Genomic Characterization of a Rare Methicillin-Susceptible Staphylococcus aureus ST72 Isolate Co-Harboring Panton-Valentine Leukocidin and Toxic Shock Syndrome Toxin-1 Encoding Genes from Northern Vietnam.

Staphylococcus aureus (S. aureus) possesses a diverse repertoire of virulence determinants that enable it to cause pathologies that span from mild, superficial skin and soft tissue involvements to severe, life-threatening systemic infections. Among these, Panton-Valentine leucocidin and toxic shock syndrome toxin-1 are important toxins associated with severe clinical manifestations. However, the coexistence of their encoding genes (pvl and tst) within a single S. aureus isolate is uncommon. In this study, 112 clinical S. aureus isolates collected at a hospital in northern Vietnam were screened for pvl and tst by PCR. The pvl gene was identified in 88 isolates (78.57%), whereas tst was present in 12 isolates (10.71%). Only a single isolate carried both virulence markers. Whole-genome sequencing identified this isolate, designated SA14HG, as an ST72 methicillin-susceptible S. aureus (MSSA) strain carrying pvl, tst, multiple hemolysins, adhesion-associated genes, immune evasion determinants, and the complete icaADBC biofilm operon. Comparative genomic analysis demonstrated that SA14HG clustered within the global ST72 lineage and harbored a ΦSa2-like prophage carrying pvl together with a SaPI-like pathogenicity island encoding tst, Sect. 3, and sel. Despite its extensive virulence repertoire, the isolate contained a relatively limited resistome comprising genes associated with resistance to β-lactams, aminoglycosides, and fosfomycin. Collectively, these findings describe a rare pvl/tst co-positive ST72-MSSA strain recovered from a patient with severe purulent dermatitis and underscore the utility of whole-genome sequencing for identifying uncommon toxin-positive lineages. The study further highlights the contribution of mobile genetic elements to the ongoing evolution of community-associated S. aureus populations.