Evaluation of Plasmid-Mediated ‎Quinolone Resistance Genes and ‎Biofilm Formation in Clinical ‎Isolates of Escherichia coli

Escherichiacoli is an opportunistic pathogenic bacterium that causes numerous diseases in humans and animals.Because of increased resistance to antibiotics, this bacterium has raised many concerns in the livestock industry as well as in medicine. The aim of this study was to determine the resistance to fluoroquinolones, to identify plasmid-mediated quinolone resistance (PMQR) genes and to determine the biofilm formation ability of E. coli strains isolated from human and bovine samples in Hamadan.In this descriptive study, 40 isolates of E. coli(20 human isolates, 20 bovine isolates) were studied. First, the resistance of the isolates to ciprofloxacin and levofloxacin was measured by microdilution broth method, and then the identification of fluoroquinolone resistance genes (qnrA, qnrB, qnrC, qnrD, qnrS and acc) was performed by PCR method. In the following, the ability of E. coli isolates to produce biofilm was evaluated by microtiter plate method and the results were analyzed by chi-square test using SPSS software (version 19). Microdilution results showed of 40 E.coli isolates, 26 (65%) were resistant to ciprofloxacin and 23 (57.5%) were found to be resistant to levofloxacin.In PMQR genes frequency analysis by PCR,the qnrA, qnrB, qnrC,qnrD, qnrS and aac genes were detected in 45%, 47.5%, 67.5%, 27.5%, 60% and 55% of the isolates, respectively. Also microtiter plate test results showed that 40% of the isolates were capable of forming strong biofilm and only 4% did not form biofilm.The results of the present study showed that the main mechanism of resistance to fluoroquinolones is related to PMQR genes and possibly excessive use of fluoroquinolones in human infections leads to the development of resistance to these drugs.Biofilm formation has also been shown to be effective in creating fluoroquinolone resistance.