Impetigo: Treatment and Prevention
Overview and Etiology
Impetigo is a highly contagious superficial bacterial skin infection most commonly affecting children aged 2-5 years, caused by Staphylococcus aureus and/or Streptococcus pyogenes, requiring antibiotic therapy for optimal management. 1, 2
The infection presents in two forms:
- Nonbullous impetigo (70% of cases): Characterized by honey-colored crusts, typically on the face and extremities 2
- Bullous impetigo (30% of cases): Caused exclusively by S. aureus, presenting with large flaccid bullae, often in intertriginous areas 2
The pathogenesis involves initial colonization of unbroken skin (approximately 10 days before lesions appear), followed by inoculation through minor trauma, abrasions, or insect bites 3
Treatment Algorithm
For Limited/Localized Disease
First-line treatment is topical mupirocin 2% ointment applied three times daily for 5-7 days. 1, 4
- Mupirocin demonstrates 71% clinical efficacy versus 35% for placebo, with 94% pathogen eradication rates 4
- Alternative: Retapamulin 1% ointment applied twice daily for 5 days 1
- Both agents provide coverage against S. aureus and S. pyogenes 1
Important caveat: Topical therapy is appropriate when lesions are few in number and confined to small areas 1, 5
For Extensive Disease or When Topical Therapy Fails
Oral antibiotics are indicated when impetigo is extensive, involves multiple sites, topical therapy is impractical, topical treatment has failed, or systemic symptoms are present. 1, 5
For Methicillin-Susceptible S. aureus (MSSA):
- Dicloxacillin: 250 mg four times daily (adults) 5
- Cephalexin: 250-500 mg four times daily (adults) 5
- Pediatric dosing should be weight-based 5
For Suspected or Confirmed MRSA:
Consider MRSA coverage when there is failure to respond to first-line therapy, high local MRSA prevalence, or patient risk factors for CA-MRSA. 1
- Clindamycin: 300-450 mg three times daily (adults) 5
- Trimethoprim-sulfamethoxazole (TMP-SMX) 1, 5
- Doxycycline: Not for children under 8 years 5
Critical pitfall: Penicillin alone is NOT effective for impetigo due to inadequate S. aureus coverage 5, 6
Comparative Efficacy
Topical mupirocin is slightly superior to oral erythromycin (93% vs 78.5% clinical efficacy) and should be preferred for localized disease. 4, 7
- Topical antibiotics demonstrate better cure rates than placebo (pooled RR 2.24,95% CI 1.61-3.13) 7
- Mupirocin and fusidic acid show equivalent efficacy (RR 1.03,95% CI 0.95-1.11) 7
- Oral antibiotics have higher rates of side effects, primarily gastrointestinal 7
Treatment Duration and Monitoring
Complete the full antibiotic course even if symptoms improve quickly to prevent complications such as post-streptococcal glomerulonephritis. 1
- Topical therapy: 5-7 days 1, 5
- Oral therapy: 5-10 days 5
- Re-evaluate if no improvement after 48-72 hours 5
Special Situations
Nasal Impetigo
- Apply mupirocin 2% ointment to affected areas three times daily for 5-7 days 8
- For recurrent infections: Mupirocin ointment twice daily in anterior nares for the first 5 days each month reduces recurrences by approximately 50% 8
- Clindamycin 150 mg daily for 3 months may decrease subsequent infections by approximately 80% in persistent nasal colonization 8
Scalp Impetigo
- Same treatment algorithm as other sites 5
- Oral antibiotics preferred when multiple scalp sites are involved 5
Treatment Failure
Obtain cultures of vesicle fluid, pus, or erosions if treatment fails, MRSA is suspected, or recurrent infections occur. 5
- Adjust therapy based on susceptibility results 5
- Consider alternative diagnoses if not responding to appropriate therapy 5
Prevention Strategies
Maintain good personal hygiene as streptococcal organisms initially colonize unbroken skin before causing infection. 3
- Keep lesions covered with clean, dry bandages to prevent spread 5
- Address minor skin trauma, insect bites, and underlying conditions (eczema) promptly 3, 2
- Avoid sharing personal items during active infection 2
Antimicrobial Resistance Considerations
Growing bacterial resistance rates worldwide necessitate judicious antibiotic selection and consideration of local resistance patterns. 2, 9
- Methicillin-resistant S. aureus (MRSA) prevalence is increasing 2
- Macrolide-resistant streptococcus and mupirocin-resistant streptococcus are documented 2
- Erythromycin resistance rates are rising 6
- Avoid topical disinfectants as they are inferior to antibiotics (RR 1.15,95% CI 1.01-1.32 favoring antibiotics) 7
Key Clinical Pearls
- Impetigo typically resolves within 2-3 weeks without scarring, but treatment improves cosmesis, reduces discomfort, and prevents spread 2, 6
- Complications are rare, with post-streptococcal glomerulonephritis being the most serious 2
- Side effects from topical therapy are minimal compared to oral antibiotics 4, 7
- Tetracyclines should never be used in children under 8 years of age 5