Searching for Bacterial Pathogens in Pediatric Patients with Chronic Recurrent Multifocal Osteomyelitis Using 16S rRNA Quantitative Real-Time PCR

BACKGROUND: Chronic recurrent multifocal osteomyelitis (CRMO) is a rare auto-inflammatory disease in children that causes relapsing episodes of pain. Patients are treated with anti-inflammatory medications or immune-modulating agents. Increasing evidence suggests that CRMO is mediated by dysregulation of the interleukin-1 pathway, not a bacterial source. However, CRMO is often a diagnosis of exclusion, and patients occasionally receive antimicrobials for possible culture negative infectious osteomyelitis. Few prior studies have utilized molecular diagnostic techniques to identify bacterial pathogens in CRMO bone biopsies. METHODS: Musculoskeletal specimens sent for culture during routine clinical care were banked from patients admitted to Children’s Hospital Colorado from 6/2012 to 10/2016. On retrospective chart review, 28 specimens were collected from 16 patients ultimately diagnosed with CRMO. Specimens were processed and extracted prior to molecular testing. All samples underwent quantitative real-time PCR (qPCR) testing using bacterial load assays targeting the bacterial 16S rRNA gene. RESULTS: Mean age at time of sample collection was 9.2 years. CRMO diagnosis was made by clinical, pathologic, and radiographic findings. All patients had pathology findings consistent with CRMO including lymphoplasmacytic infiltrate, focal necrosis, and/or marrow fibrosis. All patients had MRI findings consistent with CRMO. No patient had bacteria identified on Gram stain; 2/28 samples (7%) had bacterial growth on culture (both were coagulase-negative staphylococcus, felt to be contaminant). None of the 28 specimens met the threshold of bacterial load on qPCR testing to necessitate bacterial sequencing. None of the 16 patients were treated with antimicrobials and there were no readmissions for clinical worsening. CONCLUSION: CRMO patients did not have bacteria identified on universal bacterial 16S rRNA testing. This finding further supports that CRMO patients do not require antimicrobial therapy. Future steps to exclude infectious pathogens in CRMO could include next-generation DNA sequencing. DISCLOSURES: All authors: No reported disclosures.