Molecular characterization of multidrug-resistant avian pathogenic Escherichia coli from broiler chickens in Korea

This study was conducted to determine the phenotypic and genotypic characteristics of multidrug-resistant (MDR) avian pathogenic Escherichia coli (APEC). A total of 54 MDR APEC were divided into 23 serotypes, and O78 (16.6%) was the most frequently observed. The MDR APEC carried beta-lactamase-encoding genes (38.9%), integrons (61.6%), plasmid-mediated quinolone-resistant genes (20.4%), tetracycline-resistant genes (79.6%), sulfonamide-resistant genes (40.7%), and chloramphenicol-resistant genes (18.5%). Phylogenetic group D (44.4%), which is associated with extraintestinal strains, was the most frequently observed, but all MDR APEC, including groups A, B1, and B2, carried one or more virulence genes. This study analyzed the phenotypic and genotypic characterization in MDR APEC isolated from broilers with colibacillosis in Korea. It is important to monitor the occurrence of resistance genes in APEC. These bacteria may pose serious therapeutic problems when treating sick broilers. The MDR strains carried by animals and birds can enter the human food chain through the consumption of meat or other animal or poultry products.