Foot infections in diabetic patients: the role of anaerobes.

The prevalence of anaerobic bacteria in cultures of specimens from foot infections in diabetic patients is dependent upon the method of obtaining the specimen, the care with which it is transported anaerobically, and the sophistication of the laboratory methods. The rate at which anaerobes are isolated with use of the best methods ranges from 74% to 95% of patients, but it is only 41% to 53% in clinical studies of patients with limb-threatening infection. The mean number of bacterial isolates from an infected foot ranges from 4.1 to 5.8, of which 1.2 to 2.6 isolates are anaerobic. Most anaerobic isolates are gram-positive, and Peptostreptococcus species are most common. Bacteroides species are the most common anaerobic gram-negative isolates. Treatment covering anaerobic bacteria is included in most empirical regimens, but the use of agents that are modestly active against anaerobic organisms (i.e., fluoroquinolones or trimethoprim-sulfamethoxazole) has also been successful. Surgical debridement and drainage are essential adjuncts to antimicrobial therapy and may assist in the control of anaerobic infection. Questions regarding management of such infections parallel those regarding management of polymicrobial intraabdominal infections, but to date, studies of the former have been much less sophisticated than those of the latter.