Diabetic foot infections are associated with substantial morbidity and mortality . Important risk factors for development of diabetic foot infections include neuropathy, peripheral vascular disease, and poor glycemic control. In the setting of sensory neuropathy, there is diminished perception of pain and temperature; thus, many patients are slow to recognize the presence of an injury to their feet. Autonomic neuropathy can cause diminished sweat secretion resulting in dry, cracked skin that facilitates the entry of microorganisms to the deeper skin structures. In addition, motor neuropathy can lead to foot deformities, which lead to pressure-induced soft tissue damage. Peripheral artery disease can impair blood flow necessary for healing of ulcers and infections. Hyperglycemia impairs neutrophil function and reduces host defenses. Trauma in patients with one or more of these risk factors precipitates development of wounds that can be slow to heal and predispose to secondary infection.
The microbiology, clinical evaluation, diagnosis, and management of diabetic foot infections will be reviewed here. The general evaluation of the diabetic foot and management of uninfected diabetic foot lesions are discussed separately. (See "Evaluation of the diabetic foot" and "Management of diabetic foot lesions".)
OVERVIEW OF APPROACH TO THE PATIENT
In 2012, the Infectious Disease Society of America updated guidelines on the diagnosis and management of diabetic foot infections, which were originally published in 2004 . Practical guidelines are also published regularly by the International Working Group on the Diabetic Foot . The information reviewed in this topic is largely consistent with these guidelines.
The evaluation of a patient with a diabetic foot infection involves three key steps: 1) determining the extent and severity of infection, 2) identifying underlying factors that predispose to and promote infection, and 3) assessing the microbial etiology.
The clinical history should focus on the details related to recent trauma, the duration of the current lesion(s), associated systemic symptoms, and prior treatment, if any. Mechanical factors that may predispose to the formation of an ulcer should be noted, and the history of blood glucose control should be assessed. Evidence of systemic toxicity should also be carefully noted.