The microbiological profile of diabetic foot infections: historical trends and relationship with amputation

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Background Understanding the microbial composition of diabetic foot infections (DFIs) is required to deliver appropriate antimicrobial therapy and to establish prognosis. Objectives We aimed to evaluate historical trends in the microbiological profile of DFIs and to explore the relationship between antimicrobial resistance and the risk of amputation. Patients and methods This was a retrospective study of patients with DFI treated in a tertiary vascular surgery centre between 2014 and 2024. The prevalence of different DFI organisms and the percentage of patients with organisms exhibiting resistance to DFI first-line antibiotics were calculated. The relationship between resistance to first-line options and amputation was established. Results There were 1164 samples collected from 274 patients (215 males, 78.5%). Prevalence of Enterococcus faecalis (R2 = 0.49, P = 0.017) and Proteus mirabilis (R2 = 0.52, P = 0.029) increased during the study period. Developing resistance to a first-line penicillin-allergic (PA) option was associated with a lower amputation-free probability [hazard ratio (HR) = 1.56, 95% confidence interval [CI]: 1.01–2.43, P = 0.046] compared to patients who remained susceptible. This association was not statistically significant for those developing resistance to first-line non-penicillin-allergic options (HR = 1.51, 95% CI: 0.96–2.37, P = 0.078). Conclusions Presence of organisms resistant to PA antibiotics is associated with a higher risk of amputation in a South-West London DFI population. This study highlights a rise in resistance to first-line antibiotics used in PA patients, underscoring the need for continuous surveillance of DFI microbiology resistance patterns to guide empirical therapy.