Abundance of Mobilized Colistin Resistance Gene ( <i>mcr-1</i> ) in Commensal <i>Escherichia coli</i> from Diverse Sources

Abstract

<b><i>Aims:</i></b> Antimicrobial resistance (AMR) spreads not only by pathogenic but also by commensal bacteria, and the latter can become a reservoir for resistance genes. This study was aimed to investigate the AMR patterns along with the presence of mobilized colistin resistance (<i>mcr</i>) genes in commensal <i>Escherichia coli</i> circulating in chickens, farm environments, street foods, and human patients. <b><i>Materials and Methods:</i></b> By a cross-sectional survey, isolates obtained from 530 samples were tested for their AMR profiles against 9 antimicrobials. Minimum inhibitory concentration (MIC) of the phenotypically colistin-resistant isolates was determined and screened for a set of <i>mcr</i> genes followed by sequencing of <i>mcr-1</i> gene in the multidrug-resistant (MDR) isolates. <b><i>Results:</i></b> A total of 313 <i>E. coli</i> strains were isolated and confirmed by polymerase chain reaction. Antimicrobial susceptibility testing revealed that about 98% (confidence interval [95% CI] 95-99) of the isolates were MDR, and 58% (95% CI 52-63) isolates exhibited resistance to colistin. MIC values of colistin against the isolates ranged from 4 to 64 mg/L. Except for human patients, 20.4% colistin-resistant isolates from other sources of isolation had <i>mcr-1</i> gene. <b><i>Conclusions:</i></b> There is abundance of commensal MDR <i>E. coli</i> strains with the acquisition of <i>mcr-1</i> gene circulating in chickens and farm environments in Bangladesh.