Diabetic foot infections. Bacteriology and activity of 10 oral antimicrobial agents against bacteria isolated from consecutive cases

OBJECTIVE - To study the relative frequency of bacterial isolates cultured from community-acquired foot infections and assess their comparative in vitro susceptibility to sparfloxacin, levofloxacin, and eight other commonly used oral antimicrobial agents. RESEARCH DESIGN AND METHODS - This is a prospective study in which the infected wounds of 25 consecutive diabetic patients seen by one of the authors were cultured as they entered the hospital. Isolates were stored and tested for susceptibility to 10 oral antimicrobial agents using the agar dilution method. RESULTS - Staphylococcus aureus was the most common isolate (76% of patients), including methicillin-resistant S. aureus (MRSA) in 5 of 25 (20%) patient wounds. Streptococci, enterococci, Enterobacteriaceae, and anaerobes were also present in greater than or equal to 40% of patient wounds. Sparfloxacin and levofloxacin were the most active agents tested with activity against greater than or equal to 88% of isolates. Isolates resistant to sparfloxacin and levofloxacin included MRSA, enterococci, and some anaerobes. When analyzed by prior exposure to antibiotics, patients who had previously received oral antibiotics were more likely to have MRSA, enterococci, and Pseudomonas aeruginosa isolated and less likely to have Enterobacteriaceae and anaerobes isolated from their wounds. CONCLUSIONS - MRSA and enterococci are now a common cause of diabetic food infections, and the increased prevalence may be due to antimicrobial use. These wounds may require use of combined antimicrobial therapy for initial outpatient management. The new fluoroquinolones, sparfloxacin and levofloxacin, were the most active oral agents tested.