Epidemiology, clinical and molecular characteristics of Staphylococcus argenteus isolates from a tertiary care hospital in Riyadh, Saudi Arabia.

BACKGROUND: Staphylococcus argenteus (S. argenteus) is a recently described member of the Staphylococcus aureus complex (SAC) that is increasingly associated with human infections worldwide. To date, data on its prevalence and genomic characteristics in Saudi Arabia have not been investigated. This study aimed to determine the prevalence of S. argenteus in a tertiary care setting and characterize its genomic features.

METHODS: Species identification and antimicrobial susceptibility testing were performed using the updated Bruker MALDI-TOF MS, BD Phoenix, and VITEK 2 systems as part of routine clinical microbiology diagnostics. Genome sequencing was conducted to define the genetic characteristics and assess phylogenetic relationships.

RESULTS: Eight S. argenteus isolates were identified among 400 SAC isolates collected between July and September 2025, showing 2% prevalence. The isolates were recovered from diverse clinical specimens and remained largely susceptible to common antibiotics. All isolates harbored blaZ and fusB genes on rep20-containing plasmids, conferring penicillin and fusidic acid resistance, respectively, and had the fosfomycin resistance gene fosB chromosomally located. All isolates carried immune evasion genes (sak and s cn) and lacked those encoding Panton-Valentine leukocidin (PVL) and toxic shock syndrome toxin (TSST-1). Phylogenetic analysis revealed high genetic diversity among the Saudi isolates, while still forming a distinct cluster within the global ST2250 population.

CONCLUSION: This study provides the first genomic insight into S. argenteus in Saudi Arabia and establishes a baseline for future surveillance to better define its regional epidemiology and clinical relevance.