Genomic and phylogenetic characterization of human-adapted methicillin-resistant Staphylococcus aureus clonal complex...

This study investigated the molecular epidemiology, genomic characteristics, and phylogenetic relationships of methicillin-resistant Staphylococcus aureus (MRSA) clonal complex 398 (CC398) isolates recovered from clinical infections in Taiwan. Fourteen CC398 MRSA isolates were identified between 2018 and 2022 from patients with skin and soft tissue infections and bloodstream infections at two regional hospitals. Whole-genome sequencing (WGS), core genome multilocus sequence typing, and comparative genomic analyzes revealed two distinct lineages: 10 sequence type (ST) 1232 and 4 ST398 isolates. Both ST1232 and ST398 carried SCCmec V; ST1232 carried SCCmec V(5C2), Panton-Valentine leukocidin (PVL), immune evasion cluster (IEC), and a radC::Tn554 insertion. These isolates showed high genomic similarity to human-adapted CC398 strains from Japan and Korea. In contrast, ST398 isolates lacked PVL and Tn554 but retained IEC genes, showing greater SCCmec diversity. None of the patients had livestock exposure, indicating possible community transmission. These findings highlight ST1232 as a clonally expanding, human-adapted MRSA lineage in Taiwan with distinct genetic traits and phylogenetic clustering with international isolates. Continued genomic surveillance is warranted to track its dissemination and guide infection control efforts.

This study reveals two human-adapted methicillin-resistant Staphylococcus aureus (MRSA) CC398 lineages in Taiwan: ST1232 and ST398. ST1232 carried Panton-Valentine leukocidin, immune evasion cluster (IEC), and radC::Tn554, while ST398 retained IEC and exhibited SCCmec variability. These findings highlight the public health importance of monitoring emerging MRSA lineages.