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Skin and soft tissue infections (SSTI) are characterized by clinical findings that include an acute, tender, spreading, edematous, suppurative inflammation of the skin, subcutaneous fat, or muscle, often associated with systemic symptoms of malaise, fever, chills, and local pain. Cellulitis is an infection of the dermis and subcutaneous fat, while erysipelas is a more superficial variant affecting the superficial dermal lymphatics and adjacent tissues. Along with the pyodermas (see Chapter 176), cellulitis and erysipelas, are the predominant forms of non-necrotizing SSTI, which account for 7%–10% of hospitalizations in North America.1 Over the past two decades, the incidence of SSTI has increased faster than the incidence of other acute infections, paralleling the rise of methicillin-resistant Staphylococcus aureus (MRSA) rates.2
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Cellulitis and erysipelas are usually caused by S. aureus or β-hemolytic Streptococci [primarily group A Streptococcus (GAS)] (see Table 178-1). Factors that increase the likelihood of SSTI include exposure to pathogenic organisms, local breach of the skin barrier function (including atopic dermatitis, and less often, allergic contact dermatitis, psoriasis, trauma, intravenous drug use, surgical and cosmetic procedures, toe-web intertrigo, arthropod bites, and chronic ulcers), immunocompromise (including acquired immunodeficiency syndrome [AIDS], diabetes, end-stage renal disease/dialysis, neutropenia, cancer, and immunosuppressive medications), obesity, and circulatory compromise (see Chapter 175).
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