Diabetic Foot Infections: Microbiology and Antibiotic Therapy

Abstract

Infections of the feet of patients with diabetes mellitus comprise a heterogeneous group of clinical conditions. Peripheral neuropathy is the most important predisposing factor. Also important in many patients are impaired circulation and poor glucose control. Staphylococcus aureus and the beta-hemolytic streptococci are the main pathogens. Gram-negatives and anaerobes assume a greater role in the presence of chronic ulcerations and severe peripheral vascular disease. Osteomyelitis is more likely when the ulceration can be probed to the bone and when the ulcer is long-standing. MRI is the best imaging modality for confirming a diagnosis of osteomyelitis. Culture of bone obtained in the absence of antibiotic therapy is helpful in determining the microbiology and hence the therapeutic regimen. Whether the therapy is given orally or intravenously should be determined by the microbiology, the extent of the infection, and the general condition of the patient. Adjunctive surgical therapies are essential to a successful outcome in patients with necrotic tissue, dead bone, or impaired circulation. Duration of antibiotic therapy can be as short as 7 days for patients with superficial soft tissue infections and as long as 3 or 4 months in selected patients with advanced osteomyelitis.