Antimicrobial resistance in fecal Escherichia coli isolated from poultry chicks in northern Iran

Background: The use of antibiotics in food-producing animals has raised concerns about the spread of resistant bacteria. Antimicrobial resistance is achieved by horizontal gene transfer between bacteria or mobile gene elements in humans, animals and the environment. The present study was conducted to determine the prevalence and genetic diversity of antibiotic resistance in poultry-isolated E. coli in northern Iran. Materials and methods: Overall, 206 E. coli isolates were collected from the cloacal swabs of healthy Ross broiler chickens at 20-45 days of age from individual commercial broilers farms from August to December 2019. The antimicrobial susceptibility assessment was tested using disc diffusion for 20 antibiotics. PCRs were performed for investigating the respective antimicrobial resistance genes. Results: Among 206 fecal E. coli isolates, 89.81% were resistance to at least one antimicrobials tested, and 70.87% showed OR phenotype. The highest resistance was related to Flumequine and Chlortetracycline. In accordance with phenotypic assay, tetA, tetB, qnrS and qnrB encoding for tetracyclines and quinolones resistance were the most predominant genes. IMP, VIM, GIM and SPM beta-lactamase-encoding genes and colistin resistance-associated mcr genes were not detected in any phenotypically non susceptible isolates. Conclusion: The presence of different classes of resistance genes in poultry isolated E. coli strains suggests the importance of poultry-source E. coli in the distribution of drug resistance in humans in northern Iran.