Impetigo

Highly infectious superficial skin infection that typically affects children

Aetiology

  • Most common in children
Main causative organisms:
  • Staphylococcus aureus (most common today)
  • Group A β-hemolytic Streptococcus (Streptococcus pyogenes)
  • Mixed infections also possible
Associated risk factors:
  • Poor hygiene
  • Warm, humid environments
  • Skin trauma, insect bites, eczema
  • Close contact (schools, daycare)

Pathophysiology

  • Infection immediately below surface
  • Superficial (stratum corneum) and localised
  • Entry point - small defect in skin
  • Highly contagious with discharge on the face, scratching due to irritation can aid spread

Clinical Presentation

Types of Impetigo

Non-bullous Impetigo (most common)

  • Usually due to Streptococcus pyogenes
  • Begins with small vesicles → pustules → rupture
  • Forms golden/honey-colored crusts
  • Lesions often around nose & mouth
  • Regional lymphadenopathy may occur
  • Pruritus common → scratching spreads infection
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Bullous Impetigo

  • Caused primarily by Stapyhlococcus aureus producing exfoliative toxin
  • Large flaccid bullae with clear/yellow fluid
  • Less crusting; skin appears moist after rupture
  • Common in infants & neonates
  • No systemic symptoms usually
  • Related to Staphylococcal Scalded Skin Syndrome (more severe form)
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Ecthyma (deep/ulcerative impetigo)

  • Most often appear in feet
  • Ulcerative form extending into the dermis
  • Lesions become "punched-out" ulcers with thick crust
  • More painful & slower healing
  • May scar
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Investigations

  • Usually clinical diagnosis
  • Bacterial swab for culture and sensitivity may be useful if:
    • The impetigo is extensive or severe
    • MRSA is suspected
    • The impetigo is recurrent or failing to respond to treatment

Management

General measures:
  • Gentle cleansing with soap & water
  • Remove crusts with 30-60 minutes warm compress 3x/day
    • Permanganas Kalicus 1:5000
    • Rivanol 1%
  • Hand hygiene; avoid scratching
Topical antibiotics (first-line for mild/localized disease) for 7 days:
  • Fusidic Acid 2%
  • Mupirocin 2%
  • Bacitracin 5%
  • Chloramphenicol 2%
Systemic Antibiotics (if topical fails or deep pyoderma)
  • First-line
    • Dicloxacillin
      • Adult → 250-500 mg 4x1
      • Child → 25-50 mg/kg/day (divided to 4 doses)
    • Cephalexin
      • 25-50 mg/kg/day (divided to 4 doses)
    • Amoxicillin-clavulanate
      • Adult → 250-500 mg 3x1
      • Child → 25 mg/kg/day (divided to 3 doses)
  • Second-line
    • Azithromycin 500 mg 1x1 (H1), 250 mg 1x1 (H2-5)
    • Clindamycin 300 mg 3x1, 15 mg/kg/day (divided to 3 doses)
    • Erithromycin 250-500 mg 4x1