AcrAB-TolC is the major multidrug efflux system in Enterobacteriaceae recognizing structurally unrelated molecules including antibiotics, dyes, and detergents. Additionally, in Escherichia coli it mediates resistance to bile salts. In the plant pathogen Erwinia amylovora AcrAB-TolC is required for virulence and phytoalexin resistance. Exchange analysis of AcrAB-TolC was conducted by complementi...

OBJECTIVES We conducted a study to determine the role played by amino acid mutations in DNA gyrase and topoisomerase IV, and the AcrAB efflux pump in resistance to fluoroquinolones in clinical isolates of Proteus mirabilis. METHODS Nine clinical isolates of P. mirabilis containing eight fluoroquinolone-resistant isolates and one fluoroquinolone-susceptible isolate as the causative pathogen we...

Active efflux pump is a primary fluoroquinolone resistant mechanism of clinical isolates of Salmonella enterica serovar Typhimurium. RamA is an essential element in producing multidrug resistant (MDR) S. enterica serovar Typhimurium. The aim of the present study was to elucidate the roles of RamA on the development of ciprofloxacin, the first choice for the treatment of salmonellosis, resistanc...

OBJECTIVE To investigate the contribution of gyrA mutation and efflux pumps to fluoroquinolone resistance and multidrug resistance among Escherichia coli isolates from dogs and cats. SAMPLE POPULATION 536 clinical isolates of E coli. PROCEDURES Minimum inhibitory concentrations (MICs) were determined for enrofloxacin and 6 other drug classes by use of broth microdilution techniques. Real-ti...

BACKGROUND & OBJECTIVES There is a worldwide emergence of fluoroquinolone resistance in Shigella species. To understand the molecular mechanisms associated with fluoroquinolone resistance, naturally occurring fluoroquinolone-resistant strains and laboratory-induced spontaneous mutants of Shigella spp. were used and the relative contributions of acrAB-tolC efflux pumps, gyrase and topoisomerase ...

Appearance of bacteria resistant to antibacterial agents puts physicians in trouble and threatens the health of the world. The rapid development of bacterial resistance in Escherichia coli to ciprofloxacin makes difficult the treatment of infectious diseases. So, detection of the locations of possible mutations in gyrase A gene ( gyrA ) in these mutants is very important to determine the mech...

AcrAB-TolC is a major efflux pump in Escherichia coli. It was reported that tolC is overexpressed and involves in improving the organic solvent tolerance level in Escherichia coli marR mutants that are resistant to several antibiotics, such as ciprofloxacin. Low and intermediate levels resistance did not improve organic solvent tolerance. Thus, in this descriptive-experimental study it was deci...

About 10% of the nalidixic acid-resistant (Nal(r)) mutants in a transposition-induced library exhibited a growth factor requirement as the result of cysH, icdA, metE, or purB mutation. Resistance in all of these mutants required a functional AcrAB-TolC efflux pump, but the EmrAB-TolC pump played no obvious role. Transcription of acrAB was increased in each type of Nal(r) mutant. In the icdA and...