Methicillin-resistant Staphylococcus aureus:: an increasing problem in a diabetic foot clinic

Aim To study the prevalence of pathogenic organisms and the prevalence and outcome of methicillin-resistant Staphylococcus aureus (MRSA) infection in foot ulcers in diabetic patients. Methods A retrospective analysis of wound swabs taken from infected foot ulcers in diabetic patients, selected from an outpatient diabetic foot clinic. Seventy-five patients (79 ulcers) with positive wound swabs were included. Size of ulcer and time to healing, in particular for MRSA-infected ulcers, were measured in all patients. Results Gram-positive aerobic bacteria were the commonest micro-organism isolated (56.7%) followed by Gram-negative aerobic bacteria and anaerobes (29.8% and 13.5%, respectively). Of the Gram-positive aerobes, S. aureus was found most frequently and 40% were MRSA. MRSA was isolated more commonly in patients treated with antibiotics prior to the swab compared to those who had not received antibiotics (P=0.01). Patients whose foot ulcers were infected by MRSA had longer healing time than patients whose ulcers were infected by methicillin-sensitive S. aureus (mean (range) 35.4 (19-64) and 17.8 (8-24) weeks, respectively, P=0.03). Conclusion MRSA infection is common in diabetic foot ulcers and is associated with previous antibiotic treatment and prolonged time to healing. Further studies are required to assess the need for antibiotics in treating foot ulcers in diabetes and to assess the optimum therapeutic approach to this problem.