Two new genes (mexXY) similar to mexAB, mexCD, and mexEF and mediating multidrug resistance were cloned from the chromosome of Pseudomonas aeruginosa. Elevated ethidium extrusion was observed with Escherichia coli cells harboring the plasmid carrying mexXY. This MexXY system confers higher resistance to fluoroquinolones than the MexAB and MexCD systems, and E. coli ToIC or P. aeruginosa OprM is...

Pseudomonas aeruginosa biofilms are intrinsically resistant to antimicrobial chemotherapies. At present, very little is known about the physiological changes that occur during the transition from the planktonic to biofilm mode of growth. The resistance of P. aeruginosa biofilms to numerous antimicrobial agents that are substrates subject to active efflux from planktonic cells suggests that effl...

BACKGROUND Mex efflux pumps contribute to multidrug resistance in Pseudomonas aeruginosa. Evidencing their expression in clinical isolates would help in rationalizing antibiotic selection. METHODS We have developed a combined phenotypic and genotypic approach for the differential diagnosis of resistance mediated by four major transporters (MexAB-OprM, MexCD-OprJ, MexEF-OprN, MexXY-OprM). The ...

The aim of this study was to detect the expression of 4 clinically-important efflux pumps in the Resistance-Nodulation-Cell Division (RND) family including MexAB-OprM, MexXY, MexCD-OprJ and MexEF-OprN in Pseudomonas aeruginosa using a combination of resistance-phenotypic markers and multiplex RT-PCR (mRT-PCR). The antibiotic substrates specific for each Mex systems were used as phenotypic marke...

Pseudomonas aeruginosa strains that overexpress mexCD-oprJ become hypersusceptible to imipenem. Disruption of AmpC induction has been suggested to cause this phenotype. However, data from this study demonstrate that hypersusceptibility to imipenem can develop without changes in ampC expression or AmpC activity. Furthermore, hypersusceptibility is not caused by changes in expression of the outer...

  Target modification and reduced drug accumulation are the main resistance mechanisms against fluoroquinolone antibiotics in Pseudomonas aeruginosa. We performed a genotypic characterization of three major Mex multidrug efflux pumps (MexAB-OprM, MexXY-OprM and MexCD-OprJ) in ciprofloxacin resistant clinical isolates of P. aeru­ginosa, collected from Tehran, Iran this was followed by sequencin...