16S rRNA Bacterial Identification in Evaluation of Orthopedic Infections and its Limited Role in Antimicrobial Stewardship

Background: 16S bacterial identification is a molecular diagnostic test that can aid in the diagnosis and management of orthopedic infections. The study aims to describe the diagnostic value of 16S for orthopedic infections and whether results of 16S impact antibiotic de-escalation. Methods: This retrospective cohort study included all patient encounters with 16S performed for evaluation of orthopedic infections at 1 Midwest academic center over a 5-year prepandemic period. Qualitative descriptions of the clinical cases, antibiotics, and 16S results were evaluated. Results: Four hundred fifty-two episodes were included for analysis. Overall, 9.5% of 16S tests detected bacteria. The most common indication for testing was for evaluation of septic arthritis. For diagnosing infectious episodes, 16S had a sensitivity of 15.5%, a specificity of 98%, a positive predictive value of 90.7%, and a negative predictive value of 47.9%. Analysis of all episodes demonstrated antibiotic de-escalation from pre-16S to post-16S time points. However, antibiotics were continued for a large number of episodes with negative 16S when judged as infectious by the treating clinician. Conclusions: 16S bacterial identification aided in the diagnosis and treatment of only a minority of orthopedic infections and results did not serve as a useful tool for antimicrobial de-escalation.