Consistent Differences between Wound Culture and Osteoarticular Infection Staphylococcus aureus Susceptibilities and Institutional Antibiograms at a Children’s Hospital

BACKGROUND: Aggregate hospital and unit-based antibiograms guide empiric antibiotic decision making but may not best inform the microbiology of certain important presentations. In this analysis, Staphylococcus aureus (SA) susceptibilities specifically from wound specimens and in acute osteoarticular infections (OAI) were compared with available antibiograms at a freestanding children’s hospital. METHODS: Encounter, billing, and electronic microbiology surveillance data were utilized to identify SA wound cultures and acute OAI (osteomyelitis and septic arthritis) cases at Women and Children’s Hospital of Buffalo, from 2013 to 2016. OAI cases’ medical records were reviewed to ensure diagnostic accuracy. SA wound and OAI specific data were tabulated and compared with published institutional antibiograms. General pediatric locations were defined as community clinics, the emergency room, and general pediatric wards, with intensive-care and oncology units excluded. RESULTS: Significant discordance existed between general pediatrics SA susceptibilities in the aggregate antibiograms, with both wound cultures and OAI cases, for all 4 years: Figures 1 and 2. The proportion of SA that was methicillin-susceptible (MSSA) was consistently higher in wound specimens than in aggregate data (e.g., 63% vs. 53% in 2016; p≤ 0.01), and is increasing: 63% in 2015–16 vs. 53% in 2013–14, p ≤0.01. Clindamycin (clinda) susceptibility for all SA (MSSA + MRSA) was higher in wound cultures than aggregate data, 89% vs. 82% for 2013–2015 (p ≤ 0.01). For OAI cases, the proportion of MSSA was consistently ~20% higher than in aggregate data (2016: 79% vs. 53%, P = 0.05), and clinda susceptibility for all SA in this group appears to be decreasing: 83% in 2015–16 vs. 96% in 2013–14, P = 0.13. CONCLUSION: While our institutional antibiograms created uncertainty, a wound culture review indicated that clinda remains an appropriate empiric choice for community-onset skin and soft-tissue infections. Conversely, an OAI specific analysis revealed a predominance of MSSA and higher rates of clinda-resistant SA, leading us to reappraise the empiric use of clinda in this subset. Pediatric facilities should emphasize stratified, specimen and clinical-context specific—rather than aggregate—antibiograms, especially for SA. DISCLOSURES: All authors: No reported disclosures.