Association of Prior Antibiotic Use With Negative Surgical Bone Biopsy Cultures and Disease Recurrence in Diabetes-related Foot Osteomyelitis

OBJECTIVE: The authors hypothesized that prior antibiotic treatment does not reduce culture positivity and that empirical antibiotic therapy in culture-negative cases does not increase the risk of amputation or recurrence in diabetes-related foot osteomyelitis (DFO). METHODS: This retrospective study included 100 consecutive patients with DFO treated at La Paloma Hospital, Diabetic Foot Unit, in Las Palmas de Gran Canaria, Spain, from June 1, 2010, to December 1, 2016. Surgical bone biopsies were obtained for microbiological and histologic analysis. Patients were followed for at least 1 year post-wound healing to monitor infection recurrence. Chi-squared and Fisher exact tests were used to analyze associations between antibiotic use, culture results, amputation, and recurrence. RESULTS: Cultures were negative in 28% of cases. No association was found between prior antibiotic use and negative cultures ( P =.443). Amputation rates were similar in patients with positive (31.9%) and negative cultures (32.1%, P =.98). Infection recurrence occurred in 23% of patients, with no significant difference between positive (26.4%) and negative cultures (14.3%, P =.19). Post hoc power analysis showed 79% power to detect differences in infection recurrence. CONCLUSIONS: Prior antibiotic use did not significantly impact culture positivity in DFO. Empirical antibiotic therapy in culture-negative cases did not increase the risk of amputation or recurrence. Treatment decisions should be individualized, adhering to antimicrobial stewardship principles. Further studies are needed to clarify the relationship between antibiotic exposure, culture results, and outcomes in DFO.