Universidade Federal de Santa Catarina, Florianópolis, Brazil.,Faculdade Pequeno Príncipe, Instituto de Pesquisa Pelé Pequeno Príncipe, Curitiba, Brazil
| | - Kanhu C Moharana
- Laboratório de Química e Função de Proteínas e Peptídeos, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brazil
| | - Francisnei Pedrosa-Silva
- Laboratório de Química e Função de Proteínas e Peptídeos, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brazil
| | - Libera M Dalla-Costa
- Faculdade Pequeno Príncipe, Instituto de Pesquisa Pelé Pequeno Príncipe, Curitiba, Brazil
| | - Thiago M Venancio
- Laboratório de Química e Função de Proteínas e Peptídeos, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, Brazil
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18
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Enterobacter spp.: Update on Taxonomy, Clinical Aspects, and Emerging Antimicrobial Resistance. Clin Microbiol Rev 2019; 32:32/4/e00002-19. [PMID: 31315895 DOI: 10.1128/cmr.00002-19] [Citation(s) in RCA: 233] [Impact Index Per Article: 46.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The genus Enterobacter is a member of the ESKAPE group, which contains the major resistant bacterial pathogens. First described in 1960, this group member has proven to be more complex as a result of the exponential evolution of phenotypic and genotypic methods. Today, 22 species belong to the Enterobacter genus. These species are described in the environment and have been reported as opportunistic pathogens in plants, animals, and humans. The pathogenicity/virulence of this bacterium remains rather unclear due to the limited amount of work performed to date in this field. In contrast, its resistance against antibacterial agents has been extensively studied. In the face of antibiotic treatment, it is able to manage different mechanisms of resistance via various local and global regulator genes and the modulation of the expression of different proteins, including enzymes (β-lactamases, etc.) or membrane transporters, such as porins and efflux pumps. During various hospital outbreaks, the Enterobacter aerogenes and E. cloacae complex exhibited a multidrug-resistant phenotype, which has stimulated questions about the role of cascade regulation in the emergence of these well-adapted clones.
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19
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Abstract
The transport of small molecules across membranes is essential for the import of nutrients and other energy sources into the cell and, for the export of waste and other potentially harmful byproducts out of the cell. While hydrophobic molecules are permeable to membranes, ions and other small polar molecules require transport via specialized membrane transport proteins . The two major classes of membrane transport proteins are transporters and channels. With our focus here on porins-major class of non-specific diffusion channel proteins , we will highlight some recent structural biology reports and functional assays that have substantially contributed to our understanding of the mechanism that mediates uptake of small molecules, including antibiotics, across the outer membrane of Enterobacteriaceae . We will also review advances in the regulation of porin expression and porin biogenesis and discuss these pathways as new therapeutic targets.
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Affiliation(s)
- Muriel Masi
- UMR_MD1, Inserm U1261, IRBA, Membranes et Cibles Thérapeutiques, Facultés de Médecine et de Pharmacie, Aix-Marseille Université, Marseille, France
| | | | - Jean-Marie Pagès
- UMR_MD1, Inserm U1261, IRBA, Membranes et Cibles Thérapeutiques, Facultés de Médecine et de Pharmacie, Aix-Marseille Université, Marseille, France.
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Jiménez-Castellanos JC, Wan Nur Ismah WAK, Takebayashi Y, Findlay J, Schneiders T, Heesom KJ, Avison MB. Envelope proteome changes driven by RamA overproduction in Klebsiella pneumoniae that enhance acquired β-lactam resistance. J Antimicrob Chemother 2018; 73:88-94. [PMID: 29029194 DOI: 10.1093/jac/dkx345] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 08/25/2017] [Indexed: 12/20/2022] Open
Abstract
Objectives In Klebsiella pneumoniae, overproduction of RamA results in reduced envelope permeability and reduced antimicrobial susceptibility but clinically relevant resistance is rarely observed. Here we have tested whether RamA overproduction can enhance acquired β-lactam resistance mechanisms in K. pneumoniae and have defined the envelope protein abundance changes upon RamA overproduction during growth in low and high osmolarity media. Methods Envelope permeability was estimated using a fluorescent dye accumulation assay. β-Lactam susceptibility was measured using disc testing. Total envelope protein production was quantified using LC-MS/MS proteomics and transcript levels were quantified using real-time RT-PCR. Results RamA overproduction enhanced β-lactamase-mediated β-lactam resistance, in some cases dramatically, without altering β-lactamase production. It increased production of efflux pumps and decreased OmpK35 porin production, though micF overexpression showed that OmpK35 reduction has little impact on envelope permeability. A survey of K. pneumoniae bloodstream isolates revealed ramA hyperexpression in 3 of 4 carbapenemase producers, 1 of 21 CTX-M producers and 2 of 19 strains not carrying CTX-M or carbapenemases. Conclusions Whilst RamA is not a key mediator of antibiotic resistance in K. pneumoniae on its own, it is potentially important for enhancing the spectrum of acquired β-lactamase-mediated β-lactam resistance. LC-MS/MS proteomics analysis has revealed that this enhancement is achieved predominantly through activation of efflux pump production.
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Affiliation(s)
| | - Wan Ahmad Kamil Wan Nur Ismah
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK.,Faculty of Biotechnology & Biomolecular Sciences, Universiti Putra Malaysia, Selangor Darul Ehsan, Malaysia
| | - Yuiko Takebayashi
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
| | - Jacqueline Findlay
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
| | - Thamarai Schneiders
- Division of Infection and Pathway Medicine, University of Edinburgh, Edinburgh, UK
| | - Kate J Heesom
- University of Bristol Proteomics Facility, Bristol, UK
| | - Matthew B Avison
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
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Neuberger A, Du D, Luisi BF. Structure and mechanism of bacterial tripartite efflux pumps. Res Microbiol 2018; 169:401-413. [PMID: 29787834 DOI: 10.1016/j.resmic.2018.05.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2017] [Revised: 02/20/2018] [Accepted: 05/14/2018] [Indexed: 12/22/2022]
Abstract
Efflux pumps are membrane proteins which contribute to multi-drug resistance. In Gram-negative bacteria, some of these pumps form complex tripartite assemblies in association with an outer membrane channel and a periplasmic membrane fusion protein. These tripartite machineries span both membranes and the periplasmic space, and they extrude from the bacterium chemically diverse toxic substrates. In this chapter, we summarise current understanding of the structural architecture, functionality, and regulation of tripartite multi-drug efflux assemblies.
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Affiliation(s)
- Arthur Neuberger
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK
| | - Dijun Du
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK
| | - Ben F Luisi
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, UK.
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Jia X, Dai W, Ma W, Yan J, He J, Li S, Li C, Yang S, Xu X, Sun S, Shi J, Zhang L. Carbapenem-Resistant E. cloacae in Southwest China: Molecular Analysis of Resistance and Risk Factors for Infections Caused by NDM-1-Producers. Front Microbiol 2018; 9:658. [PMID: 29670607 PMCID: PMC5893741 DOI: 10.3389/fmicb.2018.00658] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2017] [Accepted: 03/21/2018] [Indexed: 11/16/2022] Open
Abstract
Carbapenem-resistant Enterobacteriaceae (CRE) has been considered a serious global threat, but carbapenem resistance remains relatively uncommon in E. cloacae, especially in China. The aim of this study was to characterize carbapenem-resistant E. cloacae (CR-ECL) isolates from 2012 to 2016 in Southwest China. Our study revealed that 20 (15.2%) of the 132 CR-ECL isolates obtained from patients were identified as NDM-1, with most isolates carrying the IncFIIA plasmids. Notably, we initially observed that the E. cloacae strain co-harbored NDM-1 and IMP-8 carbapenemases simultaneously. Analysis of the genetic environment of these two genes has revealed that the highly conserved regions (blaNDM-1-bleMBL-trpF-tat) are associated with the dissemination of NDM-1, while IS26, intI1, and tniC could be involved in the spread of IMP-8. Molecular epidemiology studies showed the nosocomial outbreak caused by NDM-1-producing E. cloacae ST88. Transferring from another hospital and previous carbapenem exposure were identified as independent risk factors for the acquisition of NDM-1-producing E. cloacae. These findings emphasize the need for intensive surveillance and precautions to monitor the further spread of NDM-1 in China.
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Affiliation(s)
- Xiaojiong Jia
- Department of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Wei Dai
- Department of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Weijia Ma
- Department of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Jinrong Yan
- Department of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Jianchun He
- Department of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Shuang Li
- Department of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Congya Li
- Department of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Shuangshuang Yang
- Department of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Xiuyu Xu
- Department of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Shan Sun
- Department of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Jing Shi
- Department of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Liping Zhang
- Department of Laboratory Medicine, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
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Dam S, Pagès JM, Masi M. Stress responses, outer membrane permeability control and antimicrobial resistance in Enterobacteriaceae. MICROBIOLOGY-SGM 2018; 164:260-267. [PMID: 29458656 DOI: 10.1099/mic.0.000613] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Bacteria have evolved several strategies to survive a myriad of harmful conditions in the environment and in hosts. In Gram-negative bacteria, responses to nutrient limitation, oxidative or nitrosative stress, envelope stress, exposure to antimicrobials and other growth-limiting stresses have been linked to the development of antimicrobial resistance. This results from the activation of protective changes to cell physiology (decreased outer membrane permeability), resistance transporters (drug efflux pumps), resistant lifestyles (biofilms, persistence) and/or resistance mutations (target mutations, production of antibiotic modification/degradation enzymes). In targeting and interfering with essential physiological mechanisms, antimicrobials themselves are considered as stresses to which protective responses have also evolved. In this review, we focus on envelope stress responses that affect the expression of outer membrane porins and their impact on antimicrobial resistance. We also discuss evidences that indicate the role of antimicrobials as signaling molecules in activating envelope stress responses.
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Affiliation(s)
- Sushovan Dam
- UMR_MD-1, Aix-Marseille Univ. & IRBA, 27 Boulevard Jean Moulin, 13005 Marseille, France
| | - Jean-Marie Pagès
- UMR_MD-1, Aix-Marseille Univ. & IRBA, 27 Boulevard Jean Moulin, 13005 Marseille, France
| | - Muriel Masi
- UMR_MD-1, Aix-Marseille Univ. & IRBA, 27 Boulevard Jean Moulin, 13005 Marseille, France
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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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Dual Regulation of the Small RNA MicC and the Quiescent Porin OmpN in Response to Antibiotic Stress in Escherichia coli. Antibiotics (Basel) 2017; 6:antibiotics6040033. [PMID: 29211019 PMCID: PMC5745476 DOI: 10.3390/antibiotics6040033] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 11/27/2017] [Accepted: 12/03/2017] [Indexed: 12/19/2022] Open
Abstract
Antibiotic resistant Gram-negative bacteria are a serious threat for public health. The permeation of antibiotics through their outer membrane is largely dependent on porin, changes in which cause reduced drug uptake and efficacy. Escherichia coli produces two major porins, OmpF and OmpC. MicF and MicC are small non-coding RNAs (sRNAs) that modulate the expression of OmpF and OmpC, respectively. In this work, we investigated factors that lead to increased production of MicC. micC promoter region was fused to lacZ, and the reporter plasmid was transformed into E. coli MC4100 and derivative mutants. The response of micC–lacZ to antimicrobials was measured during growth over a 6 h time period. The data showed that the expression of micC was increased in the presence of β-lactam antibiotics and in an rpoE depleted mutant. Interestingly, the same conditions enhanced the activity of an ompN–lacZ fusion, suggesting a dual transcriptional regulation of micC and the quiescent adjacent ompN. Increased levels of OmpN in the presence of sub-inhibitory concentrations of chemicals could not be confirmed by Western blot analysis, except when analyzed in the absence of the sigma factor σE. We suggest that the MicC sRNA acts together with the σE envelope stress response pathway to control the OmpC/N levels in response to β-lactam antibiotics.
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The multiple antibiotic resistance operon of enteric bacteria controls DNA repair and outer membrane integrity. Nat Commun 2017; 8:1444. [PMID: 29133912 PMCID: PMC5684230 DOI: 10.1038/s41467-017-01405-7] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 09/14/2017] [Indexed: 11/08/2022] Open
Abstract
The multiple antibiotic resistance (mar) operon of Escherichia coli is a paradigm for chromosomally encoded antibiotic resistance in enteric bacteria. The locus is recognised for its ability to modulate efflux pump and porin expression via two encoded transcription factors, MarR and MarA. Here we map binding of these regulators across the E. coli genome and identify an extensive mar regulon. Most notably, MarA activates expression of genes required for DNA repair and lipid trafficking. Consequently, the mar locus reduces quinolone-induced DNA damage and the ability of tetracyclines to traverse the outer membrane. These previously unrecognised mar pathways reside within a core regulon, shared by most enteric bacteria. Hence, we provide a framework for understanding multidrug resistance, mediated by analogous systems, across the Enterobacteriaceae. Transcription factors MarR and MarA confer multidrug resistance in enteric bacteria by modulating efflux pump and porin expression. Here, Sharma et al. show that MarA also upregulates genes required for lipid trafficking and DNA repair, thus reducing antibiotic entry and quinolone-induced DNA damage.
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Computational Analysis of the Molecular Mechanism of RamR Mutations Contributing to Antimicrobial Resistance in Salmonella enterica. Sci Rep 2017; 7:13418. [PMID: 29042652 PMCID: PMC5645378 DOI: 10.1038/s41598-017-14008-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 10/04/2017] [Indexed: 11/09/2022] Open
Abstract
Antimicrobial resistance (AMR) in pathogenic microorganisms with multidrug resistance (MDR) constitutes a severe threat to human health. A major causative mechanism of AMR is mediated through the multidrug efflux pump (MEP). The resistance-nodulation-division superfamily (RND family) of Gram-negative bacteria is usually the major cause of MDR in clinical studies. In Salmonella enterica, the RND pump is translated from the acrAB gene, which is regulated by the activator RamA. Many MEP-caused AMR strains have high ramA gene expression due to mutations in RamR, which has a homodimeric structure comprising the dimerization domain and DNA-binding domain (DBD). Three mutations on the dimerization domain, namely Y59H, M84I, and E160D, are far from the DBD; the molecular mechanism through which they influence RamR’s binding affinity to the ramA gene promoter and consequently disrupt RamA remains unclear. The present study conducted molecular dynamics simulations, binding free energy calculations, and normal mode analysis to investigate the mechanism through which Y59H, M84I, and E160D mutations on the dimerization domain influence the binding affinity of RamR to the ramA promoter. The present results suggest that the three mutations alter the RamR structure, resulting in decreased DNA-binding affinity.
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Miao M, Cao W, Wang H, Yan J, Wang M, Zheng Y, Xie X, Zhang X, Zhang H, Du H. ramR is not involved in the regulation of ramA associated antibiotic resistance in Salmonella enterica serovar Typhi. Microb Pathog 2017; 111:198-202. [DOI: 10.1016/j.micpath.2017.08.052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Revised: 08/20/2017] [Accepted: 08/30/2017] [Indexed: 11/16/2022]
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Zhang CZ, Chen PX, Yang L, Li W, Chang MX, Jiang HX. Coordinated Expression of acrAB-tolC and Eight Other Functional Efflux Pumps Through Activating ramA and marA in Salmonella enterica serovar Typhimurium. Microb Drug Resist 2017. [PMID: 28650690 DOI: 10.1089/mdr.2017.0086] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The aim of this study was to determine the expression of eight other functional transporter genes upon acrAB inactivation and also the expression of acrAB when the function of eight other transporters are impaired in Salmonella enterica. We used single- or multigene deletion mutants (i.e., ΔacrA, ΔacrB, ΔtolC, ΔacrAB, ΔacrEF, ΔacrD, ΔmdsABC, ΔmdtABC, ΔemrAB, ΔmacAB, ΔmdfA, ΔmdtK, ΔacrABramA, ΔacrABmarA, and ΔacrABsoxS) and real time (RT)-PCR to quantify the expression of different pump and regulator genes; infection ability was characterized by adhesion and invasion assays. The expression of acrAB operon was increased upon acrB inactivation. Single deletion of acrA or tolC also increased expression of acrB. The deletion of acrAB increased expression of eight other functional efflux pumps genes and vice versa, in which increased expression of ramA and marA was also detected. Mutants containing single deletions of functional pump genes were attenuated in cells. In conclusion, there is a feedback mechanism that coordinates regulation of AcrAB-TolC and eight other functional efflux pumps through the global transcriptional regulators ramA and marA in S. enterica serovar Typhimurium.
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Structural Alteration of OmpR as a Source of Ertapenem Resistance in a CTX-M-15-Producing Escherichia coli O25b:H4 Sequence Type 131 Clinical Isolate. Antimicrob Agents Chemother 2017; 61:AAC.00014-17. [PMID: 28264855 DOI: 10.1128/aac.00014-17] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 03/02/2017] [Indexed: 01/06/2023] Open
Abstract
In this study, an ertapenem-nonsusceptible Escherichia coli isolate was investigated to determine the genetic basis for its carbapenem resistance phenotype. This clinical strain was recovered from a patient that received, 1 year previously, ertapenem to treat a cholangitis due to a carbapenem-susceptible extended-spectrum-β-lactamase (ESBL)-producing E. coli isolate. Whole-genome sequencing of these strains was performed using Illumina and single-molecule real-time sequencing technologies. It revealed that they belonged to the ST131 clonal group, had the predicted O25b:H4 serotype, and produced the CTX-M-15 and TEM-1 β-lactamases. One nucleotide substitution was identified between these strains. It affected the ompR gene, which codes for a regulatory protein involved in the control of OmpC/OmpF porin expression, creating a Gly-63-Val substitution. The role of OmpR alteration was confirmed by a complementation experiment that fully restored the susceptibility to ertapenem of the clinical isolate. A modeling study showed that the Gly-63-Val change displaced the histidine-kinase phosphorylation site. SDS-PAGE analysis revealed that the ertapenem-nonsusceptible E. coli strain had a decreased expression of OmpC/OmpF porins. No significant defect in the growth rate or in the resistance to Dictyostelium discoideum amoeba phagocytosis was found in the ertapenem-nonsusceptible E. coli isolate compared to its susceptible parental strain. Our report demonstrates for the first time that ertapenem resistance may emerge clinically from ESBL-producing E. coli due to mutations that modulate the OmpR activity.
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Current perspectives on tigecycline resistance in Enterobacteriaceae: susceptibility testing issues and mechanisms of resistance. Int J Antimicrob Agents 2016; 48:11-18. [DOI: 10.1016/j.ijantimicag.2016.04.017] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Revised: 03/31/2016] [Accepted: 04/02/2016] [Indexed: 11/23/2022]
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Abstract
Tetracyclines possess many properties considered ideal for antibiotic drugs, including activity against Gram-positive and -negative pathogens, proven clinical safety, acceptable tolerability, and the availability of intravenous (IV) and oral formulations for most members of the class. As with all antibiotic classes, the antimicrobial activities of tetracyclines are subject to both class-specific and intrinsic antibiotic-resistance mechanisms. Since the discovery of the first tetracyclines more than 60 years ago, ongoing optimization of the core scaffold has produced tetracyclines in clinical use and development that are capable of thwarting many of these resistance mechanisms. New chemistry approaches have enabled the creation of synthetic derivatives with improved in vitro potency and in vivo efficacy, ensuring that the full potential of the class can be explored for use against current and emerging multidrug-resistant (MDR) pathogens, including carbapenem-resistant Enterobacteriaceae, MDR Acinetobacter species, and Pseudomonas aeruginosa.
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Molecular Characterization of Carbapenem-Nonsusceptible Enterobacterial Isolates Collected during a Prospective Interregional Survey in France and Susceptibility to the Novel Ceftazidime-Avibactam and Aztreonam-Avibactam Combinations. Antimicrob Agents Chemother 2015; 60:215-21. [PMID: 26482307 DOI: 10.1128/aac.01559-15] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 10/13/2015] [Indexed: 11/20/2022] Open
Abstract
An interregional surveillance program was conducted in the northwestern part of France to determine the prevalence of carbapenem-nonsusceptible Enterobacteriaceae (CNSE) isolates and their susceptibility to ceftazidime-avibactam and aztreonam-avibactam combinations. Nonduplicate CNSE clinical isolates were prospectively collected from six hospitals between June 2012 and November 2013. MICs of ceftazidime and aztreonam, alone or combined with a fixed concentration of avibactam (4 μg/ml), and those of carbapenems (comparator agents) were determined. MICs of ertapenem in combination with phenylalanine arginine-naphthylamide dihydrochloride (PAβN) were also determined to assess active efflux. Genes encoding carbapenemases, plasmid-mediated AmpC enzymes, extended-spectrum β-lactamases (ESBLs), and major outer membrane proteins (OMPs) were amplified and sequenced. OMPs were also extracted for SDS-PAGE analysis. Among the 139 CNSE isolates, mainly Enterobacter spp. and Klebsiella pneumoniae, 123 (88.4%) were ertapenem nonsusceptible, 12 (8.6%) exhibited reduced susceptibility to all carbapenems, and 4 Proteeae isolates (2.9%) were resistant to imipenem. Carbapenemase production was detected in only two isolates (producing OXA-48 and IMI-3). In contrast, OMP deficiency, in association with AmpCs and/or ESBLs (mainly CTX-M-9, SHV-12, and CTX-M-15), was largely identified among CNSE isolates. The ceftazidime-avibactam and aztreonam-avibactam combinations exhibited potent activity against CNSE isolates (MIC50/MIC90, 1/1 μg/ml and 0.5/0.5 μg/ml, respectively) compared to that of ceftazidime and aztreonam alone (MIC50/MIC90, 512/512 μg/ml and 128/512 μg/ml, respectively). This study reveals the in vitro activity of ceftazidime-avibactam and aztreonam-avibactam combinations against a large collection of porin-deficient enterobacterial isolates that are representative of the CNSE recovered in the northern part of France.
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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: 289] [Impact Index Per Article: 32.1] [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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Polymorphic variation in susceptibility and metabolism of triclosan-resistant mutants of Escherichia coli and Klebsiella pneumoniae clinical strains obtained after exposure to biocides and antibiotics. Antimicrob Agents Chemother 2015; 59:3413-23. [PMID: 25824225 DOI: 10.1128/aac.00187-15] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 03/21/2015] [Indexed: 01/08/2023] Open
Abstract
Exposure to biocides may result in cross-resistance to other antimicrobials. Changes in biocide and antibiotic susceptibilities, metabolism, and fitness costs were studied here in biocide-selected Escherichia coli and Klebsiella pneumoniae mutants. E. coli and K. pneumoniae mutants with various degrees of triclosan susceptibility were obtained after exposure to triclosan (TRI), benzalkonium chloride (BKC), chlorhexidine (CHX) or sodium hypochlorite (SHC), and ampicillin or ciprofloxacin. Alterations in antimicrobial susceptibility and metabolism in mutants were tested using Phenotype MicroArrays. The expression of AcrAB pump and global regulators (SoxR, MarA, and RamA) was measured by quantitative reverse transcription-PCR (qRT-PCR), and the central part of the fabI gene was sequenced. The fitness costs of resistance were assessed by a comparison of relative growth rates. Triclosan-resistant (TRI(r)) and triclosan-hypersusceptible (TRI(hs)) mutants of E. coli and K. pneumoniae were obtained after selection with biocides and/or antibiotics. E. coli TRI(r) mutants, including those with mutations in the fabI gene or in the expression of acrB, acrF, and marA, exhibited changes in susceptibility to TRI, CHX, and antibiotics. TRI(r) mutants for which the TRI MIC was high presented improved metabolism of carboxylic acids, amino acids, and carbohydrates. In TRI(r) mutants, resistance to one antimicrobial provoked hypersusceptibility to another one(s). TRI(r) mutants had fitness costs, particularly marA-overexpressing (E. coli) or ramA-overexpressing (K. pneumoniae) mutants. TRI, BKC, and CIP exposure frequently yielded TRI(r) mutants exhibiting alterations in AraC-like global regulators (MarA, SoxR, and RamA), AcrAB-TolC, and/or FabI, and influencing antimicrobial susceptibility, fitness, and metabolism. These various phenotypes suggest a trade-off of different selective processes shaping the evolution toward antibiotic/biocide resistance and influencing other adaptive traits.
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De Majumdar S, Yu J, Fookes M, McAteer SP, Llobet E, Finn S, Spence S, Monaghan A, Kissenpfennig A, Ingram RJ, Bengoechea J, Gally DL, Fanning S, Elborn JS, Schneiders T. Elucidation of the RamA regulon in Klebsiella pneumoniae reveals a role in LPS regulation. PLoS Pathog 2015; 11:e1004627. [PMID: 25633080 PMCID: PMC4310594 DOI: 10.1371/journal.ppat.1004627] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Accepted: 12/14/2014] [Indexed: 11/19/2022] Open
Abstract
Klebsiella pneumoniae is a significant human pathogen, in part due to high rates of multidrug resistance. RamA is an intrinsic regulator in K. pneumoniae established to be important for the bacterial response to antimicrobial challenge; however, little is known about its possible wider regulatory role in this organism during infection. In this work, we demonstrate that RamA is a global transcriptional regulator that significantly perturbs the transcriptional landscape of K. pneumoniae, resulting in altered microbe-drug or microbe-host response. This is largely due to the direct regulation of 68 genes associated with a myriad of cellular functions. Importantly, RamA directly binds and activates the lpxC, lpxL-2 and lpxO genes associated with lipid A biosynthesis, thus resulting in modifications within the lipid A moiety of the lipopolysaccharide. RamA-mediated alterations decrease susceptibility to colistin E, polymyxin B and human cationic antimicrobial peptide LL-37. Increased RamA levels reduce K. pneumoniae adhesion and uptake into macrophages, which is supported by in vivo infection studies, that demonstrate increased systemic dissemination of ramA overexpressing K. pneumoniae. These data establish that RamA-mediated regulation directly perturbs microbial surface properties, including lipid A biosynthesis, which facilitate evasion from the innate host response. This highlights RamA as a global regulator that confers pathoadaptive phenotypes with implications for our understanding of the pathogenesis of Enterobacter, Salmonella and Citrobacter spp. that express orthologous RamA proteins. Bacteria can rapidly evolve under antibiotic pressure to develop resistance, which occurs when target genes mutate, or when resistance-encoding genes are transferred. Alternatively, microbes can simply alter the levels of intrinsic proteins that allow the organism to “buy” time to resist antibiotic pressure. Klebsiella pneumoniae is a pathogen that causes significant blood stream or respiratory infections, but more importantly is a bacterium that is increasingly being reported as multidrug resistant. Our data demonstrate that RamA can trigger changes on the bacterial surface that allow Klebsiella to survive both antibiotic challenge, degradation by host immune peptides and resist phagocytosis. We demonstrate that the molecular basis of increased survival of ramA overexpressing K. pneumoniae, against host-derived factors is associated with RamA-driven alterations of the lipid A moiety of Klebsiella LPS. This modification is likely to be linked to Klebsiella’s ability to resist the host response so that it remains undetected by the immune system. The relevance of our work extends beyond RamA in Klebsiella as other pathogens such as Enterobacter spp and Salmonella spp. also produce this protein. Thus our overarching conclusion is that the intrinsic regulator, RamA perturbs host-microbe and microbe-drug interactions.
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Affiliation(s)
- Shyamasree De Majumdar
- Centre for Infection and Immunity, Belfast, United Kingdom
- Division of Pathway and Infection Medicine, Edinburgh, United Kingdom
| | - Jing Yu
- Centre for Infection and Immunity, Belfast, United Kingdom
| | - Maria Fookes
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Sean P. McAteer
- Division of Immunity and Infection, The Roslin Institute and R(D)SVS, The University of Edinburgh, Easter Bush, Midlothian, United Kingdom
| | - Enrique Llobet
- Laboratory Microbial Pathogenesis, Fundació d’Investigació Sanitària de les Illes Balears (FISIB) Recinto Hospital Joan March, Bunyola, Spain
| | - Sarah Finn
- UCD Centre for Molecular Innovation and Drug Discovery, School of Public Health, Physiotherapy & Population Science, University College Dublin, Dublin, Ireland
| | - Shaun Spence
- Centre for Infection and Immunity, Belfast, United Kingdom
| | - Avril Monaghan
- Centre for Infection and Immunity, Belfast, United Kingdom
| | | | | | - José Bengoechea
- Centre for Infection and Immunity, Belfast, United Kingdom
- Laboratory Microbial Pathogenesis, Fundació d’Investigació Sanitària de les Illes Balears (FISIB) Recinto Hospital Joan March, Bunyola, Spain
| | - David L. Gally
- Division of Immunity and Infection, The Roslin Institute and R(D)SVS, The University of Edinburgh, Easter Bush, Midlothian, United Kingdom
| | - Séamus Fanning
- UCD Centre for Molecular Innovation and Drug Discovery, School of Public Health, Physiotherapy & Population Science, University College Dublin, Dublin, Ireland
| | | | - Thamarai Schneiders
- Centre for Infection and Immunity, Belfast, United Kingdom
- Division of Pathway and Infection Medicine, Edinburgh, United Kingdom
- * E-mail:
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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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Fadli M, Chevalier J, Hassani L, Mezrioui NE, Pagès JM. Natural extracts stimulate membrane-associated mechanisms of resistance in Gram-negative bacteria. Lett Appl Microbiol 2014; 58:472-7. [PMID: 24447247 DOI: 10.1111/lam.12216] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 12/23/2013] [Accepted: 01/07/2014] [Indexed: 12/29/2022]
Abstract
UNLABELLED Several mechanisms are involved in the bacterial resistance towards antimicrobial agents. The membrane-associated mechanisms of resistance were studied in Escherichia coli strains after incubation with Thymus maroccanus essential oil, its major components (carvacrol and thymol) or with certain antibiotics. The minimum inhibitory concentration (MIC) and the expression of membrane proteins, porins and efflux pumps were determined in wild type and derivative strains. Derivative strains adapted to different compounds displayed a high level of resistance to all tested antibiotics. The MIC increase is associated with an overexpression of an efflux pump immunorelated to AcrAB-TolC in various variants. Interestingly, the expression of outer membrane proteins slightly decreases in these strains. We demonstrate that the increase in antibiotic resistance correlates with membrane changes observed in the variants. This type of bacterial adaptation to natural compounds can occur in vivo providing the emergence/selection of bacteria less susceptible to clinically used antibiotics. SIGNIFICANCE AND IMPACT OF THE STUDY Thymus maroccanus essential oil and some major components are able to select variants that modify the expression of transporters involved in the influx (porins) and in the efflux (AcrAB family) of various drugs. Importantly, these membrane proteins are involved in the transport of natural compounds and several antibiotic families. This special 'membrane adaptation' can explain the persistence of less susceptible/tolerant bacteria in the environment where natural compounds are present and the continuous stimulation of efflux systems in these bacteria.
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Affiliation(s)
- M Fadli
- UMR-MD1, Aix-Marseille University, IRBA, Marseille, France; Laboratory of Biology and Biotechnology of Microorganisms Faculty of Science, University Cadi Ayyad, Marrakech, Morocco
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The crystal structure of multidrug-resistance regulator RamR with multiple drugs. Nat Commun 2013; 4:2078. [PMID: 23800819 DOI: 10.1038/ncomms3078] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Accepted: 05/30/2013] [Indexed: 11/08/2022] Open
Abstract
RamR is a transcriptional repressor of the gene-encoding RamA protein, which controls the expression of the multidrug efflux system genes acrAB-tolC. RamR is an important multidrug-resistance factor, however, its structure and the identity of the molecules to which it responds have been unknown. Here, we report the crystal structure of RamR in complex with multiple drugs, including berberine, crystal violet, dequalinium, ethidium bromide and rhodamine 6G. All compounds are found to interact with Phe155 of RamR, and each compound is surrounded by different amino acid residues. Binding of these compounds to RamR reduces its DNA-binding affinity, which results in the increased expression of ramA. Our results reveal significant flexibility in the substrate-recognition region of RamR, which regulates the bacterial efflux participating in multidrug resistance.
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40
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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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Valade E, Davin-Regli A, Bolla JM, Pagès JM. Bacterial Membrane, a Key for Controlling Drug Influx and Efflux. Antibiotics (Basel) 2013. [DOI: 10.1002/9783527659685.ch9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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Masi M, Pagès JM. Structure, Function and Regulation of Outer Membrane Proteins Involved in Drug Transport in Enterobactericeae: the OmpF/C - TolC Case. Open Microbiol J 2013; 7:22-33. [PMID: 23569467 PMCID: PMC3617542 DOI: 10.2174/1874285801307010022] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Revised: 02/01/2013] [Accepted: 02/03/2013] [Indexed: 11/26/2022] Open
Abstract
Antibiotic translocation across membranes of Gram-negative bacteria is a key step for the activity on their specific intracellular targets. Resistant bacteria control their membrane permeability as a first line of defense to protect themselves against external toxic compounds such as antibiotics and biocides. On one hand, resistance to small hydrophilic antibiotics such as ß-lactams and fluoroquinolones frequently results from the « closing » of their way in: the general outer membrane porins. On the other hand, an effective way out for a wide range of antibiotics is provided by TolC-like proteins, which are outer membrane components of multidrug efflux pumps. Accordingly, altered membrane permeability, including porin modifications and/or efflux pumps’ overexpression, is always associated to multidrug resistance (MDR) in a number of clinical isolates. Several recent studies have highlighted our current understanding of porins/TolC structures and functions in Enterobacteriaceae. Here, we review the transport of antibiotics through the OmpF/C general porins and the TolC-like channels with regards to recent data on their structure, function, assembly, regulation and contribution to bacterial resistance. Because MDR strains have evolved global strategies to identify and fight our antibiotic arsenal, it is important to constantly update our global knowledge on antibiotic transport.
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Affiliation(s)
- Muriel Masi
- CNRS-UMR 8619, Institut de Biophysique et de Biochimie Moléculaire et Cellulaire (IBBMC), Université Paris Sud, Orsay, France
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Lawler AJ, Ricci V, Busby SJW, Piddock LJV. Genetic inactivation of acrAB or inhibition of efflux induces expression of ramA. J Antimicrob Chemother 2013; 68:1551-7. [PMID: 23493314 PMCID: PMC3682690 DOI: 10.1093/jac/dkt069] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Objectives The transcriptional activator RamA regulates production of the multidrug resistance efflux AcrAB–TolC system in several Enterobacteriaceae. This study investigated factors that lead to increased expression of ramA. Methods In order to monitor changes in ramA expression, the promoter region of ramA was fused to a gfp gene encoding an unstable green fluorescence protein (GFP) on the reporter plasmid, pMW82. The ramA reporter plasmid was transformed into Salmonella Typhimurium SL1344 and a ΔacrB mutant. The response of the reporter to subinhibitory concentrations of antibiotics, dyes, biocides, psychotropic agents and efflux inhibitors was measured during growth over a 5 h time period. Results Our data revealed that the expression of ramA was increased in a ΔacrB mutant and also in the presence of the efflux inhibitors phenylalanine-arginine-β-naphthylamide, carbonyl cyanide m-chlorophenylhydrazone and 1-(1-naphthylmethyl)-piperazine. The phenothiazines chlorpromazine and thioridazine also increased ramA expression, triggering the greatest increase in GFP expression. However, inducers of Escherichia coli marA and soxS and 12 of 17 tested antibiotic substrates of AcrAB–TolC did not induce ramA expression. Conclusions This study shows that expression of ramA is not induced by most substrates of the AcrAB–TolC efflux system, but is increased by mutational inactivation of acrB or when efflux is inhibited.
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Affiliation(s)
- A J Lawler
- Antimicrobials Research Group, School of Immunity and Infection, Institute of Microbiology and Infection, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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Collao B, Morales EH, Gil F, Calderón IL, Saavedra CP. ompW is cooperatively upregulated by MarA and SoxS in response to menadione. MICROBIOLOGY-SGM 2013; 159:715-725. [PMID: 23393149 PMCID: PMC3709825 DOI: 10.1099/mic.0.066050-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
OmpW is a minor porin whose biological function has not been clearly defined. Evidence obtained in our laboratory indicates that in Salmonella enterica serovar Typhimurium the expression of OmpW is activated by SoxS upon exposure to paraquat and it is required for resistance. SoxS belongs to the AraC family of transcriptional regulators, like MarA and Rob. Due to their high structural similarity, the genes under their control have been grouped in the mar/sox/rob regulon, which presents a DNA-binding consensus sequence denominated the marsox box. In this work, we evaluated the role of the transcription factors MarA, SoxS and Rob of S. enterica serovar Typhimurium in regulating ompW expression in response to menadione. We determined the transcript and protein levels of OmpW in different genetic backgrounds; in the wild-type and Δrob strains ompW was upregulated in response to menadione, while in the ΔmarA and ΔsoxS strains the induction was abolished. In a double marA soxS mutant, ompW transcript levels were lowered after exposure to menadione, and only complementation in trans with both genes restored the positive regulation. Using transcriptional fusions and electrophoretic mobility shift assays with mutant versions of the promoter region we demonstrated that two of the predicted sites were functional. Additionally, we demonstrated that MarA increases the affinity of SoxS for the ompW promoter region. In conclusion, our study shows that ompW is upregulated in response to menadione in a cooperative manner by MarA and SoxS through a direct interaction with the promoter region.
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Affiliation(s)
- B Collao
- Laboratorio de Microbiología Molecular, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile
| | - E H Morales
- Laboratorio de Microbiología Molecular, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile
| | - F Gil
- Laboratorio de Microbiología Molecular, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile
| | - I L Calderón
- Laboratorio de Microbiología Molecular, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile
| | - C P Saavedra
- Laboratorio de Microbiología Molecular, Facultad de Ciencias Biológicas, Universidad Andres Bello, Santiago, Chile
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Veleba M, De Majumdar S, Hornsey M, Woodford N, Schneiders T. Genetic characterization of tigecycline resistance in clinical isolates of Enterobacter cloacae and Enterobacter aerogenes. J Antimicrob Chemother 2013; 68:1011-8. [PMID: 23349441 DOI: 10.1093/jac/dks530] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
OBJECTIVES The intrinsically encoded ramA gene has been linked to tigecycline resistance through the up-regulation of efflux pump AcrAB in Enterobacter cloacae. The molecular basis for increased ramA expression in E. cloacae and Enterobacter aerogenes, as well as the role of AraC regulator rarA, has not yet been shown. To ascertain the intrinsic molecular mechanism(s) involved in tigecycline resistance in Enterobacter spp., we analysed the expression levels of ramA and rarA and corresponding efflux pump genes acrAB and oqxAB in Enterobacter spp. clinical isolates. METHODS The expression levels of ramA, rarA, oqxA and acrA were tested by quantitative real-time RT-PCR. The ramR open reading frames of the ramA-overexpressing strains were sequenced; strains harbouring mutations were transformed with wild-type ramR to study altered ramA expression and tigecycline susceptibility. RESULTS Tigecycline resistance was mediated primarily by increased ramA expression in E. cloacae and E. aerogenes. Only the ramA-overexpressing E. cloacae isolates showed increased rarA and oqxA expression. Upon complementation with wild-type ramR, all Enterobacter spp. containing ramR mutations exhibited decreased ramA and acrA expression and increased tigecycline susceptibility. Exceptions were one E. cloacae strain and one E. aerogenes strain, where a decrease in ramA levels was not accompanied by lower acrA expression. CONCLUSIONS Increased ramA expression due to ramR deregulation is the primary mediator of tigecycline resistance in clinical isolates of E. cloacae and E. aerogenes. However, some ramA-overexpressing isolates do not show changes in ramR, suggesting alternate pathways of ramA regulation; the rarA regulator and the oqxAB efflux pump may also play a role in tigecycline resistance in E. cloacae.
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Affiliation(s)
- Mark Veleba
- Centre for Infection and Immunity, Queen's University Belfast, Health Sciences Building, 97 Lisburn Road, Belfast BT9 7AE, UK
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Effect of transcriptional activators SoxS, RobA, and RamA on expression of multidrug efflux pump AcrAB-TolC in Enterobacter cloacae. Antimicrob Agents Chemother 2012; 56:6256-66. [PMID: 23006750 DOI: 10.1128/aac.01085-12] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Control of membrane permeability is a key step in regulating the intracellular concentration of antibiotics. Efflux pumps confer innate resistance to a wide range of toxic compounds such as antibiotics, dyes, detergents, and disinfectants in members of the Enterobacteriaceae. The AcrAB-TolC efflux pump is involved in multidrug resistance in Enterobacter cloacae. However, the underlying mechanism that regulates the system in this microorganism remains unknown. In Escherichia coli, the transcription of acrAB is upregulated under global stress conditions by proteins such as MarA, SoxS, and Rob. In the present study, two clinical isolates of E. cloacae, EcDC64 (a multidrug-resistant strain overexpressing the AcrAB-TolC efflux pump) and Jc194 (a strain with a basal AcrAB-TolC expression level), were used to determine whether similar global stress responses operate in E. cloacae and also to establish the molecular mechanisms underlying this response. A decrease in susceptibility to erythromycin, tetracycline, telithromycin, ciprofloxacin, and chloramphenicol was observed in clinical isolate Jc194 and, to a lesser extent in EcDC64, in the presence of salicylate, decanoate, tetracycline, and paraquat. Increased expression of the acrAB promoter in the presence of the above-described conditions was observed by flow cytometry and reverse transcription-PCR, by using a reporter fusion protein (green fluorescent protein). The expression level of the AcrAB promoter decreased in E. cloacae EcDC64 derivates deficient in SoxS, RobA, and RamA. Accordingly, the expression level of the AcrAB promoter was higher in E. cloacae Jc194 strains overproducing SoxS, RobA, and RamA. Overall, the data showed that SoxS, RobA, and RamA regulators were associated with the upregulation of acrAB, thus conferring antimicrobial resistance as well as a stress response in E. cloacae. In summary, the regulatory proteins SoxS, RobA, and RamA were cloned and sequenced for the first time in this species. The involvement of these proteins in conferring antimicrobial resistance through upregulation of acrAB was demonstrated in E. cloacae.
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Fadli M, Chevalier J, Bolla JM, Mezrioui NE, Hassani L, Pages JM. Thymus maroccanusessential oil, a membranotropic compound active on Gram-negative bacteria and resistant isolates. J Appl Microbiol 2012; 113:1120-9. [DOI: 10.1111/j.1365-2672.2012.05401.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Revised: 06/08/2012] [Accepted: 07/13/2012] [Indexed: 12/18/2022]
Affiliation(s)
| | - J. Chevalier
- UMR-MD1; Aix-Marseille Université; IRBA; Marseille; France
| | - J.-M. Bolla
- UMR-MD1; Aix-Marseille Université; IRBA; Marseille; France
| | - N.-E. Mezrioui
- Laboratory of Biology and Biotechnology of Microorganisms; Faculty of Science; University Cadi Ayyad; Marrakech; Morocco
| | - L. Hassani
- Laboratory of Biology and Biotechnology of Microorganisms; Faculty of Science; University Cadi Ayyad; Marrakech; Morocco
| | - J.-M. Pages
- UMR-MD1; Aix-Marseille Université; IRBA; Marseille; France
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Differential expression of the transcription factors MarA, Rob, and SoxS of Salmonella Typhimurium in response to sodium hypochlorite: down-regulation of rob by MarA and SoxS. Arch Microbiol 2012; 194:933-42. [PMID: 22752112 DOI: 10.1007/s00203-012-0828-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Revised: 06/01/2012] [Accepted: 06/08/2012] [Indexed: 10/28/2022]
Abstract
To survive, Salmonella enterica serovar Typhimurium (S. Typhimurium) must sense signals found in phagocytic cells and modulate gene expression. In the present work, we evaluated the expression and cross-regulation of the transcription factors MarA, Rob, and SoxS in response to NaOCl. We generated strains ΔsoxS and ΔmarA, which were 20 times more sensitive to NaOCl as compared to the wild-type strain; while Δrob only 5 times. Subsequently, we determined that marA and soxS transcript and protein levels were increased while those of rob decreased in a wild-type strain treated with NaOCl. To assess if changes in S. Typhimurium after exposure to NaOCl were due to a cross-regulation, as in Escherichia coli, we evaluated the expression of marA, soxS, and rob in the different genetic backgrounds. The positive regulation observed in the wild-type strain of marA and soxS was retained in the Δrob strain. As in the wild-type strain, rob was down-regulated in the ΔmarA and ΔsoxS treated with NaOCl; however, this effect was decreased. Since rob was down-regulated by both factors, we generated a ΔmarA ΔsoxS strain finding that the negative regulation was abolished, confirming our hypothesis. Electrophoretic mobility shift assays using MarA and SoxS confirmed an interaction with the promoter of rob.
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Nikaido E, Giraud E, Baucheron S, Yamasaki S, Wiedemann A, Okamoto K, Takagi T, Yamaguchi A, Cloeckaert A, Nishino K. Effects of indole on drug resistance and virulence of Salmonella enterica serovar Typhimurium revealed by genome-wide analyses. Gut Pathog 2012; 4:5. [PMID: 22632036 PMCID: PMC3405474 DOI: 10.1186/1757-4749-4-5] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Accepted: 05/25/2012] [Indexed: 11/10/2022] Open
Abstract
Background Many Gram-positive and Gram-negative bacteria produce large quantities of indole as an intercellular signal in microbial communities. Indole demonstrated to affect gene expression in Escherichia coli as an intra-species signaling molecule. In contrast to E. coli, Salmonella does not produce indole because it does not harbor tnaA, which encodes the enzyme responsible for tryptophan metabolism. Our previous study demonstrated that E. coli-conditioned medium and indole induce expression of the AcrAB multidrug efflux pump in Salmonella enterica serovar Typhimurium for inter-species communication; however, the global effect of indole on genes in Salmonella remains unknown. Results To understand the complete picture of genes regulated by indole, we performed DNA microarray analysis of genes in the S. enterica serovar Typhimurium strain ATCC 14028s affected by indole. Predicted Salmonella phenotypes affected by indole based on the microarray data were also examined in this study. Indole induced expression of genes related to efflux-mediated multidrug resistance, including ramA and acrAB, and repressed those related to host cell invasion encoded in the Salmonella pathogenicity island 1, and flagella production. Reduction of invasive activity and motility of Salmonella by indole was also observed phenotypically. Conclusion Our results suggest that indole is an important signaling molecule for inter-species communication to control drug resistance and virulence of S. enterica.
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Affiliation(s)
- Eiji Nikaido
- Laboratory of Microbiology and Infectious Diseases, Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, 567-00447, Japan.,Department of Cell Membrane Biology, Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, Japan.,Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - 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
| | - 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
| | - Suguru Yamasaki
- Laboratory of Microbiology and Infectious Diseases, Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, 567-00447, Japan.,Department of Cell Membrane Biology, Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, Japan.,Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - Agnès Wiedemann
- INRA, UMR1282 Infectiologie et Santé Publique, F-37380, Nouzilly, France.,Université François Rabelais de Tours, UMR1282 Infectiologie et Santé Publique, F-37000, Tours, France
| | - Kousuke Okamoto
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - Tatsuya Takagi
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - Akihito Yamaguchi
- Department of Cell Membrane Biology, Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, Japan.,Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - 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
| | - Kunihiko Nishino
- Laboratory of Microbiology and Infectious Diseases, Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, 567-00447, Japan
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Binding of the RamR repressor to wild-type and mutated promoters of the RamA gene involved in efflux-mediated multidrug resistance in Salmonella enterica serovar Typhimurium. Antimicrob Agents Chemother 2011; 56:942-8. [PMID: 22123696 DOI: 10.1128/aac.05444-11] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The transcriptional activator RamA is involved in multidrug resistance (MDR) by increasing expression of the AcrAB-TolC RND-type efflux system in several pathogenic Enterobacteriaceae. In Salmonella enterica serovar Typhimurium (S. Typhimurium), ramA expression is negatively regulated at the local level by RamR, a transcriptional repressor of the TetR family. We here studied the DNA-binding activity of the RamR repressor with the ramA promoter (P(ramA)). As determined by high-resolution footprinting, the 28-bp-long RamR binding site covers essential features of P(ramA), including the -10 conserved region, the transcriptional start site of ramA, and two 7-bp inverted repeats. Based on the RamR footprint and on electrophoretic mobility shift assays (EMSAs), we propose that RamR interacts with P(ramA) as a dimer of dimers, in a fashion that is structurally similar to the QacR-DNA binding model. Surface plasmon resonance (SPR) measurements indicated that RamR has a 3-fold-lower affinity (K(D) [equilibrium dissociation constant] = 191 nM) for the 2-bp-deleted P(ramA) of an MDR S. Typhimurium clinical isolate than for the wild-type P(ramA) (K(D) = 66 nM). These results confirm the direct regulatory role of RamR in the repression of ramA transcription and precisely define how an alteration of its binding site can give rise to an MDR phenotype.
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