Topical Treatment of Impetigo
Topical mupirocin 2% ointment applied twice daily for 5 days is the recommended first-line treatment for localized, uncomplicated impetigo. 1
Causative Organisms and Diagnosis
Impetigo is a highly contagious, superficial skin infection caused by:
- Staphylococcus aureus (most common)
- Streptococcus pyogenes (Group A streptococcus)
- Or both organisms simultaneously
There are two main types:
- Nonbullous impetigo (70% of cases): characterized by honey-colored crusts
- Bullous impetigo (30% of cases): characterized by flaccid bullae, exclusively caused by S. aureus
While Gram stain and culture can help identify the causative organism, treatment without these studies is reasonable in typical cases 1.
Treatment Algorithm
1. Localized, Uncomplicated Impetigo
First-line therapy: Topical mupirocin 2% ointment applied twice daily for 5 days 1, 2
Alternative topical option: Retapamulin applied twice daily for 5 days 1
2. When to Use Oral Antibiotics Instead
Oral antibiotics are recommended when:
- Patient has numerous or widespread lesions
- During outbreaks affecting several people (to decrease transmission)
- Signs of systemic illness are present
- Significant lymphadenopathy is present
- Infection fails to respond to topical therapy after 3-4 days
- Multiple household members are affected 1, 3
3. Oral Antibiotic Options (7-day regimen)
- For methicillin-susceptible S. aureus: Dicloxacillin or cephalexin 1
- For MRSA (suspected or confirmed): Doxycycline, clindamycin, or sulfamethoxazole-trimethoprim (SMX-TMP) 1
- For streptococci alone: Oral penicillin 1
Efficacy Considerations
Topical mupirocin has been shown to be:
- As effective as oral erythromycin in clinical trials (93% vs 78.5% efficacy) 2
- Effective at pathogen eradication (94-100% in clinical trials) 2
- Similar in efficacy to other topical agents like fusidic acid against S. aureus, but superior against S. pyogenes 4
Important Clinical Pearls
- Duration of therapy: Complete the full 5-day course even if lesions appear to be improving earlier 3
- Expected response: Improvement should be seen within 3-4 days of starting treatment 3
- Prevention of spread: Regular bathing, avoiding sharing personal items, and washing hands frequently can help prevent transmission 3
- Household management: Consider evaluating household contacts for similar infections to prevent further spread 3
- Complications: While rare, the most serious potential complication is poststreptococcal glomerulonephritis 5
- Antibiotic resistance: Be aware of increasing prevalence of resistant bacteria, including MRSA, macrolide-resistant streptococcus, and mupirocin-resistant strains 5
Special Considerations
- Pediatric patients: Mupirocin is effective and well-tolerated in children as young as 2 months 2
- Systemic therapy preference: During outbreaks affecting multiple people, systemic therapy is preferred to help decrease transmission 3
- Topical disinfectants: These are inferior to antibiotics and should not be used 5, 6
By following this treatment algorithm, most cases of impetigo will resolve within 2-3 weeks without scarring, with significant improvement typically seen within 3-4 days of initiating appropriate therapy.