Diabetic foot infections

The pathogenesis of diabetic foot infection stems from three key factors neuropathy, angiopathy, and immunopathy. Aerobic gram-positive cocci, such as S. aureus and P-hemolytic streptococci, are the predominant pathogens in acutely infected diabetic foot ulcers. However, chronically infected wounds are subject to polymicrobial infection and require treatment with broad-spectrum antibiotics. 

Foot ulcers and related infections are among the most common, severe, and costly complications of diabetes mellitus (DM). Fifteen percent of all patients with DM develop at least one foot ulcer, resulting in direct health care expenditures of approximately 9 billion annually in the United States.26,27 Diabetic foot ulcers and wounds are highly susceptible to infection. Related skin, soft tissue, and bone infections account for 25% of all diabetes-related hospitalizations.28 More than half of all nontraumatic lower extremity amputations (LEAs) performed each year in Western nations are linked to diabetic foot infection 80,000 LEAs are performed annually in the United States alone.29,30... 

Not all diabetic foot ulcers are infected. However, infection is often difficult to detect when perfusion and the inflammatory response are limited in the diabetic patient. The common signs and symptoms (i.e., pain, erythema, and edema) of infection may be absent.32 Still, the diagnosis of diabetic foot infection depends mostly on clinical evaluation. 

Spreading soft tissue infection and osteomyelitis are often the first complications that develop from diabetic foot infection. Some patients develop bacteremia and sepsis. 

TABLE 70-5. Clinical Classification of a Diabetic Foot Infection... 

The goals of therapy for diabetic foot infection are eradication of the infection and avoidance of soft tissue loss and amputation. 

The severity of a patient s infection, based on the PEDIS scale, guides the selection of empirical antimicrobial therapy. While most patients with grade 2 diabetic foot infections can be treated as outpatients with oral antimicrobial agents, all grade 4 and many grade 3 infections require hospitalization, stabilization of the patient, and broad-spectrum IV antibiotic therapy.31... 

Tigecycline is not currently approved for the treatment of diabetic foot infections. 

Lipsky BA, Berendt AR, Deery G, et al. Diagnosis and treatment of diabetic foot infections. Clin Infect Dis 2004 39 885-910. Livesley NJ, Chow AW. Pressure ulcers in elderly individuals. Clin Infect Dis 2002 35 1390-1396. 

There are three major types of diabetic foot infections deep abscesses, cellulitis of the dorsum, and mal perforans ulcers of the sole of the foot. Osteomyelitis may occur in 30% to 40% of infections. 

---