Skin and Soft Tissue Infections

Skin and soft tissue infections range from mild bacterial infections of the dermis and lymphatic system, such as erysipelas, to rapidly spreading necrotizing fasciitis. Mild infections are often caused by methicillin-sensitive Staphylococcus aureus and Streptococcus species, whereas more severe infections are often polymicrobial and involve anaerobic bacteria. Purulent skin infections are more likely to be caused by methicillin-resistant S aureus (MRSA). Nasal polymerase chain reaction testing for MRSA may be helpful for skin infections associated with a wound, but it cannot rule out MRSA as the cause of simple cellulitis or abscess. Before diagnosing cellulitis, clinicians should consider other possible causes such as venous stasis dermatitis and deep venous thrombosis. Bilateral cellulitis is rare. Cellulitis is a clinical diagnosis, but white blood cell count can indicate severity. Nonpurulent, mild cellulitis should be treated with penicillin or first-generation cephalosporins for 5 days. For nonpurulent, severe infections, antibiotic therapy that covers MRSA and anaerobic bacteria is warranted. Point-of-care ultrasonography can reliably differentiate cellulitis from abscess. Abscesses should be treated with incision and drainage, followed by antibiotics such as clindamycin or trimethoprim/sulfamethoxazole to reduce the risk of treatment failure. Recurrence of cellulitis is common, occurring in as many as 29% of cases. Risk factors for recurrence include lymphedema, dependent lower extremity edema, and malignancy.