Virotyping, genotyping, and molecular characterization of multidrug resistant Escherichia coli isolated from diarrheal patients of Bangladesh

Multidrug-resistant (MDR) Escherichia coli has been previously detected in other locations, but not in Chhatak, a diarrhea endemic region of Bangladesh. In this study, 36 E. coli isolated from diarrhea stools of adults and children from Chhatak were investigated for the prevalence of drug resistance, virulence and resistance related genes, genotyping, and other molecular characteristics. Antibiotic resistance profiling was performed by disk diffusion method whereas the presence of virulence genes, mobile genetic elements, plasmids, and resistance-related genes were monitored by PCR assay. Multiple resistance to drugs was observed in 94.4% of the isolates and 24 (66.7%) of the strains were found as enterotoxigenic E. coli (ETEC) pathogroup. Genotyping by ERIC-PCR fingerprinting revealed genetic heterogeneity among the MDR E. coli strains. Overall, 88% of E. coli strains possessed plasmids ranging from 0.6 to 140 MDa. Of the detected integrases (69%), intl1 was predominant (53%). Erythromycin esterase-B (ereB) was present in 8 out of 36 macrolide resistant strains (22%). Of 27 beta-lactam resistant isolates, 70%, 41%, and 33% carried blaCTX-M-1, blaTEM, and blaOXA, respectively. Of 23 tetracycline resistant strains, 13 tetB (57%) and 8 tetA (35%) were detected. All 24 ciprofloxacin resistant strains tested positive for gyrA, but none for qnrA. Sequence analysis of the quinolone resistance-determining regions (QRDR) of gyrA of two ciprofloxacin resistant strains showed two point mutations (S83L, D87N). Computational docking studies revealed a decreased interaction of the drug with the target due to this mutation. In conclusion, high incidence of plasmids and antimicrobial resistance in E. coli carrying virulence genes and resistance markers for antimicrobial drugs in diarrheagenic patients of Bangladesh is alarming as lateral transfer of these virulence and resistance genes in other infectious agents can make them irresistible, and infection control more challenging in the days to come. •Abundance of ETEC virotypes among MDR E. coli•Genetic heterogeneity depicted by ERIC-PCR fingerprinting•High carriage of plasmid, integrons and SXT elements•ereB, blaCTX-M-1, tetB and gyrA are the major resistance marker genes.•Fluoroquinolone resistance caused by two point mutations (S83L, D87N) in the QRDRs of gyrA gene