Risk Factors, Screening, and Treatment Challenges in Staphylococcus aureus Native Septic Arthritis

BACKGROUND: Staphylococcus aureus is the most common cause of native septic arthritis. Few studies have characterized this disease during the US opioid epidemic. The role of methicillin-resistant Staphylococcus aureus (MRSA) nasal screening in this disease has not been elucidated. We sought to identify risk factors and outcomes for S. aureus native septic arthritis and to evaluate MRSA screening in this disease. METHODS: A retrospective cohort study of native septic arthritis patients (2012–2016) was performed. Demographics, risk factors, and outcomes were compared between Staphylococcus aureus and other native septic arthritis infections. Sensitivity, specificity, and predictive values of MRSA screening were assessed. RESULTS: Two hundred fifteen cases of native septic arthritis were included. S. aureus was cultured in 64% (138/215). MRSA was cultured in 23% (50/215). S. aureus was associated with injection drug use (odds ratio [OR], 4.33; 95% CI, 1.74–10.81; P = .002) and switching antibiotics (OR, 3.92; 95% CI, 1.01–21.38; P = .032). For every 10-year increase in age, the odds of S. aureus decreased (OR, 0.72; 95% CI, 0.60–0.87; P = .001). For 1-unit increases in Charlson comorbidity index score, the odds of S. aureus decreased (OR, 0.82; 95% CI, 0.73–0.91; P = .0004). MRSA screening during admission demonstrated a sensitivity of 0.59, specificity of 0.96, positive predictive value of 0.85, and negative predictive value of 0.84 for MRSA native septic arthritis. CONCLUSIONS: The opioid epidemic may be contributing to a demographic shift in native septic arthritis to younger, healthier individuals. S. aureus native septic arthritis has unique risks, including injection drug use. MRSA screening may be useful to rule in MRSA native septic arthritis.