Mobilized colistin resistance genes and selected tet genes in multidrug resistant Escherichia coli circulating in poultry, food and human sources in Bangladesh

The antimicrobial resistance (AMR) is rapidly spreading not only in pathogenic but also in commensal bacteria. Consequently, the latter becomes a reservoir pool for resistance genes, contributing to their transfer to other zoonotic pathogens over time. A cross-sectional survey was conducted to investigate the AMR patterns along with the presence of the mobilized colistin resistance (mcr) genes and three selected tet genes in commensal Escherichia coli circulating in poultry, street food and human sources. A total of 530 samples were investigated. Of them 150 (cloacal swabs) were from broiler chickens, 150 from different matrices (litter, feed, water and soil) at poultry farm environments, 152 (stool samples) from humans suffering from clinical illness and 78 from street foods. All the E. coli isolates obtained from the survey were tested for their susceptibility to a panel of nine antimicrobials. Univariable and multivariate logistic regression analyses were performed to identify risk factors associated with the presence of colistin- and tetracycline-resistant E. coli. In total, 316 E. coli strains were obtained comprising 134, 80, 75 and 27 respectively, from broiler chicken, farm environment, human and street food samples. Of all the isolates 98% (95% CI 95-99) were found to be multidrug registrant (MDR), 58% (95% CI 52-63) showed resistance to colistin, and 98% (95% CI 96-99) to tetracycline. Among the colistin-resistant isolates, 37% were positive for at least one of the four mcr genes (mcr-1, mcr-2, mcr-3 and mcr-4) investigated. However, none of the human-origin isolates tested positive for any of the mcr genes. Among the tetracycline-resistant isolates, 59%, 15% and 6% had the tetA, tetB and tetC gene, respectively. The “antibiotic use” was positively associated with the presence of colistin-resistant E. coli in humans (OR 6.96; 95% CI 2.85-18.33; p<0.001). The same association was also found for the tetracycline-resistant E. coli in humans (OR 10.81; 95% CI 3.95-32.75; p<0.001). Treatment of diseases attributed to MDR- pathogens might be more challenging if the mcr genes from E. coli of poultry origin, as revealed in the study, are transferred to them.