Treatment of Uncomplicated Skin and Skin Structure Infections in the Diabetic Patient

Diabetic neuropathy can lead to the development of ulcers on the lower extremities. Prompt treatment lowers the likelihood of infection and reduces the probability that an established infection will lead to amputation. Antibiotics are selected on the basis of the suspected organism and the level of infection. Unnecessary antibiotic prophylaxis is discouraged because it increases the likelihood that bacterial resistance to the antibiotic agent will develop. Culture samples must be taken by curettage of biopsy rather than by swabbing to assure detection of pathogens.

Introduction

In the United States, foot infection is the leading cause of both diabetes-related hospitalization (1) and lower-extremity amputation. (2-4) More than 90% of cases of osteomyelitis of the foot are associated with infected foot ulcers. The American Diabetes Association estimates that almost 90,000 lower extremity amputations secondary to diabetes are performed each year. In 85% of amputations, ulceration is a pre-disposing factor. The 5-year survival rate of unilateral diabetic amputees is 50%; for bilateral amputees, the rate drops to 0%.
Lower-extremity neuropathy associated with diabetes mellitus often leads to the development of uncomplicated skin and skin structure infections (uSSSIs) (Figure 1). Untreated, uSSSIs may develop into complicated infections (Figure 2). Long-term survival of diabetic patients depends on the recognition and proper treatment of uSSSIs before they develop into more serious conditions that warrant amputation. This article focuses on the treatment of uSSSIs in diabetic patients.

Classifying the Diabetic Wound
Proper classification of the diabetic wound is essential before selecting treatment. Diabetic foot infections are divided into 4 categories of severity: non-infected, mild, moderate, and severe. (5)
Non-infected ulcers are characterized by granulation of the tissue base, shallow tract, the absence of cellulitis and pus, and normal serous drainage. The wound is likely to be contaminated or colonized by bacteria but there are no signs of infection.

Mildly infected ulcers have 2 or more manifestations of inflammation (purulence, erythema, tenderness, pain, induration, warmth) and cellulitis or erythema that extends 2 cm or less around the ulcer. The infection is restricted to skin and superficial subcutaneous tissues. This type of wound is usually local and patients have no systemic illness or other complications.

Moderately infected ulcers have one or more of the following characteristics: cellulitis greater than 2 cm; lymphangitic streaking, location beneath superficial fascia; gangrene; abscess of deep tissue; and muscle, tendon, bone, or joint involvement. The patient is metabolically stable and systemically well, although white blood cell counts or glucose levels may change and require treatment. If located in the foot or limb, wounds of this type may eventually lead to amputation.

Severely infected ulcers have the characteristics of moderate infection plus one or more additional factors--signs or symptoms of sepsis, significant metabolic imbalance, severe peripheral vascular disease, or combinations of these. Severe diabetic infections are life-threatening. In diabetic patients, uSSSIs comprise only non-infected and mildly infected wounds.