Antimicrobial Resistance Profiles and Molecular Characteristics of Extended-Spectrum β-Lactamase-Producing Escherichia coli Isolated from Healthy Cattle and Pigs in Korea.

Antimicrobial-resistant bacteria isolated from food animals pose a major health threat to the public on this planet. This study aimed to determine the susceptibility profiles of isolated from cattle and pig fecal samples and investigate the molecular characteristics of extended-spectrum β-lactamase (ESBL)-producing using gene identification, conjugation, and Southern blot approach. Overall 293 were recovered from cattle (120 isolates) and pigs (173 isolates) in 7 provinces of Korea during 2017-2018. Ampicillin, chloramphenicol, streptomycin, and sulfisoxazole resistance rates were the highest in pigs' isolates (>60%,  ≤ 0.001) compared to that in cattle (3-39%). Multidrug resistance (MDR) was higher in pig isolates (73%) than in cattle (31%), and the MDR profile usually includes streptomycin, sulfisoxazole, and tetracycline. Resistance to critically important antimicrobials such as ceftiofur, colistin, and ciprofloxacin was higher in weaners than those from finishers in pigs. The gene was detected in 13% of the pig isolates. Eight isolates from pigs and one isolate from cattle were identified as ESBL-producers and ESBL genes belonged to ( = 4), ( = 3), and ( = 2). Notably, the and genes were found to be carried together in an identical plasmid (IncHI2) in two isolates from finisher pigs. The -carrying isolates belonged to phylogenetic groups B1 ( = 4), B2 ( = 2), A ( = 2), and D ( = 1). The genes and non-β-lactam resistance traits were transferred to the J53 recipient from seven -positive strains isolated from pigs. The genes belonged to the IncI1α, IncFII, and IncHI2 plasmids and are also associated with the IS, IS, IS, and elements. These findings suggested the possibility of -carrying transmission to humans through direct contact with cattle and pigs or contamination of food products.