Patient Factors Associated With Methicillin-Resistant Staphylococcus aureus Septic Arthritis in Children

Staphylococcus aureus is the most common causative organism in pediatric septic arthritis, with methicillin-resistant Staphylococcus aureus (MRSA) being responsible for a significant portion of these infections. Early identification and initiation of proper treatment may improve outcomes by minimizing potential morbidity. The purpose of this study was to identify variables obtained on initial patient presentation associated with MRSA septic arthritis. Sixteen factors were retrospectively evaluated in 109 consecutive pediatric patients diagnosed with culture-confirmed septic arthritis. Graphical and logistical regression analyses were employed to determine factors independently predictive of MRSA septic arthritis. Twenty-seven (25%) patients had MRSA and 82 (75%) had non-MRSA septic arthritis. C-reactive protein of 13.7 mg/L or greater, duration of symptoms of 4 days or more, heart rate of 126 beats per minute or greater, and absolute neutrophil count of 8.72x103 cells/mu L or greater were associated with MRSA septic arthritis. Ultimately, 98% of patients with 1 or no risk factors had non-MRSA and 96% of patients with MRSA septic arthritis had 2 or more positive risk factors. Elevated C-reactive protein, duration of symptoms, heart rate, and absolute neutrophil count are predictive of MRSA infection in the setting of pediatric septic arthritis and can be obtained on initial evaluation. In patients for whom there is concern for MRSA infection, this may guide more expedient treatment, such as early initiation of contact precautions and appropriate antibiotic therapy before culture results become available.