Genomic analysis of ocular Staphylococcus aureus reveals emerging lineages, sequence type- and region-associated virulence gene profiles, and distinctions from non-ocular strains

Ocular infections remain a major cause of visual morbidity worldwide. Staphylococcus aureus is one of the most common causative pathogens, in which bacterial virulence contributes to tissue damage and chronic or recurrent infection. This study aims to define the population structure, regional variation and potential virulence strategies of ocular S. aureus globally.

Whole-genome sequencing data from 220 S. aureus isolates obtained from patients with ocular infections were analysed to assess lineage-, region-, niche-traits, and virulence gene repertoires. An additional 295 non-ocular isolates were included for comparative analysis to identify virulence features associated with ocular infection.

Four sequence types (ST5, ST8, ST30, and ST22) predominated, with the emergence of PVL-positive ST22 in Asia. Virulence gene prevalence varied across continents, with enrichment of multiple genes in North American and Asian isolates, reduced prevalence of 2 genes in European isolates, and South American, Oceanian and African isolates comparable to global levels. Compared with non-ocular isolates, ocular strains had significantly higher carriage of the type 8 capsular polysaccharide locus cap8HIJK (40.45-41.36% vs. 27.12-28.17%, adjusted p < 0.05) and the biofilm-associated genes icaR (100% vs. 95%, adjusted p = 0.0281) and sdrC (adjusted p = 0.038). In contrast, ocular isolates were less likely to carry the classical cytotoxins (hla, hlb) or matrix-binding adhesin (clfA).

This global genomic analysis reveals lineage-, region-, and niche-specific virulence patterns in ocular S. aureus. Ocular isolates preferentially exhibit traits associated with persistence and immune evasion rather than invasive tissue damage, highlighting potential targets for improved prevention and management.