Longitudinal surveillance and molecular characterization of methicillin-resistant Staphylococcus aureus (MRSA) from livestock carcasses in South Korea: A 12-year nationwide study (2013-2024).

内容摘要

Methicillin-resistant Staphylococcus aureus (MRSA) is a critical zoonotic pathogen posing a significant threat to global public health. While livestock-associated MRSA (LA-MRSA) is well-documented, long-term nationwide surveillance integrating molecular epidemiology remains limited in South Korea. This study investigated the prevalence, antimicrobial resistance (AMR), and molecular characteristics of MRSA from beef, pork, chicken, and duck carcasses over a 12-year period (2013-2024). From 4201 S. aureus isolates across 98 slaughterhouses, MRSA was identified via mecA polymerase chain reaction and characterized using multi-locus sequence typing (MLST), spa, and SCCmec typing. The overall MRSA prevalence was 6.4%, peaking in pork carcasses (9.2%), followed by beef carcasses (5.1%) and chicken carcasses (4.8%). Longitudinal analysis revealed the stable persistence of LA-MRSA ST398 in pork and ST692 in chickens throughout the study period. Notably, while the unique ST541 has not been detected since 2020, ST72-SCCmecIV (the dominant CA-MRSA in Korea) was consistently identified across all carcasses, with newly emerging ST672 and ST8 in chickens and beef, respectively, within the last three years. Multidrug resistance (MDR) was significantly higher in LA-MRSA (ST398, ST541, ST692) than in community-associated (CA-MRSA). These findings demonstrate the stable colonization of LA-MRSA and the increasing diversification of MRSA lineages in the livestock cycle, highlighting that carcasses serve as a primary vehicle for the dissemination of diverse MRSA lineages. This necessitates integrated "One Health" surveillance and rigorous hygiene interventions at the slaughtering stage to safeguard the food supply chain from emerging zoonotic risks.