391. Septic Arthritis and Acute Hematogenous Osteomyelitis in Children: Disease-Specific Antibiogram and Implications for Treatment

BACKGROUND: Osteomyelitis and septic arthritis are common pediatric musculoskeletal infections with potential to cause significant morbidity. Empiric antibiotic selection is made prior to the availability of microbiologic data. The aim of this study was to compare the epidemiology of osteoarticular infections (OAI) to antibiotic regimens and local antibiograms. METHODS: A retrospective study was performed on patients aged 6 months to 18 years with a diagnosis of septic arthritis or acute hematogenous osteomyelitis in a large, free-standing children’s hospital between July 2012 and July 2017. Exclusion criteria were chronic osteomyelitis, prior trauma or surgery at the site, noninfectious arthritis, and Lyme arthritis. Data collected from the electronic medical record included demographics, initial and discharge antibiotic therapy, and microbiologic results. Data were compared with the local antibiogram during the same time period. RESULTS: A total of 207 patients were included: 66 patients <4 years (< 4Y) and 141 patients ≥4 years (≥4Y). Causative pathogens were identified in 70% of patients. Staphylococcus aureus comprised 55% of positive results in children < 4Y and 73% in children ≥4Y. Among S. aureus cultures, 70–76% were methicillin sensitive (MSSA). Overall clindamycin susceptibility was 97%, with all resistant strains detected in children ≥4Y with MSSA. This is strikingly different than the institutional antibiogram showing 79% overall clindamycin sensitivity in S. aureus [82% in MSSA, 72% in methicillin resistant (MRSA)]. Kingella kingae was exclusively identified in children <4Y (21% of positives), which was also the group with the highest rate of culture-negative infection (41%). Intravenous clindamycin alone was the most frequent initial antibiotic regimen, prescribed for 41% of all patients. Initial antibiotic regimens matched organism susceptibilities in 90% of MRSA and 100% of MSSA infections. CONCLUSION: Our study revealed high rates of clindamycin-susceptible S. aureus in older children and K. kingae and culture-negative infection in children < 4 years with OAI. Antibiotic susceptibilities differing from our institutional antibiogram suggest that disease-specific antibiograms will aid with empiric treatment decisions. DISCLOSURES: All authors: No reported disclosures.