Humans are natural hosts for many bacterial species that colonize the skin as normal flora. Staphylococcus aureus and Streptococcus pyogenes are infrequent resident flora, but they account for a wide variety of bacterial pyodermas. Predisposing factors to infection include minor trauma, preexisting skin disease, poor hygiene, and, rarely, impaired host immunity.

Impetigo

Impetigo is a superficial skin infection usually caused by S. aureus and occasionally by S. pyogenes.

Prevalence and Risk Factors

Impetigo affects approximately 1% of children.

Pathophysiology and Natural History

S. aureus produces a number of cellular and extracellular products, including exotoxins and coagulase, that contribute to the pathogenicity of impetigo, especially when coupled with preexisting tissue injury. Impetigo commonly occurs on the face (especially around the nares) or extremities after trauma.

Signs and Symptoms

Two clinical types of impetigo exist: nonbullous and bullous. The nonbullous type is more common and typically occurs on the face and extremities, initially with vesicles or pustules on reddened skin. The vesicles or pustules eventually rupture to leave the characteristic honey-colored (yellow-brown) crust. Bullous impetigo, almost exclusively caused by S. aureus, exhibits flaccid bullae with clear yellow fluid that rupture and leave a golden-yellow crust.

Diagnosis

Diagnosis is by clinical presentation and confirmation by culture.1

Treatment

For most patients with impetigo, topical treatment is adequate, either with bacitracin (Polysporin) or mupirocin (Bactroban), applied twice daily for 7 to 10 days. Systemic therapy may be necessary for patients with extensive disease