Background/Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) is a major causative pathogen in Republic of Korea. While numerous variants exist, the long-term evolutionary history of indigenous lineages remains unclear. Therefore, this study aimed to reconstruct the high-resolution population structure of Korean MRSA. Methods: A total of 191 MRSA clinical isolates collected between 1999 and 2025 were obtained from four Korean biobanks. Whole-genome sequencing was conducted and international MRSA genomes from the National Center for Bioinformatics were used as a control group. A genome-wide association study, including single-nucleotide polymorphism (SNP)-based phylogenomic analysis, principal component analysis (PCA), and ADMIXTURE, was performed for distribution analysis. A time-scale epidemiological analysis was conducted using SNP-based phylogenetic data. Additional profiling was performed via core genome multilocus sequence typing (cgMLST) for comparison with the SNP-based phylogenomic results. Finally, antimicrobial resistance and virulence factor genes were annotated using the ResFinder and VirulenceFinder databases. Results: Phylogenetic analysis identified five major clades: 1 (ST5), 2 (ST6), 3 (ST72), 4 (ST1/ST188), and 5 (ST8/ST239/ST254). Time-scaled analysis estimated that these major clades began to diverge in the early 20th century (e.g., Clade 1 around 1918). Notably, Korean ST5 isolates formed a sublineage distinct from North American strains, characterized by unique AMR profiles and divergence in the 1960s. ST72 formed an independent clade that was phylogenetically closer to clade 4 (ST1/ST188) than to the canonical CC8 group (clade 5). Furthermore, the ST1 isolates showed a temporal split into an older lineage and a recent sublineage, with expanded AMR pro-files. Conclusions: By integrating time-scale phylogenetics with cgMLST, we elucidated the evolutionary history and transmission dynamics of Korean MRSA.

The genome of Coxiella burnetii KZQ2, isolated from clinical patients in Korea, is 2.04 MB long. Multispacer types were ST77, and phylogenetic tree analysis showed that KZQ2 is closely related to the CbuK_Q154 chronic strain isolated from human endocarditis patients in the USA.

In South Korea, studies on methicillin-resistant Staphylococcus aureus (MRSA) have predominantly focused on molecular typing, with ST5 and ST72 consistently identified as dominant lineages. However, data on the distribution of virulence factors and antimicrobial resistance genes among recent clinical MRSA isolates remain limited. This study aimed to characterize antimicrobial resistance determinants and virulence gene profiles in contemporary clinical MRSA isolates from South Korea. One hundred human-derived clinical MRSA isolates, collected between February 2024 and January 2025 from the Antibiotic Resistance Specialized Pathogen Resource Bank of Hallym University Sacred Heart Hospital (Anyang-si, Republic of Korea), were analyzed. The isolates were evaluated for antimicrobial susceptibility and molecular characterization including multilocus sequence typing (MLST), staphylococcal cassette chromosome mec typing, accessory gene regulator grouping, staphylococcal protein A typing, and profiling of virulence and antimicrobial resistance genes. Genetic relatedness among isolates was also assessed. The isolates demonstrated high resistance rates to penicillins, cephalosporins, fluoroquinolones, macrolides, lincosamides, and tetracyclines, whereas most remained susceptible to vancomycin, linezolid, nitrofurantoin, and trimethoprim-sulfamethoxazole. Amino acid substitutions in antimicrobial resistance-associated genes were identified in 74% of isolates, with the greatest diversity observed among ST5 strains. MLST analysis revealed that ST5 isolates harbored a broader spectrum of resistance determinants, while ST72 isolates exhibited a more limited resistance profile. PFGE identified three major clone clusters, each associated with distinct superantigen gene profile. Panton-Valentine leukocidin genes were detected exclusively in ST8 and ST22 isolates, whereas the arginine catabolic mobile element was found only in ST8 isolates. Contemporary MRSA isolates in South Korea tested in this study share a conserved core virulence repertoire but display lineage-specific differences in resistance and virulence determinants. These findings enhance comparative molecular characterization of MRSA in South Korea and underscore the need for continued surveillance to elucidate lineage evolution and transmission dynamics.