Impetigo

Basics

Description

  • Impetigo is a common, highly contagious bacterial infection of the superficial layers of the epidermis
  • Primary infection:
    • Infection of previously normal skin by direct bacterial invasion
  • Secondary infection:
    • Infection at site of minor skin trauma or previously existing skin lesions
  • Most prevalent in children aged 2–5 yr
  • More common in summer months and warm and humid climates
  • Easily spread among individuals in close contact
  • Predisposing factors:
    • Minor trauma, especially around nasal area
    • Burns
    • Insect bites
    • HIV infection
    • Diabetes mellitus
    • Existing skin disease
    • Varicella infection
    • Immunocompromise
  • Complications:
    • Acute poststreptococcal glomerulonephritis:
      • 1–5% in patients with nonbullous impetigo
    • Sepsis
    • Cellulitis
    • Endocarditis
    • Toxic shock syndrome (TSS)
    • Staphylococcal-scalded skin syndrome (SSSS)

Etiology

  • Classic (nonbullous) impetigo:
    • The result of bacteria entering through traumatic skin portal from scratch, abrasion, wound, or insect bite
    • Most common form
    • Caused by Staphylococcus aureus, group A β-hemolytic streptococci (GABHS), or both
    • Often associated with poor hygiene
    • Treatment of both streptococci and S. aureus
  • Bullous impetigo:
    • Almost exclusively caused by S. aureus
    • Epidermal cleavage is caused by staphylococcal exfoliative toxins A, B, and D, which are serine proteases that bind and cleave desmoglein 1, an intercellular adhesion molecule in desmosomes

Pregnancy Considerations

Zinc supplementation to mother during pregnancy may lead to decreased incidence in infants

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