Prevalence of hypervirulent Staphylococcus aureus CC22-t309 in Pediatric Osteomyelitis and Septic Arthritis in China

Staphylococcus aureus is the primary pathogen of pediatric osteomyelitis and septic arthritis, yet the genetic mechanism of its tropism for bone and joint tissues remains unclear. Here, we performed a systematical study integrating the clinical metadata, whole-genome sequencing, and antimicrobial susceptibility testing on 152 S. aureus collected in Shanghai, China, 2013-2025. A total of 55 isolates from pediatric osteomyelitis and/or septic arthritis (OM-SA) were collected, along with 97 isolates from other infections as controls. Pediatric OM-SA patients exhibited significantly elevated inflammatory factors, including white blood cell (WBC), C-reactive protein (CRP), procalcitonin (PCT), neutrophil percentage (N%), and erythrocyte sedimentation rate (ESR). Among OM-SA-associated isolates, CC22-t309 (23.6%), CC59-t437 (20.0%), and CC398-t034 (9.0%) were identified as the dominant clonal complexes. CC22-t309-related infections were closely linked to heightened systemic inflammation, particularly with higher CRP and ESR levels. Among OM-SA-related strains, CC22-t309 more frequently harbored a set of virulence factors, including Panton–Valentine leukocidin (pvl, 100%), collagen adhesin (cna, 84.6%), and fibronectin-binding protein A or B (fnbA/B, 100%), with carriage rates notably higher than those of other subtypes (pvl: 0%~63.6%; can: 0%~19.2%; fnbA/B: 0%~26.9%; p