scholarly journals Characterization of MexT, the Regulator of the MexE-MexF-OprN Multidrug Efflux System of Pseudomonas aeruginosa

1999 ◽  
Vol 181 (20) ◽  
pp. 6300-6305 ◽  
Author(s):  
Thilo Köhler ◽  
Simone F. Epp ◽  
Lasta Kocjancic Curty ◽  
Jean-Claude Pechère
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Cross Resistance ◽  
Multidrug Efflux ◽  
Efflux System ◽  
Quinone Oxidoreductase ◽  
Reading Frame ◽  
In The Wild ◽  
Posttranscriptional Level ◽  
Multidrug Efflux System

ABSTRACT We investigated the regulation of the MexEF-OprN multidrug efflux system of Pseudomonas aeruginosa, which is overexpressed innfxC-type mutants and confers resistance to quinolones, chloramphenicol and trimethoprim. Sequencing of the DNA region upstream of the mexEF-oprN operon revealed the presence of an open reading frame (ORF) of 304 amino acids encoding a LysR-type transcriptional activator, termed MexT. By using T7-polymerase, a 34-kDa protein was expressed in Escherichia coli from a plasmid carrying the mexT gene. Expression of amexE::lacZ fusion was 10-fold higher in nfxC-type mutants than in the wild-type strain; however, transcription of mexT as well as the mexT DNA region was unchanged. Located adjacent to mexT but transcribed in opposite direction, the beginning of an ORF termedqrh (quinone oxidoreductase homologue) was identified. Expression of a qrh::lacZ fusion was also found to be activated by MexT. Further, we present evidence for coregulation at the transcriptional and the posttranscriptional level between the MexEF-OprN efflux system and the OprD porin responsible for cross-resistance of nfxC-type mutants to carbapenem antibiotics.

scholarly journals Characterization of MexE–MexF–OprN, a positively regulated multidrug efflux system of Pseudomonas aeruginosa

1997 ◽  
Vol 23 (2) ◽  
pp. 345-354 ◽  
Author(s):  
Thilo Ko¨hler ◽  
Mehri Michéa‐Hamzehpour ◽  
Uta Henze ◽  
Naomasa Gotoh ◽  
Lasta Kocjancic Curty ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Multidrug Efflux ◽  
Efflux System ◽  
Multidrug Efflux System

scholarly journals Characterization of the MexC-MexD-OprJ Multidrug Efflux System in ΔmexA-mexB-oprM Mutants of Pseudomonas aeruginosa

1998 ◽  
Vol 42 (8) ◽  
pp. 1938-1943 ◽  
Author(s):  
Naomasa Gotoh ◽  
Hideto Tsujimoto ◽  
Masataka Tsuda ◽  
Kiyomi Okamoto ◽  
Atsuko Nomura ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Transcriptional Repression ◽  
Fourth Generation ◽  
Multidrug Efflux ◽  
Efflux System ◽  
Polyclonal Antisera ◽  
A Site ◽  
Specific Deletion ◽  
Multidrug Efflux System

ABSTRACT Expression of the multidrug efflux system MexC-MexD-OprJ innfxB mutants of Pseudomonas aeruginosacontributes to resistance to fluoroquinolones and the “fourth-generation” cephems (cefpirome and cefozopran), but not to most β-lactams, including the ordinary cephems (ceftazidime and cefoperazone). nfxB mutants also express a second multidrug efflux system, MexA-MexB-OprM, due to incomplete transcriptional repression of this operon by the mexR gene product. To characterize the contribution of the MexC-MexD-OprJ system to drug resistance in P. aeruginosa, a site-specific deletion method was employed to remove the mexA-mexB-oprM region from the chromosome of wild-type and nfxB strains ofP. aeruginosa. Characterization of mutants lacking themexA-mexB-oprM region clearly indicated that the MexC-MexD-OprJ efflux system is involved in resistance to the ordinary cephems as well as fluoroquinolones and the fourth-generation cephems but not to carbenicillin and aztreonam. Rabbit polyclonal antisera and murine monoclonal antibody against the components of the MexA-MexB-OprM system were prepared and used to demonstrate the reduced production of this efflux system in the nfxB mutants. Consistent with this, transcription of the mexA-mexB-oprM operon decreased in an nfxB mutant. This reduction appears to explain the hypersusceptibility of the nfxB mutant to β-lactams, including ordinary cephems.

scholarly journals Meropenem potentiation of aminoglycoside activity against Pseudomonas aeruginosa: involvement of the MexXY-OprM multidrug efflux system

2018 ◽  
Vol 73 (5) ◽  
pp. 1247-1255 ◽  
Author(s):  
Keith Poole ◽  
Christie Gilmour ◽  
Maya A Farha ◽  
Michael D Parkins ◽  
Rachael Klinoski ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Multidrug Efflux ◽  
Efflux System ◽  
Multidrug Efflux System

scholarly journals Multidrug efflux in intrinsic resistance to trimethoprim and sulfamethoxazole in Pseudomonas aeruginosa.

1996 ◽  
Vol 40 (10) ◽  
pp. 2288-2290 ◽  
Author(s):  
T Köhler ◽  
M Kok ◽  
M Michea-Hamzehpour ◽  
P Plesiat ◽  
N Gotoh ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Outer Membrane Proteins ◽  
Multiple Drug ◽  
Drug Efflux ◽  
Wild Type ◽  
Multidrug Efflux ◽  
Efflux System ◽  
Intrinsic Resistance ◽  
Wild Type Parent ◽  
Multidrug Efflux System

Pseudomonas aeruginosa possesses at least two multiple drug efflux systems which are defined by the outer membrane proteins OprM and OprJ. We have found that mutants overexpressing OprM were two- and eightfold more resistant than their wild-type parent to sulfamethoxazole (SMX) and trimethoprim (TMP), respectively. For OprJ-overproducing strains, MICs of TMP increased fourfold but those of SMX were unchanged. Strains overexpressing OprM, but not those overexpressing OprJ, became hypersusceptible to TMP and SMX when oprM was inactivated. The wild-type antibiotic profile could be restored in an oprM mutant by transcomplementation with the cloned oprM gene. These results demonstrate that the mexABoprM multidrug efflux system is mainly responsible for the intrinsic resistance of P. aeruginosa to TMP and SMX.

scholarly journals Involvement of the MexXY-OprM Efflux System in Emergence of Cefepime Resistance in Clinical Strains of Pseudomonas aeruginosa

2006 ◽  
Vol 50 (4) ◽  
pp. 1347-1351 ◽  
Author(s):  
Didier Hocquet ◽  
Patrice Nordmann ◽  
Farid El Garch ◽  
Ludovic Cabanne ◽  
Patrick Plésiat
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Resistance Mechanism ◽  
Epidemiological Studies ◽  
Teaching Hospitals ◽  
Wild Type ◽  
Multidrug Efflux ◽  
Efflux System ◽  
Clinical Strains ◽  
Rnd Transporter ◽  
Multidrug Efflux System

ABSTRACT Cefepime (FEP) and ceftazidime (CAZ) are potent β-lactam antibiotics with similar MICs (1 to 2 μg/ml) for wild-type strains of Pseudomonas aeruginosa. However, recent epidemiological studies have highlighted the occurrence of isolates more resistant to FEP than to CAZ (FEPr/CAZs profile). We thus investigated the mechanisms conferring such a phenotype in 38 clonally unrelated strains collected in two French teaching hospitals. Most of the bacteria (n = 32; 84%) appeared to stably overexpress the mexY gene, which codes for the RND transporter of the multidrug efflux system MexXY-OprM. MexXY up-regulation was the sole FEP resistance mechanism identified (n = 12) or was associated with increased levels of pump MexAB-OprM (n = 5) or MexJK (n = 2), synthesis of secondary β-lactamase PSE-1 (n = 10), derepression of cephalosporinase AmpC (n = 1), coexpression of both OXA-35 and MexJK (n = 1), or production of both PSE-1 and MexAB-OprM (n = 1). Down-regulation of the mexXY operon in seven selected strains by the plasmid-borne repressor gene mexZ decreased FEP resistance from two- to eightfold, thereby demonstrating the significant contribution of MexXY-OprM to the FEPr/CAZs phenotype. The six isolates of this series that exhibited wild-type levels of the mexY gene were found to produce β-lactamase PSE-1 (n = 1), OXA-35 (n = 4), or both PSE-1 and OXA-35 (n = 1). Altogether, these data provide evidence that MexXY-OprM plays a major role in the development of FEP resistance among clinical strains of P. aeruginosa.

scholarly journals Overexpression of the MexEF-OprN Multidrug Efflux System Affects Cell-to-Cell Signaling in Pseudomonas aeruginosa

2001 ◽  
Vol 183 (18) ◽  
pp. 5213-5222 ◽  
Author(s):  
Thilo Köhler ◽  
Christian van Delden ◽  
Lasta Kocjancic Curty ◽  
Mehri Michea Hamzehpour ◽  
Jean-Claude Pechere
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Efflux Pump ◽  
Homoserine Lactone ◽  
Wild Type ◽  
Multidrug Efflux ◽  
Efflux System ◽  
Sensing Systems ◽  
In The Wild ◽  
Type Mutant ◽  
Regulator Genes

ABSTRACT Intrinsic and acquired antibiotic resistance of the nosocomial pathogen Pseudomonas aeruginosa is mediated mainly by the expression of several efflux pumps of broad substrate specificity. Here we report that nfxC type mutants, overexpressing the MexEF-OprN efflux system, produce lower levels of extracellular virulence factors than the susceptible wild type. These include pyocyanin, elastase, and rhamnolipids, three factors controlled by the las and rhl quorum-sensing systems of P. aeruginosa. In agreement with these observations are the decreased transcription of the elastase genelasB and the rhamnosyltransferase genesrhlAB measured in nfxC type mutants. Expression of the lasR and rhlR regulator genes was not affected in the nfxC type mutant. In contrast, transcription of the C4-homoserine lactone (C4-HSL) autoinducer synthase gene rhlI was reduced by 50% in the nfxC type mutant relative to that in the wild type. This correlates with a similar decrease in C4-HSL levels detected in supernatants of the nfxC type mutant. Transcription of an rhlAB-lacZ fusion could be partially restored by the addition of synthetic C4-HSL andPseudomonas quinolone signal (PQS). It is proposed that the MexEF-OprN efflux pump affects intracellular PQS levels.

scholarly journals Mutations in PA3574 (nalD) Lead to Increased MexAB-OprM Expression and Multidrug Resistance in Laboratory and Clinical Isolates of Pseudomonas aeruginosa

2005 ◽  
Vol 49 (5) ◽  
pp. 1782-1786 ◽  
Author(s):  
Mara L. Sobel ◽  
Didier Hocquet ◽  
Lily Cao ◽  
Patrick Plesiat ◽  
Keith Poole
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Multidrug Resistance ◽  
Resistant Mutant ◽  
Multidrug Resistant ◽  
Clinical Isolates ◽  
Multidrug Efflux ◽  
Efflux System ◽  
Clinical Strains ◽  
Transposon Insertion ◽  
Multidrug Efflux System

ABSTRACT Mutations in genes mexR and nalC have previously been shown to drive overexpression of the MexAB-OprM multidrug efflux system in Pseudomonas aeruginosa. A transposon insertion multidrug-resistant mutant of P. aeruginosa overproducing MexAB-OprM was disrupted in yet a third gene, PA3574, encoding a probable repressor of the TetR/AcrR family that we have dubbed NalD. Clinical strains overexpressing MexAB-OprM but lacking mutations in mexR or nalC were also shown to carry mutations in nalD. Moreover, the cloned nalD gene reduced the multidrug resistance and MexAB-OprM expression of the transposon mutant and clinical isolates, highlighting the significance of the nalD mutations vis-à-vis MexAB-OprM overexpression in these isolates.

scholarly journals MexCD-OprJ Multidrug Efflux System of Pseudomonas aeruginosa: Involvement in Chlorhexidine Resistance and Induction by Membrane-Damaging Agents Dependent upon the AlgU Stress Response Sigma Factor

2008 ◽  
Vol 52 (12) ◽  
pp. 4478-4482 ◽  
Author(s):  
Sebastien Fraud ◽  
Aaron J. Campigotto ◽  
Zhilin Chen ◽  
Keith Poole
Keyword(s):  
Gene Expression ◽  
Pseudomonas Aeruginosa ◽  
Stress Response ◽  
Sigma Factor ◽  
Multidrug Efflux ◽  
Efflux System ◽  
Multidrug Efflux System

ABSTRACT The biocide chlorhexidine (CHX) as well as additional membrane-active agents were shown to induce expression of the mexCD-oprJ multidrug efflux operon, dependent upon the AlgU stress response sigma factor. Hyperexpression of this efflux system in nfxB mutants was also substantially AlgU dependent. CHX resistance correlated with efflux gene expression in various mutants, consistent with MexCD-OprJ being a determinant of CHX resistance.

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