Clinical Manifestations and Treatment of Impetigo
Impetigo presents in two main forms - nonbullous (70% of cases) and bullous (30% of cases) - with characteristic lesions that require targeted antimicrobial therapy based on extent and severity of infection.
Clinical Manifestations
Nonbullous Impetigo (Impetigo Contagiosa)
- Caused by Staphylococcus aureus or Streptococcus pyogenes, or both in combination 1, 2
- Begins as erythematous papules that rapidly evolve into vesicles and pustules 1
- Vesicles rupture, with dried discharge forming characteristic honey-colored crusts on an erythematous base 1, 2
- Most commonly affects exposed areas, particularly the face and extremities 3, 2
Bullous Impetigo
- Caused exclusively by toxin-producing strains of S. aureus 1, 2
- Characterized by fragile, thin-roofed vesicopustules that form when toxins cleave the dermal-epidermal junction 1
- Lesions may rupture, creating crusted, erythematous erosions often surrounded by a collar of the roof's remnants 1
- More likely to affect intertriginous areas 2
Ecthyma
- A deeper infection than impetigo, caused by S. aureus and/or streptococci 1
- Begins as vesicles that rupture, resulting in circular, erythematous ulcers with adherent crusts 1
- Often presents with surrounding erythematous edema 1
- Unlike impetigo, ecthyma heals with scarring 1, 4
Treatment Approach
Diagnostic Evaluation
- Diagnosis is typically made clinically based on characteristic appearance 2
- Cultures of vesicle fluid, pus, erosions, or ulcers may be obtained to establish the cause, especially in cases of treatment failure, suspected MRSA, or recurrent infections 1, 5
Treatment Options
Topical Therapy (First-Line for Limited Disease)
- Topical mupirocin 2% ointment applied three times daily for 5-7 days is the first-line treatment for localized impetigo 5, 3, 6
- Topical retapamulin 1% ointment applied twice daily for 5 days is an effective alternative 5, 7
- Topical antibiotics have shown better cure rates than placebo (RR 2.24,95% CI 1.61 to 3.13) 7
- Topical therapy is preferred for limited disease due to fewer systemic side effects 3, 7
- Clinical efficacy rates for mupirocin are approximately 71-93% compared to 35% for placebo 6
Systemic Therapy (For Extensive Disease)
- Oral antibiotics should be used when impetigo is extensive, involves multiple sites, topical therapy is impractical, treatment with topical antibiotics has failed, or systemic symptoms are present 5, 3, 2
- For methicillin-susceptible S. aureus (MSSA):
- For methicillin-resistant S. aureus (MRSA):
- When streptococci alone are the cause, penicillin is the drug of choice 1
- For penicillin-allergic patients with streptococcal infections, a macrolide or clindamycin is recommended 1
Special Considerations
- Systemic antimicrobials should be used during outbreaks of poststreptococcal glomerulonephritis to help eliminate nephritogenic strains of Streptococcus pyogenes 1
- Oral antibiotic dosing should be adjusted by weight for children 5
- Tetracyclines (doxycycline, minocycline) should not be used in children under 8 years of age 5, 2
- Penicillin alone is not effective for impetigo as it lacks adequate coverage against S. aureus 3, 2
- Topical disinfectants are inferior to antibiotics and should not be used 2, 7
Treatment Duration and Follow-up
- Topical treatment should be used for 5-7 days 5, 3
- Oral antibiotics should be administered for 5-10 days 3
- Re-evaluate if no improvement after 48-72 hours of therapy 5, 3
- Lesions should be kept covered with clean, dry bandages and good personal hygiene maintained to prevent spread 5, 3
Common Pitfalls and Caveats
- Impetigo is highly contagious, so proper hygiene measures are essential to prevent spread 2
- Consider alternative diagnoses if the presentation is atypical or not responding to appropriate therapy 3
- Growing resistance rates for commonly used antibiotics must be considered when selecting treatment 7
- Complications are rare, with the most serious being poststreptococcal glomerulonephritis 2