1651. Utility of Staphylococcus aureus Nares Screening in Hospitalized Children with Osteomyelitis

BACKGROUND: Antibiotics with activity against methicillin-resistant Staphylococcus aureus (MRSA) are frequently started empirically in children diagnosed with osteomyelitis. At our institution clinicians increasingly obtain at time of admission a PCR-based staphylococcal nares screen (SNS) which can differentiate methicillin-sensitive Staphylococcus aureus (MSSA) and MRSA. We aimed to evaluate the utility of SNS for antibiotic optimization in pediatric inpatients with osteomyelitis. METHODS: A retrospective chart review was conducted of children (< 20 years) admitted for osteomyelitis (January 01, 2021 to December 31, 2022) who had a SNS and a clinical culture (i.e. site of infection or blood) performed as part of their diagnostic work up. RESULTS: A total of 36 children were included, median age (range) of 8.5 years (0-19). Etiologic diagnosis was established in 52.8% (n=19), most infections were with MSSA (n=12), followed by MRSA (n=4), and MRSA/MSSA (n=1). The prevalence of nasal MRSA and MSSA colonization was 8.3% (n=3) and 47.2% (n=17), respectively. The sensitivity (SE), specificity (SP), positive predictive value (PPV) and negative predictive values (NPV) of the SNS test to predict a MRSA and a MSSA infection were 40.0%, 96.8%, 66.7%, 90.9%, and 75.0%, 66.7%, 52.9%, 84.2%, respectively. When including only patients with site specific cultures (n=25), SE, SP, PPV and NPV of the SNS test to predict MRSA and MSSA infection were 40%, 100%, 100%, 86.9%, and 70%, 60%, 53.8%, 75.0%, respectively. Of those whose SNS test was negative (n=16), infection with MSSA was found in some (n=3) but none had documented MRSA infection. In about half (15/32, 46.9%) anti-MRSA therapy was discontinued during the hospitalization, de-escalation solely in response to a negative MRSA SNS occurred in some (n=3, 20.0%). CONCLUSION: We found that children with osteomyelitis have a disproportionate high rate of nasal colonization with MSSA which was also the primary etiologic cause for the infection in this cohort. The SNS was noted to show a high NPV for MRSA infection which may help encourage clinicians to de-escalate potentially toxic anti-MRSA therapy in a timely fashion, especially in non-critical patients. Further prospective study is warranted. DISCLOSURES: All Authors: No reported disclosures