What are the presentation and treatment of impetigo?

Impetigo: Presentation and Treatment

Impetigo should be treated with topical mupirocin 2% ointment applied 3 times daily for 5-7 days for localized lesions, while oral antibiotics are indicated for extensive disease. 1, 2

Clinical Presentation

Nonbullous Impetigo (70% of cases)

• Caused by Staphylococcus aureus or Streptococcus pyogenes 3
• Characterized by:
  • Honey-colored crusts on face and extremities
  • May secondarily infect insect bites, eczema, or herpetic lesions
  • Most common in children 2-5 years of age

Bullous Impetigo (30% of cases)

• Caused exclusively by Staphylococcus aureus 3
• Characterized by:
  • Large, flaccid bullae
  • More likely to affect intertriginous areas

Both types typically resolve within 2-3 weeks without scarring, with complications being rare 3.

Diagnostic Approach

• Diagnosis is primarily clinical based on characteristic appearance
• Obtain cultures from active lesions to identify the causative organism and antibiotic sensitivities in cases of:
  • Treatment failure
  • Recurrent infections
  • Suspected MRSA 1

Treatment Algorithm

1. Localized Impetigo (Limited Lesions)

• First-line: Topical antibiotics 1, 2
  • Mupirocin 2% ointment applied to affected areas 3 times daily for 5-7 days
  • Clinical efficacy rates of 71-93% for mupirocin versus 35% for placebo 2
  • Retapamulin and fusidic acid are alternatives with similar efficacy 1, 4

2. Extensive Impetigo (Multiple Lesions or Widespread)

• Oral antibiotics recommended 1, 3
  • For MSSA (Methicillin-Susceptible S. aureus):
    • Dicloxacillin: 250-500 mg 4 times daily for adults; 12.5-25 mg/kg/day in 4 divided doses for children
    • Cephalexin: 250-500 mg 4 times daily for adults; 25 mg/kg/day in 4 divided doses for children
  • For suspected or confirmed MRSA:
    • Clindamycin: 300-450 mg 3 times daily for adults; 10-20 mg/kg/day in 3 divided doses for children
    • Trimethoprim-sulfamethoxazole: 1-2 double-strength tablets twice daily for adults; 8-12 mg/kg/day in 2 divided doses for children
    • Doxycycline: 100 mg twice daily for adults (not for children under 8 years) 1
  • Standard duration: 7 days 1

Important Clinical Considerations

Antibiotic Resistance

• Growing resistance rates for commonly used antibiotics worldwide 5
• Penicillin is inferior to other antibiotics and should not be used 3, 4
• Consider MRSA as a causative organism in recalcitrant cases 1

Monitoring Response

• Evaluate clinical response within 48-72 hours of starting treatment
• Consider alternative antibiotics if no improvement is seen within 3-5 days 1

Prevention Measures

• Good personal hygiene practices are essential:
  • Regular handwashing
  • Keep draining wounds covered
  • Avoid sharing personal items
  • Use separate towels and linens 1
• For recurrent infections, consider a 5-day decolonization regimen:
  • Intranasal mupirocin twice daily
  • Daily chlorhexidine washes
  • Daily decontamination of personal items 1

Common Pitfalls to Avoid

• Using topical disinfectants, which are inferior to antibiotics 3, 4
• Inadequate duration of therapy
• Relying solely on topical therapy for extensive disease
• Not addressing underlying conditions that predispose to recurrent infection 1
• Using penicillin, which has been shown to be inferior to other antibiotics 1

Special Populations

• For children under 8 years: Avoid tetracyclines (doxycycline, minocycline) 1
• For patients with frequent recurrences (3-4 episodes per year): Consider prophylactic antibiotics 1
• For patients with more than 3 recurrences: Evaluate for underlying immunodeficiency or neutrophil disorders 1