High prevalence of plasmid-mediated quinolone resistance

Fluro(quinolones) is an important class of antibiotic used widely in both human and veterinary medicine. Resistance to fluro(quinolones) can be acquired by either chromosomal point mutations or plasmid-mediated quinolone resistance (PMQR). There is a lack of studies on the prevalence of PMQR in organisms from environmental sources in Bangladesh. In this study, we investigated the occurrence of PMQR genes in E. coli from various water sources and analysed associations between multi-drug resistance (MDR) and resistance to extended spectrum [beta]-lactam antibiotics. We analysed 300 E. coli isolates from wastewaters of urban live-bird markets (n = 74) and rural households (n = 80), rural ponds (n = 71) and river water samples (n = 75) during 2017-2018. We isolated E. coli by filtering 100 ml of water samples through a 0.2[mu]m cellulose membrane and incubating on mTEC agar media followed by identification of isolated colonies using biochemical tests. We selected one isolate per sample for detection of PMQR genes by multiplex PCR and tested for antibiotic susceptibility by disc diffusion. Clonal relatedness of PMQR-positive isolates was evaluated by enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR). About 66% (n = 199) of E. coli isolates harbored PMQR-genes, predominantly qnrS (82%, n = 164) followed by aac(6')-lb-cr (9%, n = 17), oqxAB (7%, n = 13), qnrB (6%, n = 11) and qepA (4%, n = 8). Around 68% (n = 135) of PMQR-positive isolates were MDR and 92% (n = 183) were extended spectrum [beta]-lactamase (ESBL)-producing of which the proportion of positive samples was 87% (n = 159) for bla.sub.CTX-M-1' 34% (n = 62) for bla.sub.TEM, 9% (n = 16) for bla.sub.OXA-1, bla.sub.OXA-47 and bla.sub.CMY-2, and 2% (n = 4) for bla.sub.SHV . Further, 16% (n = 32) of PMQR-positive isolates were resistant to carbapenems of which 20 isolates carried bla.sub.NDM-1 . Class 1 integron (int1) was found in 36% (n = 72) of PMQR-positive E. coli isolates. PMQR genes were significantly associated with ESBL phenotypes (p[less than or equal to]0.001). The presence of several PMQR genes were positively associated with ESBL and carbapenemase encoding genes such as qnrS with bla.sub.CTXM-1 (p