Retrospective analysis of 189 nonredundant strains of Pseudomonas aeruginosa sequentially recovered from the sputum samples of 46 cystic fibrosis (CF) patients over a 10-year period (1998 to 2007) revealed that 53 out of 189 (28%) samples were hypersusceptible to the beta-lactam antibiotic ticarcillin (MIC < or = 4 microg/ml) (phenotype dubbed Tic(hs)). As evidenced by trans-complementation and...

The MexA-MexB-OprM efflux pump of Pseudomonas aeruginosa consists of two inner membrane proteins, MexA and MexB, and one outer membrane protein, OprM. We investigated the role of the components of this drug extrusion system by evaluating the repercussions of deleting these subunit components on the accumulation of several fluorescent probes. Fluorescence intensities of positively charged 2-(4-d...

A Pseudomonas aeruginosa strain carrying an insertion of an omega Hg interposon in the mexB gene (mexB::omega Hg; strain K879) produced markedly reduced but still detectable levels of OprM, the product of the third gene of the mexAB-oprM multidrug efflux operon. By using a lacZ transcriptional fusion vector, promoter activity likely responsible for OprM expression in the mexB::omega Hg mutant w...

Pseudomonas aeruginosa, one of the majority common opportunistic infections, has become a public health concern, exhibiting intrinsic and acquired resistance to wide range antimicrobials. The present work aimed study correlation between P. aeruginosa efflux pump mexAB-oprM genes antibiotic different types antibiotics. All 79 isolates were screened by chromogenic agar, which was used as selectiv...

For any positive integer parameters a and b, the second author recently introduced a generalization mexb of the standard minimum excludant mex = mex1, along with a game NIM(a, b) that extends further Fraenkel’s NIM = NIM(a, 1), which in its turn is a generalization of the classical Wythoff NIM = NIM(1, 1). It was shown that P-positions (the kernel) of NIM(a, b) are given by the following typica...

The Escherichia coli AcrB efflux pump is a resistance-nodulation-division (RND) pump that recognizes many unrelated compounds (9, 10). AcrB forms a complex with AcrA and TolC and is the single most important contributor to multidrug resistance in E. coli. Crystallographic models suggest that AcrB forms an asymmetric trimer in which each protomer corresponds to a distinct functional state of a p...

The β-lactam antibiotic temocillin (6-α-methoxy-ticarcillin) shows stability to most extended spectrum β-lactamases, but is considered inactive against Pseudomonas aeruginosa. Mutations in the MexAB-OprM efflux system, naturally occurring in cystic fibrosis (CF) isolates, have been previously shown to reverse this intrinsic resistance. In the present study, we measured temocillin activity in a ...

The Escherichia coli AcrB efflux pump is a resistance-nodulation-division (RND) pump that recognizes many unrelated compounds (9, 10). AcrB forms a complex with AcrA and TolC and is the single most important contributor to multidrug resistance in E. coli. Crystallographic models suggest that AcrB forms an asymmetric trimer in which each protomer corresponds to a distinct functional state of a p...

Multidrug membrane transporters (efflux pumps) can selectively extrude a variety of structurally and functionally diverse substrates (e.g., chemotoxics, antibiotics), leading to multidrug resistance (MDR) and ineffective treatment of a wide variety of diseases. In this study, we have designed and constructed a fusion gene (egfp-mexB) of N-terminal mexB with C-terminal egfp, inserted it into a p...