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

Multidrug resistance (MDR) of has become an increasing concern in poultry farming worldwide. However, can accumulate resistance genes through gene transfer. The most problematic resistance mechanism in 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 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 isolated from broiler farms in Egypt. Samples from 938 broiler farms were bacteriologically examined for isolation. The antimicrobial resistance profile was evaluated using disk diffusion, and several resistance genes were investigated through polymerase chain reaction amplification. was isolated and identified from 675/938 farms (72%) from the pooled internal organs (liver, heart, lung, spleen, and yolk) of broilers. 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. 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 , , and was 46% and that of was 64%. Integrons were found in 93% of the isolates. The study showed a high prevalence of 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.