The fetid foot: lower-extremity infections in patients with diabetes mellitus

Infections of the lower extremities in patients with diabetes mellitus have been attributed to Staphylococcus aureus and other facultatively anaerobic bacteria. However, a review of 30 consecutive diabetics who required surgery for lower-extremity infections revealed that 17 had mixed infections due to both obligate and facultative anaerobes; only six had infections due to S. aureus. Mixed infections often had characteristics of anaerobic suppuration and responded poorly to therapy. Patients with mixed infections required more operations than did those with staphylococcal infections, and their surgical wounds healed more slowly. Seven patients had infections with mixed enteric bacteria (neither anaerobes nor S. aureus), and their response to therapy was intermediate between that of the patients with mixed anaerobic infections and those with staphylococcal infections. Nine additional patients with mixed anaerobic infections were treated with cefoxitin; three required amputations at a level above the ankle, but six patients improved and required only limited surgery that preserved foot function. Bacteroides fragilis was the anaerobe isolated most often. Cefoxitin (less than or equal to 20 micrograms/ml) inhibited all of the anaerobes isolated from the nine patients and 97% of an additional 135 consecutive clinical isolates of B. fragilis; 98% of 54 strains of Bacteroides oralis and all of 34 strains of Bacteroides melaninogenicus were also inhibited. These in vitro results and the results of our clinical study show that cefoxitin is a promising antibiotic for therapy of foot infections due to a mixed flora of anaerobes in diabetics.