Clinical and genomic characterization of Staphylococcus argenteus isolates from a tertiary hospital in Beijing.

BACKGROUND: Staphylococcus argenteus, an emerging member of the Staphylococcus aureus complex (SAC) linked to severe infections globally, remains understudied in temperate regions such as northern China. METHODS: In this single-center retrospective study, we re-identified 2,080 clinical isolates, which were initially classified as S. aureus using conventional phenotypic methods at a tertiary hospital in Beijing, China. Re-identification was performed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), followed by definitive confirmation of S. argenteus strains via rpoB and nonribosomal peptide synthetase (NRPS) gene sequencing and whole-genome sequencing (WGS). Phenotypic and genomic analyses were subsequently conducted, including the exploration of candidate MS spectral peaks, antimicrobial susceptibility testing (AST), in vitro biofilm formation capacity assessment, as well as resistome and virulome characteristics. RESULTS: A total of three S. argenteus strains (0.14%) were confirmed among the SAC isolates. Four distinct MALDI-TOF MS spectral peaks (3452.7, 5004.2, 5303.8, and 6903.2 Da) were identified that may serve as potential discriminatory markers for S. argenteus, warranting validation in larger, geographically diverse multicenter cohorts. A conserved core virulome (adhesins, hemolysins, and immune evasion factors) was detected across all strains; one isolate uniquely harbored Panton-Valentine leukocidin (PVL, lukS/F-PV) and enterotoxin genes (seg, sei). All three isolates were susceptible to oxacillin, yet they exhibited variable biofilm formation capacities; two isolates demonstrated strong biofilm production, which may warrant further investigation as a potential contributor to localized persistence, though this remains a hypothesis requiring dedicated clinical and functional validation. Notably, despite the presence of genotypic resistance determinants, no fluoroquinolone resistance phenotypes were detected via in vitro AST. CONCLUSION: Our findings provide preliminary insights into the pathogenic potential of S. argenteus in this specific clinical environment. Although our large-scale screening revealed a remarkably low prevalence of S. argenteus in this local cohort, the small number of positive isolates highlights the need for multicenter surveillance to better understand its clinical impact and generalizability.