From IV to oral: clinical outcomes in Staphylococcus aureus osteomyelitis

Abstract

Outcomes for patients receiving oral antibiotics for Staphylococcus aureus (SA) osteomyelitis, including methicillin-resistant SA (MRSA), are poorly characterized. We evaluated outcomes in patients treated with partial oral therapy at a public safety-net hospital. We identified osteomyelitis cases among hospitalized adults where SA was isolated from microbiologic specimens from 6/30/2021–6/30/2024. Demographics and event dates were extracted via electronic query. Osteomyelitis diagnosis (first episode per anatomic site) was confirmed by chart review. Hardware presence, comorbidities, antibiotic usage, and outcomes were collected. Clinical failure was defined as either readmission due to therapy adverse effect or infection within 90 days post-discharge, or as loss to follow-up (LTFU). Using logistic regression, variables associated with clinical failure were identified. 248 individuals with SA (40.3% MRSA) osteomyelitis were identified, including patients with retained hardware (63.3%), recent substance use (36.7%), and housing instability (19.4%). Most individuals (97.1%) received initial intravenous (IV) therapy (median 11 days [IQR 5,17]). Patients with retained hardware (OR 1.50; CI 0.85–2.72) and bacteremia (OR 5.10; CI 2.85–9.27), were more likely to receive greater than two weeks of IV therapy; neither of which was associated with clinical failure. Fifty-two individuals (20.9%) required a change in antimicrobial therapy (alternative oral or IV agent). The majority (51/79, 64.5%) of clinical failures among 79 patients were attributed to loss to follow up. MRSA (OR 1.92; 95% CI, 1.04–3.55) and recent substance use disorder (OR 2.42; 95% CI, 1.25–4.70) were associated with clinical failure in the adjusted analysis. In a high-risk SA osteomyelitis population treated with partial oral antibiotics, the majority (169/248, 68.1%) were treated successfully. N/a. Not applicable