Distribution pattern of antibiotic resistance genes in Escherichia coli isolated from colibacillosis cases in broiler farms of Egypt

BACKGROUND AND AIM: Multidrug resistance (MDR) of Escherichia coli has become an increasing concern in poultry farming worldwide. However, E. coli can accumulate resistance genes through gene transfer. The most problematic resistance mechanism in E. coli is the acquisition of genes encoding broad-spectrum β-lactamases, known as extended-spectrum β-lactamases, that confer resistance to broad-spectrum cephalosporins. Plasmid-mediated quinolone resistance genes (conferring resistance to quinolones) and mcr-1 genes (conferring resistance to colistin) also contribute to antimicrobial resistance. This study aimed to investigate the prevalence of antimicrobial susceptibility and to detect β-lactamase and colistin resistance genes of E. coli isolated from broiler farms in Egypt. MATERIALS AND METHODS: Samples from 938 broiler farms were bacteriologically examined for E. coli isolation. The antimicrobial resistance profile was evaluated using disk diffusion, and several resistance genes were investigated through polymerase chain reaction amplification. RESULTS: Escherichia coli was isolated and identified from 675/938 farms (72%) from the pooled internal organs (liver, heart, lung, spleen, and yolk) of broilers. Escherichia coli isolates from the most recent 3 years (2018–2020) were serotyped into 13 serotypes; the most prevalent serotype was O125 (n = 8). The highest phenotypic antibiotic resistance profiles during this period were against ampicillin, penicillin, tetracycline, and nalidixic acid. Escherichia coli was sensitive to clinically relevant antibiotics. Twenty-eight selected isolates from the most recent 3 years (2018–2020) were found to have MDR, where the prevalence of the antibiotic resistance genes ctx, tem, and shv was 46% and that of mcr-1 was 64%. Integrons were found in 93% of the isolates. CONCLUSION: The study showed a high prevalence of E. coli infection in broiler farms associated with MDR, which has a high public health significance because of its zoonotic relevance. These results strengthen the application of continuous surveillance programs.