Prevalence, Antimicrobial Resistance Profile, and Genetic Characteristics of Methicillin-Resistant Isolated from Retail Raw Fish in South Korea.

Given the limited genetic characterization of methicillin-resistant (MRSA) in South Korea, we performed whole-genome sequencing (WGS) on eight MRSA strains isolated from raw fish products, including 327 sliced raw flatfish, 111 flatfish stew products, 85 sliced raw rockfish, and 11 rockfish stew products. Phylogenetic analysis revealed two distinct clusters-comprising five ST72-t324-SCCIVc strains and two novel sequence types-as well as a singleton strain (ST630-t4549-SCCV). A total of five antimicrobial resistance genes (ARGs), four plasmid replicon genes, three mobile genetic element genes, and seventy-three virulence factor genes were identified, with distinct genetic profiles observed between the clusters. Notably, several MRSA strains were isolated from samples obtained at the same retail market, indicating potential local clustering. Four ST72-t324-SCCIVc strains, collected from the same market, shared identical profiles in terms of four ARGs, two plasmid replicons, two mobile genetic elements, and several virulence factor genes. These findings provide valuable insights into the genomic characteristics of MRSA in raw fish products and highlight the need for ongoing surveillance and monitoring efforts in South Korea.