393. Changing Trends, Risk Factors, and Treatment Challenges in Staphylococcus aureus Septic Arthritis

BACKGROUND: Staphylococcus aureus is a common organism in native septic arthritis. It is traditionally believed to be self-limited with rapid and aggressive debridement and appropriate antibiotic selection. The incidence of S. aureus septic arthritis is increasing, and further characterization is needed to improve diagnosis and treatment. For patients presenting with native S. aureus septic arthritis, we evaluated the reliability of methicillin-resistant S. aureus (MRSA) screening as a predictor to rule out MRSA septic arthritis, the risk factors associated with this disease, and the treatment and surgical outcomes. METHODS: A retrospective case–control study of patients diagnosed with septic arthritis in the UPMC health system (Pittsburgh, PA) between 2012 and 2016 was completed. The primary outcomes of interest were surgical intervention and the need to alter antibiotic treatment. Patient demographics, characteristics, and outcomes were recorded. RESULTS: A total of 215 cases of septic arthritis were identified, and 64% (n = 138) had S. aureus cultured. In this set, 36% (50/138) of these patients were identified with MRSA. Of the patients diagnosed with MRSA septic arthritis, 50% screened prior to admission had a positive result (8/16) and 48% screened during admission had a positive result (14/29). Compared with septic arthritis with other organisms, risk factors associated with S. aureus included history of intravenous drug use (OR: 4.3, CI: 1.7 to 10.8, P = 0.002) and being immunocompetent (OR: 0.3, CI: 0.1 to 0.6, P = 0.002). These infections were associated with concurrent infections of the spine (OR: 5.7, CI: 2.1 to 15.1, P = 0.0005). As compared with other organisms, there was a high probability of switching antibiotics during treatment (OR: 3.7, CI: 1.1 to 13.0, P = 0.04) and relapse of infection (OR: 4.2, CI: 1.2 to 14.6, P = 0.02). CONCLUSION: S. aureus septic arthritis is associated with intravenous drug use, and not with immunosuppression. A negative MRSA screen does not rule out this organism. Concurrent spine infections are common. There is a high likelihood of infection relapse and that antibiotics will need to be altered during treatment. With the opioid epidemic, the incidence is likely to increase further. More work is needed to improve diagnosis and overcome treatment challenges. DISCLOSURES: All authors: No reported disclosures.