Methicillin-sensitive Staphylococcus aureus lineages contribute towards poor patient outcomes in orthopaedic device-related infections

Staphylococci are the most common cause of orthopaedic device-related infections (ODRIs), with Staphylococcus aureus responsible for a third or more of cases. This prospective clinical and laboratory study investigated the association of genomic and phenotypic variation with treatment outcomes in ODRI isolates. Eighty-six invasive S. aureus isolates were collected from patients with ODRI, and clinical outcome was assessed after a follow-up examination of 24 months. Each patient was then considered to have been "cured" or "not cured" based on predefined clinical criteria. Whole genome sequencing and molecular characterisation identified isolates belonging to globally circulating community- and hospital-acquired lineages. Most isolates were phenotypically susceptible to methicillin and lacked the SCCmec cassette (MSSA; 94%), but contained several virulence genes, including toxins and biofilm genes. While recognising the role of the host immune response, we identified genetic variance which could be associated with the infection severity or clinical outcome. While this and several other studies reinforce the role antibiotic resistance (e.g., MRSA infection) has on treatment failure, it is important not to overlook MSSA that can cause equally destructive infections and lead to poor patient outcomes.