What type of impetigo requires oral antibiotics?

Types of Impetigo Requiring Oral Antibiotics

Oral antibiotics are required for extensive impetigo, bullous impetigo with large bullae, and cases where topical therapy is impractical or has failed. 1

Classification of Impetigo and Treatment Approach

Impetigo presents in two main forms:

1. Nonbullous impetigo (70% of cases):

   • Characterized by honey-colored crusts on face and extremities
   • Caused by Staphylococcus aureus or Streptococcus pyogenes 2

2. Bullous impetigo (30% of cases):

   • Characterized by large, flaccid bullae
   • Exclusively caused by S. aureus
   • More likely to affect intertriginous areas 2

When to Use Oral Antibiotics

Oral antibiotics are indicated in the following scenarios:

• Extensive disease with multiple lesions over a large body surface area 1, 2
• Bullous impetigo with large bullae 2
• Impractical topical therapy (hard-to-reach areas or patient compliance issues) 2
• Failed topical therapy after 3-5 days of appropriate treatment 1
• High-risk populations where transmission prevention is critical 3
• Areas with high prevalence of nephritogenic strains of Streptococcus 3
• Severe or spreading lesions 3
• Poor hygiene conditions where risk of spread is high 3

Recommended Oral Antibiotics

For oral antibiotic therapy, the Infectious Diseases Society of America recommends:

• For MSSA (methicillin-susceptible S. aureus):

  • Dicloxacillin or cephalexin 1

• For suspected or confirmed MRSA:

  • Doxycycline (avoid in children <8 years)
  • Clindamycin
  • Sulfamethoxazole-trimethoprim (SMX-TMP) (note: inadequate for streptococcal coverage) 1, 2

• Standard duration: 7 days 1

When Topical Antibiotics Are Sufficient

Topical antibiotics are appropriate for:

• Localized impetigo with few lesions 1, 2
• Non-bullous impetigo that is not extensive 4

Effective topical options include:

• Mupirocin 2% ointment (2-3 times daily for 5-7 days)
• Retapamulin
• Fusidic acid (not FDA approved in US) 1, 5

Important Clinical Considerations

• Culture guidance: Obtain cultures from active lesions to identify causative organisms and antibiotic sensitivities, especially in recalcitrant cases 1

• Treatment response: Evaluate clinical response within 48-72 hours; consider alternative antibiotics if no improvement within 3-5 days 1

• Common pitfalls to avoid:

  • Failing to consider MRSA in treatment-resistant cases
  • Using penicillin alone (inferior to other antibiotics for impetigo)
  • Inadequate duration of therapy
  • Relying solely on topical therapy for extensive disease
  • Not addressing underlying conditions predisposing to recurrent infection 1

• Antibiotic resistance concerns: Consider local resistance patterns when selecting antibiotics, as MRSA, macrolide-resistant streptococcus, and mupirocin-resistant strains are increasingly prevalent 2, 5

Special Populations

• Children under 8 years: Avoid tetracyclines (doxycycline, minocycline) 1

• Recurrent infections: Consider evaluation for underlying immunodeficiency or neutrophil disorders if impetigo recurs more than 3 times 1