A retrospective analysis of the microbiology of diabetic foot infections at a Scottish tertiary hospital

BACKGROUND: This study represents the first Scottish retrospective analysis of the microbiology of diabetic foot infections (DFIs). The aims were to compare the microbiological profile of DFIs treated at a Scottish tertiary hospital to that in the literature, gather data regarding antimicrobial resistance and investigate potential trends between the microbiological results and nature or site of the clinical sample taken and age or gender of the patients. METHODS: A retrospective analysis of wound microbiology results was performed, data were obtained from one multidisciplinary outpatient foot clinic during the 12 months of the year 2017. Seventy-three patients and 200 microbiological investigations were included. In cases of soft tissue infection, the deepest part of a cleansed and debrided wound was sampled. In cases of osteomyelitis a bone biopsy was obtained. Factors influencing the pattern of microbial growth or prevalence of Staphylococcus aureus were investigated. RESULTS: Of the 200 microbiological investigations, 62% were culture positive, of which 37.9% were polymicrobial and 62.1% monomicrobial. Among the monomicrobial results (n = 77), most were Gram positive isolates (96.1%) and the most frequently isolated bacteria was S. aureus (84.4%). No methicillin-resistant S. aureus was reported. The prevalence of S. aureus in DFIs was associated with increasing age (p = 0.021), but no evidence of association with gender, anatomical sample site or sample material was found. CONCLUSION: The microbiological profile of DFIs in Scotland resembles that reported elsewhere in the UK. In this context, Gram positive organisms, primarily S. aureus, are most frequently isolated from DFIs. The S. aureus isolates identified were largely susceptible to antibiotic therapy. An association between increasing patient age and the prevalence of S. aureus in DFIs was observed.