Definition
• Infection of superficial, deep dermis, subcutaneous fat, and lymphatic system in the absence of an underlying suppurative focus
Microbiology
• Skin flora: Strep/staph (increasingly, CA-MRSA)
• Dog/cat bites: Pasteurella multocida, bacteroides, Fusobacterium, Erysipelothrix
• Human bites: Eikenella
• Fresh water exposure: Vibrio vulnificus
• Puncture wounds/piercings: Pseudomonas
Clinical Manifestations
• Pain, warmth, swelling, erythema, tender LAD of draining LN, may or may not have assoc abscess, lymphangitis. Less commonly systemic sx → fevers, chills, myalgias
• Red flags (see Ddx below): Pain out of proportion to clinical findings, rapidly progressive erythema, paresthesias, crepitus, bullae, or signs of systemic toxicity
Differential Diagnosis
• Distinguished from other potentially fatal infxn’s, including necrotizing fasciitis and clostridial myonecrosis. Eval for underlying process, such as collection, septic arthritis, or osteomyelitis
• Erythema migrans, foreign body reactions, folliculitis, drug reactions, insect stings, contact dermatitis, lymphedema, DVT
Diagnostic Studies (N Engl J Med 2004;350:904)
• Virtually always a clinical dx as blood cultures have low yield (∼2%)
• Radiographs not necessary for routine evaluation of patients w/ cellulitis
• U/S if collections suspected
• Cx’s of drainage, pus, bullae. Cx’s of intact skin are generally not helpful
Treatment
• Incision and drainage of any large collection of fluid within the pustule or abscess
• Warm compresses and soaks to facilitate spontaneous drainage
• Elevation of limb to decrease edema
• For CA-MRSA infections, effectiveness of decolonization uncertain (Lancet Infect Dis 2011;11:952)
• Antibiotic Rx
• Outpt → cephalexin, dicloxacillin. If CA-MRSA rates ↑, known colonization or previous infection w/ CA-MRSA and other MRSA risk factors, consider empiric TMP–SMX or clindamycin. However, the utility of antibiotics in uncomplicated superficial infections is uncertain (Pediatrics 2011;127:e573; J Pediatr 2011;158:861–862. commentary)
• Inpt → IV nafcillin, cefazolin, clindamycin. If concern for MRSA, unresponsive or severe disease → IV vancomycin first line; alternative: Linezolid