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A systematic search of the medical literature was performed in January, 2008. The search, limited to human subjects and English language journals, included MEDLINE®, PubMed, the Cochrane Database of Systematic Reviews, and UpToDate®. The current Infectious Disease Society of America practice guidelines for management of skin and soft tissue infections and those for diabetic foot infections can be found at

The skin serves as a barrier between humans and their environment and therefore functions as a primary defense mechanism against infections. The skin consists of the following layers and structures: (1) the epidermis, the outermost nonvascular layer of the skin, (2) the dermis, the layer of skin directly beneath the epidermis which consists of connective tissue containing blood vessels and lymphatics, sensory nerve endings, sweat and sebaceous glands, hair follicles, and smooth-muscle fibers, and (3) the subcutaneous fat, a layer of loose connective tissue beneath the dermis which primarily consists of fat cells. Beneath the subcutaneous fat lies the fascia, which separates the skin from underlying muscle. Skin and soft tissue infections (SSTIs) may involve any or all layers of the skin, fascia, and muscle. They may also spread far from the initial site of infection and lead to more severe complications, such as endocarditis, sepsis, or streptococcal glomerulonephritis. The treatment of SSTIs may at times necessitate both medical and surgical management. Various infections of the skin are a common reason for patients seeking attention from primary care providers; cellulitis was listed as the primary reason for office visits in approximately 2% of members of one health plan.1 It is therefore imperative that primary care providers have adequate knowledge of the appropriate evaluation and management of common SSTIs.

Bacterial infections of the skin can broadly be classified as primary or secondary (see Table 42-1).2 Primary bacterial infections usually involve areas of previously healthy skin and are typically caused by a single pathogen. In contrast, secondary infections occur in areas of previously damaged skin and are frequently polymicrobic. SSTIs are also classified as complicated or uncomplicated. Infections are considered complicated when they involve deeper skin structures (fascia, muscle layers, etc.), require significant surgical intervention, or occur in patients with compromised immune function (diabetes mellitus, human immunodeficiency virus [HIV], etc.).3

Table 42-1. Classification of Skin and Soft Tissue Infections Encountered in Primary Care2,5

The skin and subcutaneous tissues are normally extremely resistant to infection but may become susceptible under certain conditions. Even when high concentrations of bacteria are applied topically or injected into the soft tissue, resultant infections are rare. The majority of SSTIs result ...

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