Impetigo: diagnosis and treatment

Impetigo is the most common bacterial skin infection in children two to five years of age. There are two principal types: nonbullous (70% of cases) and bullous (30% of cases). Nonbullous impetigo, or impetigo contagiosa, is caused by Staphylococcus aureus or Streptococcus pyogenes, and is characterized by honey-colored crusts on the face and extremities. Impetigo primarily affects the skin or secondarily infects insect bites, eczema, or herpetic lesions. Bullous impetigo, which is caused exclusively by S. aureus, results in large, flaccid bullae and is more likely to affect intertriginous areas. Both types usually resolve within two to three weeks without scarring, and complications are rare, with the most serious being poststreptococcal glomerulonephritis. Treatment includes topical antibiotics such as mupirocin, retapamulin, and fusidic acid. Oral antibiotic therapy can be used for impetigo with large bullae or when topical therapy is impractical. Amoxicillin/clavulanate, dicloxacillin, cephalexin, clindamycin, doxycycline, minocycline, trimethoprim/sulfamethoxazole, and macrolides are options, but penicillin is not. Natural therapies such as tea tree oil; olive, garlic, and coconut oils; and Manuka honey have been anecdotally successful, but lack sufficient evidence to recommend or dismiss them as treatment options. Treatments under development include minocycline foam and Ozenoxacin, a topical quinolone. Topical disinfectants are inferior to antibiotics and should not be used. Empiric treatment considerations have changed with the increasing prevalence of antibiotic-resistant bacteria, with methicillin-resistant S. aureus, macrolide-resistant streptococcus, and mupirocin-resistant streptococcus all documented. Fusidic acid, mupirocin, and retapamulin cover methicillin-susceptible S. aureus and streptococcal infections. Clindamycin proves helpful in suspected methicillin-resistant S. aureus infections. Trimethoprim/sulfamethoxazole covers methicillin-resistant S. aureus infection, but is inadequate for streptococcal infection.