Retrospective study of outcomes of short versus long duration of antibiotic therapy for residual osteomyelitis in surgically resected diabetic foot infection.

Introduction: Optimal treatment duration for residual osteomyelitis (OM) post-amputation in diabetic foot infection (DFI) remains unclear, with resultant heterogeneity in prescribing noted in clinical practice. We aimed to identify a difference in outcomes of long duration of antibiotics (LD) with short duration (SD) in patients with culture-positive proximal bone specimen post-amputation.

Methods: In this single-centre retrospective cohort study (Melbourne, Australia), we analysed antibiotic duration of DFI patients requiring amputation with culture-positive proximal bone specimen over a 31 month period (January 2019-September 2021). Primary outcome was reamputation or debridement at the same and/or contiguous site of amputation at 6 months. Secondary outcomes were readmission to hospital and/or recommencement of antibiotics for DFI at the same and/or contiguous site at 6 months.

Results: Among 92 patients (83% male, median age 67 years), 26 received <4 weeks (SD) and 66 received ≥4 weeks (LD) antibiotic therapy. In the SD group, primary outcome occurred in 9 patients (35%) compared with 15 patients (23%) in the LD group (P = 0.246). Both secondary outcomes occurred in 12 patients (46%) in the SD group compared with 18 patients (27%) in the LD group (P = 0.086). Adjusted logistic regression analysis showed SD was not significantly associated with primary outcome [OR 1.12 (95% CI 0.38-3.31)] or secondary outcomes [OR 1.67 (95% CI 0.60-4.66)].

Conclusions: This single-centre experience did not demonstrate significant difference in outcomes between antibiotic duration of <4 weeks and ≥4 weeks in DFI patients with culture-positive proximal bone specimen post-amputation. These data provide background for larger international randomized control trials to establish optimal treatment duration.