The AcrAB-TolC efflux pump plays an intrinsic role in resistance to hydrophobic solvents in Escherichia coli. E. coli OST5500 is hypersensitive to solvents due to inactivation of the acrB gene by insertion of IS30. Suppressor mutants showing high solvent resistance were isolated from OST5500. These mutants produced high levels of AcrE and AcrF proteins, which were not produced in OST5500, and i...

Many laboratory strains of Escherichia coli are resistant to methotrexate (MTX), a folate analogue that binds dihydrofolate reductase (DHFR). Mutations that inactivate either tolC or acrA confer MTX sensitivity. Further, overexpression of a fusion protein with DHFR activity reverses this sensitivity by titrating out intracellular MTX. These results suggest that MTX accumulates in cells where mu...

Fluoroquinolone resistance was characterized in Escherichia coli O78:K80 isolated from diseased turkeys. The level of resistance to fluoroquinolones of the isolates appeared closely correlated with substitutions in GyrA and ParC, but not with the production of the AcrAB efflux pump. Among isolates highly resistant to ciprofloxacin (MIC 8 mg/L) and harbouring identical substitutions (two in GyrA...

Efflux pump inhibitors (EPIs) are attractive compounds to reverse multidrug-resistance in clinically relevant bacterial pathogens. In this study we tested the ability of the neuroleptic drug pimozide to inhibit the Escherichia coli AcrAB-TolC efflux pump, whose overproduction confers resistance to various antimicrobial agents. A real-time Nile red efflux assay in the AcrAB - overproducing strai...

Awareness of the problem of antimicrobial resistance (AMR) has escalated and drug-resistant infections are named among the most urgent problems facing clinicians today. Our experiments here identify a transporter interactome and portray its essential function in acquisition of antimicrobial resistance. By exposing E. coli cells to consecutive increasing concentrations of the fluoroquinolone nor...

BACKGROUND Haemophilus influenzae HMC-C with high-level macrolide resistance after multi-step selection by clarithromycin reverted spontaneously and became hypersusceptible to macrolides. OBJECTIVE Determination of macrolide resistance mechanism(s) in hypersusceptible and hyperresistant strains. METHODS The presence of macrolide efflux in the strains was studied by radioactive erythromycin ...

OBJECTIVES To study the role of TolC and of parC mutation in high-level fluoroquinolone resistance in clonal clinical strains of Salmonella enterica serotype Typhimurium phage type DT204 (S. Typhimurium DT204). METHODS Deletion of the tolC gene (DeltatolC) was first performed in a susceptible S. Typhimurium DT104 strain lacking target gene mutations involved in fluoroquinolone resistance. P22...

MarA47(Yp) from Yersinia pestis, showing 47% identity to Escherichia coli MarA in its N terminus, caused resistance to antibiotics and to organic solvents when expressed in both E. coli and Y. pestis. Resistance was linked to increased expression of the AcrAB multidrug efflux pump. In four of five spontaneous multidrug-resistant mutants of Y. pestis independently selected by growth on tetracycl...

Mutants of Escherichia coli selected for resistance to the disinfectant pine oil or to a household product containing pine oil also showed resistance to multiple antibiotics (tetracycline, ampicillin, chloramphenicol, and nalidixic acid) and overexpressed the marA gene. Likewise, antibiotic-selected Mar mutants, which also overexpress marA, were resistant to pine oil. Deletion of the mar or acr...