What are the typical presentation and treatment of impetigo?

Impetigo: Presentation and Treatment

Topical mupirocin is the first-line treatment for localized impetigo, applied 2-3 times daily for 5-7 days, while oral antibiotics should be reserved for extensive disease. 1

Clinical Presentation

Nonbullous Impetigo (70% of cases)

• Caused by Staphylococcus aureus or Streptococcus pyogenes 1, 2
• Characterized by:
  • Honey-colored crusts on face and extremities 2
  • Initially appears as small red macules
  • Progresses to vesicles that rupture and form golden-yellow crusts
  • Commonly affects exposed areas (face, arms, legs)
  • Highly contagious 3

Bullous Impetigo (30% of cases)

• Caused exclusively by S. aureus 2
• Characterized by:
  • Large, flaccid bullae (fluid-filled blisters)
  • More likely to affect intertriginous areas 2
  • Fragile vesicles that rupture easily
  • Thin, varnish-like crust after rupture
  • Most common in children under 5 years, particularly neonates 4

Diagnostic Approach

• Diagnosis is primarily clinical based on characteristic appearance 3, 2
• Bacterial culture may be obtained from active lesions to:
  • Identify causative organism
  • Determine antibiotic sensitivities
  • Guide therapy in recalcitrant cases 1

Treatment Guidelines

Localized Impetigo

• First-line: Topical mupirocin 2% ointment

  • Apply to affected areas 2-3 times daily for 5-7 days 1
  • Clinical efficacy rates of 71-93% 5
  • FDA-approved for impetigo due to S. aureus and S. pyogenes 5
  • Superior to placebo with pathogen eradication rates of 94% 5

• Alternative topical options:

  • Retapamulin: No resistance reported yet 6
  • Fusidic acid: Similar efficacy to mupirocin 1, 2

Extensive Impetigo

• Oral antibiotics recommended for widespread infection 1, 3

• First-line options:

  • For MSSA: Dicloxacillin or cephalexin 1
  • For suspected/confirmed MRSA: Doxycycline, clindamycin, or trimethoprim-sulfamethoxazole 1
  • Standard duration: 7 days 1

• Important considerations:

  • Avoid doxycycline in children under 8 years 1
  • Adjust dosing by weight for children 1
  • Oral penicillin V is seldom effective 3, 2
  • Amoxicillin-clavulanate: 875/125 mg twice daily for 7 days 1
  • Clindamycin: 300 mg three times daily for 7 days 1

Treatment Efficacy Comparison

• Topical mupirocin is slightly superior to oral erythromycin (RR 1.07) 6
• Mupirocin and fusidic acid have similar efficacy (RR 1.03) 6
• Topical antibiotics are superior to disinfectants (RR 1.15) 6
• Erythromycin is superior to penicillin (RR 1.29) 6

Common Pitfalls and Considerations

• Failing to consider MRSA in recalcitrant cases 1
• Using penicillin, which is inferior to other antibiotics 1, 6
• Inadequate treatment duration 1
• Relying solely on topical therapy for extensive disease 1
• Not addressing underlying conditions predisposing to recurrent infection 1
• Topical disinfectants are inferior to antibiotics and should not be used 3, 6

Prevention and Control

• Good personal hygiene practices:

  • Regular handwashing
  • Keeping draining wounds covered
  • Avoiding sharing personal items 1
  • Using separate towels and linens 1

• For recurrent infections:

  • Consider 5-day decolonization regimen with intranasal mupirocin, daily chlorhexidine washes, and decontamination of personal items 1
  • Evaluate for underlying immunodeficiency if recurrence happens more than 3 times 1
  • Prophylactic antibiotics may be considered for frequent recurrences (3-4 episodes per year) 1

Expected Outcomes

• Resolution typically occurs within 7-10 days of starting appropriate treatment 1
• Clinical response should be evident within 48-72 hours 1
• Consider alternative antibiotics if no improvement within 3-5 days 1
• Complications are rare, with poststreptococcal glomerulonephritis being the most serious 1, 2, 7