# Genomic and phylogenetic characterization of human-adapted methicillin-resistant Staphylococcus aureus clonal complex 398 lineages in Taiwan

## TL;DR

This study identifies two human-adapted MRSA lineages in Taiwan, highlighting their genetic traits and potential for community transmission.

## Contribution

The study characterizes two distinct CC398 MRSA lineages in Taiwan with unique genomic features and international phylogenetic links.

## Key findings

- ST1232 MRSA isolates carry SCCmec V(5C2), PVL, IEC, and radC::Tn554 insertion.
- ST398 isolates lack PVL and Tn554 but retain IEC and show SCCmec diversity.
- Both lineages are genetically similar to human-adapted CC398 strains from Japan and Korea.

## Abstract

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.