Increased Oxacillin Resistance in Thigh Pyomyositis in Diabetic Patients

Thigh abscesses due to pyomyositis are uncommon. To guide empiric antibiotic therapy in diabetics we determined the rate of such infections due to oxacillin-resistant Staphylococcus aureus and Gram-negative organism infections, and whether the occurrence of oxacillin-resistant pathogens increased during the study period. We retrospectively reviewed 39 adult patients with diabetes mellitus treated for a deep thigh abscess. There were 29 men and 10 women; their mean age was 45 years. Comorbidities were present in 15 patients. S. aureus was the most common pathogen, present in 82% (32/39) of our patients. Gram-negative organisms were cultured in 14% (6/39) of patients and anaerobes in 10% (4/39). The infection was polymicrobial in 12 of 39 patients (31%). Oxacillin-resistant S. aureus comprised 25% (8/32) of infections due to S. aureus. Oxacillin-resistance increased during the last 3 years of this study from one of 18 S. aureus isolates from 1994 to 2004 to seven of 14 isolates from 2004 to 2006. In diabetic patients with thigh pyomyositis, empiric antibiotic therapy should provide broad spectrum coverage for oxacillin-resistant S. aureus, Gram-negative, as well as anaerobic organisms.