objective(s): the major antibiotic efflux pump of esherichia coli is acrab-tolc. the first part of the pump, acrab, is encoded by acrab operon. the expression of this operon can be kept elevated by overexpression of an activator, mara following inactivation of marr and acrr repressors due to mutation in encoding genes, marr and acrr, respectively. the aims of this research were to use e. coli m...

A spontaneous mutant (M113) of Escherichia coli AG100 with an unstable multiple antibiotic resistance (Mar) phenotype was isolated in the presence of tetracycline. Two mutations were found: an insertion in the promoter of lon (lon3::IS186) that occurred first and a subsequent large tandem duplication, dupIS186, bearing the genes acrAB and extending from the lon3::IS186 to another IS186 present ...

The mexCD-oprJ and mexAB-oprM operons encode components of two distinct multidrug efflux pumps in Pseudomonas aeruginosa. To assess the contribution of individual components to antibiotic resistance and substrate specificity, these operons and their component genes were cloned and expressed in Escherichia coli. Western immunoblotting confirmed expression of the P. aeruginosa efflux pump compone...

The efflux pump AcrAB is important in the antibiotic resistance and virulence of several pathogenic bacteria. We report that deletion of the Yersinia pestis AcrAB-TolC homolog leads to increased susceptibility to diverse substrates, including, though unlike in Escherichia coli, the aminoglycosides. Neither is the Y. pestis pump affected by the efflux pump inhibitor phenylalanine-arginine beta-n...

The relationship between efflux system overexpression and cross-resistance to cefoxitin, quinolones, and chloramphenicol has recently been reported in Klebsiella pneumoniae. In 3 previously published clinical isolates and 17 in vitro mutants selected with cefoxitin or fluoroquinolones, mutations in the potential regulator genes of the AcrAB efflux pump (acrR, ramR, ramA, marR, marA, soxR, soxS,...

The objective of this study was to evaluate collateral sensitivity and cross-resistance antibiotic-induced resistant Salmonella Typhimurium various antibiotics. S. ATCC 19585 (STWT) exposed ciprofloxacin, gentamicin, kanamycin, tetracycline induce antibiotic resistance, respectively, assigned as STCIP, STGEN, STKAN, STTET. susceptibilities the mutants cefotaxime, chloramphenicol, polymyxin B, s...

  Objective(s): The major antibiotic efflux pump of Esherichia coli is AcrAB-TolC. The first part of the pump, AcrAB, is encoded by acrAB operon. The expression of this operon can be kept elevated by overexpression of an activator, MarA following inactivation of MarR and AcrR repressors due to mutation in encoding genes, marR and acrR, respectively. The aims of this research were to us...

The evolution of resistance to a single antibiotic is frequently accompanied by increased resistance to multiple other antimicrobial agents. In sharp contrast, very little is known about the frequency and mechanisms underlying collateral sensitivity. In this case, genetic adaptation under antibiotic stress yields enhanced sensitivity to other antibiotics. Using large-scale laboratory evolutiona...