What causes recurrent impetigo?

Causes of Recurrent Impetigo

Recurrent impetigo is primarily caused by persistent colonization with Staphylococcus aureus (particularly in the nasal passages) or Streptococcus pyogenes, combined with inadequate treatment of initial infections and poor personal hygiene practices. 1, 2

Causative Organisms

• Primary pathogens:
  • Staphylococcus aureus - responsible for most cases of nonbullous impetigo (70%) and all cases of bullous impetigo (30%) 3
  • Streptococcus pyogenes (Group A beta-hemolytic streptococci) - causes some cases of nonbullous impetigo 1

Key Factors Contributing to Recurrence

1. Colonization Patterns

• Nasal carriage of S. aureus is the primary reservoir for recurrent skin infections 2
  • S. aureus colonizes the nasal epithelium first, then spreads to skin
  • Streptococci directly bind to fibronectin sites on skin exposed by trauma 2

2. Inadequate Initial Treatment

• Insufficient duration of antibiotic therapy
• Use of ineffective antibiotics (particularly with resistant strains)
• Incomplete drainage of associated abscesses 1
• Failure to address colonization sites 1

3. Antibiotic Resistance

• MRSA (Methicillin-resistant S. aureus) - increasingly common in community settings 1
• Mupirocin resistance - emerging issue with topical treatment 1
• Macrolide resistance in streptococci - increasing from 4-5% to 8-9% in recent surveillance 1

4. Environmental and Behavioral Factors

• Poor personal hygiene 1
• Household transmission - sharing personal items 1
• Crowded living conditions 1
• Contact sports participation 1
• Inadequate wound care of minor skin trauma 1

5. Host Factors

• Pre-existing skin conditions that disrupt skin barrier:
  • Eczema
  • Dermatitis
  • Insect bites 3
• Diabetes and other immunocompromising conditions 1
• Venous insufficiency or lymphedema (particularly for lower extremity infections) 4

Pathophysiology of Recurrence

The pathogenesis of recurrent impetigo involves a complex interplay between:

1. Persistent colonization - S. aureus can survive in nasal passages, perineum, and other body sites despite treatment of visible skin lesions 1

2. Auto-inoculation - patients transfer bacteria from colonized sites to areas of minor skin trauma 2

3. Household contamination - bacteria can persist on household surfaces and be reintroduced to skin 1

4. Toxin production - particularly with bullous impetigo, where S. aureus produces exfoliative toxins that damage the epidermis 5

Prevention of Recurrence

To prevent recurrent impetigo, a comprehensive approach should address:

1. Decolonization of the patient when recurrent episodes occur:

   • Nasal mupirocin twice daily for 5-10 days 1
   • Consider adding chlorhexidine body washes or dilute bleach baths 1

2. Household hygiene measures:

   • Avoid sharing personal items (towels, razors, clothing) 1
   • Regular cleaning of high-touch surfaces 1
   • Proper laundering of clothing and bedding 1

3. Proper wound care:

   • Cover open wounds 1
   • Prompt cleaning and treatment of minor skin trauma 1

4. Screening and treatment of household contacts when transmission is suspected 1

Common Pitfalls in Managing Recurrent Impetigo

• Failure to identify and treat nasal carriers of S. aureus 2
• Inadequate attention to personal and environmental hygiene measures 1
• Not considering MRSA in treatment failures 1
• Overuse of antibiotics leading to resistance development 1
• Not addressing underlying skin conditions that predispose to recurrence 3

By addressing colonization, ensuring adequate treatment of initial infections, implementing proper hygiene measures, and treating household contacts when necessary, most cases of recurrent impetigo can be effectively managed.