The Microbiology and Clinical Presentation of Acute Bacterial Arthritis in Houston Area Children <5 Years Old in the Era of Molecular Diagnostics.

Background: While Staphylococcus aureus is the most common pathogen causing acute bacterial arthritis (ABA), the microbiology is diverse, particularly in young children. Kingella kingae is a well-known pathogen of ABA and can be particularly difficult to identify. We examined the impact of molecular diagnostics on ABA in a historically methicillin-resistant S. aureus (MRSA) endemic region.

Methods: Cases of ABA in children ≤5 years old between 2015 and 2022 were reviewed. The clinical features of cases were compared by causative pathogen. Trends in utilization of molecular diagnostics and rates of pathogen identification were examined.

Results: One hundred sixty-two eligible subjects were identified with a median age of 1.4 years. A pathogen was identified in 76.5%. The most identified pathogen was S. aureus (31.4%) of which 25.5% were MRSA. The next most identified organism was K. kingae (22.8%) followed by Streptococcus pneumoniae (5.6%). During the study period, a temporal increase was observed in the use of molecular diagnostics peaking at 85.7% of cases (P < 0.001); this was associated with a temporal reduction in the proportion of cases without a pathogen identified. The majority of K. kingae and S. pneumoniae cases were only identified by polymerase chain reaction (PCR)-based methods. MRSA and S. pneumoniae cases were associated with the highest rates of orthopedic sequelae.

Conclusions: While S. aureus remains the principal etiology of ABA in young children, K. kingae and S. pneumoniae are significant pathogens. Pathogen identification is substantially enhanced using molecular diagnostic studies, particularly those capable of detecting K. kingae and S. pneumoniae.