Antimicrobial Resistance Profiles of Enterococcus faecium and Enterococcus faecalis Isolated from Food Animal Carcasses in South Korea, 2014–2023

Antimicrobial resistance in livestock products poses an important public health threat globally. This study aimed to evaluate the antimicrobial resistance profiles and trends of Enterococcus faecium and Enterococcus faecalis isolated from food animal carcass samples during 2014-2023 in South Korea. The obtained 1632 E. faecium and 3493 E. faecalis isolates from cattle, pig, and chicken carcasses at the national level were tested for antimicrobial susceptibility using broth microdilution. E. faecium and E. faecalis isolates from chickens showed higher resistance rates to most evaluated antimicrobials compared with cattle or pig strains. E. faecium isolated from chickens showed high levels of resistance to ciprofloxacin, erythromycin, and tetracycline by >50%. Likewise, over 40% of the E. faecalis isolates recovered from chickens exhibited resistance to these antimicrobials. Of note, very few or no enterococci isolates were resistant to ampicillin, gentamicin, linezolid, and vancomycin. Furthermore, notwithstanding fluctuations, enterococci strains showed an increasing resistance trend to some antimicrobials, including erythromycin and streptomycin. E. faecium exhibited significantly greater multidrug resistance (MDR) rates in chickens compared with cattle and pig isolates, while MDR E. faecalis was higher in pigs and chickens than in cattle isolates (p < 0.05). The main components of the resistance patterns were erythromycin, ciprofloxacin, or tetracycline. Moreover, MDR patterns in E. faecalis (23.4%) and E. faecium (17.8%) include five or more antimicrobials. The MDR enterococci contaminating carcasses during the slaughtering of food animals can be spread to humans through the food chain, posing a potential hazard to public health. Thus, judicious use of antimicrobials and proper sanitary measures are essential to mitigate the risk of transmission.