Plasmid-Mediated Mechanism of Quinolone Resistance on E. coli Isolates from Different Clinical Samples

Quinolone antimicrobials are widely used in clinical medicine due to their wide spectrum with high tissue penetration and ease of use; but increasing resistance with clinical use appears to be common in some bacterial pathogens, including Escherichia coli (E.coli). The aim of this study was to investigate plasmid-mediated quinolone resistance determinants (PMQR) including, qnrA, qnrB, and qnrS as the emerging mechanisms of quinolone resistance of E.coli isolates from different clinical sites in Karbala province, Iraq. A total of ۲۰۰ clinical samples were collected from patients suffering from infections such as UTI, gastro enteritis (diarrhea), vaginitis, and wound infections; ۳۰ samples were diagnosed as E.coli clinical strain from both sexes and different ages after identification by biochemical test, VITEK-۲ compact system, and by molecular method using ۱۶Sr DNA marker. Antimicrobial susceptibility and minimal inhibition concentration (MIC) testing for nalidixic acid, norfloxacin, ciprofloxacin, levofloxacin, and gatifloxacin was performed using the broth microdilution method. All strains were screened for PMQR genes qnrA, qnrB, and qnrS by the PCR method after DNA extraction from tested clinical isolates of E.coli. The results showed that E. coli is largely isolated from vaginal (۴۰%) and urine (۳۲%) samples, followed by wound infections (۲۴%) and stools (۲۱%).The high occurrence rate of E. coli(۳۳.۳۳%) isolates was observed in participants aged ۳۱-۴۵ years, while a lower occurrence (۱۰%)was recorded in a group of ˃ ۶۰-year-old female participants. Females have a notably increased frequency of E.coli compared to males, with the female to male ratio being ۸۷%:۱۳%. Molecular investigation showed the total percentage of E.coli isolates harboring qnr genes to be ۲۱/۳۰ (۷۰%); this figure is composed of ۱۴/۳۰ isolates harboring qnr in combined or mixed form (۴۶.۶۶%) and ۷/۳۰ (۲۳.۳۳%) isolates harboring qnr in single form (۳ isolates harboring qnrA alone, ۱ isolate harboring qnrB alone, ۳ isolates harboring qnrS alone).The prevalence rates of qnrA, qnrB, and qnrS were ۴۰%, ۴۳.۳۳%, and ۵۳.۳۳%, respectively. The results also showed that among E.coli isolates encoding qnr genes A, B, and S, ۲۴%, ۱۲%, and ۳۶% were resistant to nalidixic acid, respectively. Among those isolates carrying qnrA, qnrB, and qnrS genes, ۱۵.۸%, ۵.۳%, and ۲۶.۳%, respectively, were resistant to ciprofloxacin. Moreover, Norfloxacin resistance was seen in ۲۰.۰%, ۵.۰%, and ۳۰.۰% of E.coli isolates harboring qnr A, B, and S genes, respectively. Levofloxacin resistance was seen in ۳۷.۵%, ۷۵.۰%, and ۳۷.۵% of the isolates carrying the qnrA, qnrB, and qnrS genes, respectively. The lowest resistance rates of qnrA, B, and S-positive E.coli strains were against gatifloxacin (۰,۰, and ۲۵%, respectively).A high prevalence of qnr genes enhances the increasing resistance rate of E.coli against the quinolone antibiotic under study.

کلیدواژه ها:

Qnr ، Quinolone antibiotics ، E.coli ، Plasmid mediated resistance