Impetigo

General Information
- Primarily affects children, highly contagious.
Types of Impetigo
- Crusted or Nonbullous Impetigo
  - Presents with yellow crusts, erosions, itchy or irritating but not painful.
- Bullous Impetigo
  - Features rapid-eroding irritating blisters, usually caused by Staphylococcus aureus.
Causative Agents
- Nonendemic Settings:
  - Primarily S. aureus.
  - Less commonly Streptococcus pyogenes (Group A Streptococcus).
  - Possible co-infection with both bacteria.
- Endemic Settings:
  - Typically S. pyogenes, even if S. aureus is identified, including CA-MRSA.
Complications
- Wider spread infection: cellulitis, lymphangitis, and bacteraemia.
- Staphylococcal scalded skin syndrome.
- Scarlet fever.
- Post-streptococcal glomerulonephritis: a rare, acute renal condition following infection with Streptococcus pyogenes (group A streptococcus). This is due to a type III hypersensitivity reaction and presents 2–6 weeks post-skin infection.
- Streptococcal toxic shock syndrome: a rare complication causing diffuse erythematous rash, hypotension, and pyrexia.
- Postinflammatory pigmentation.
- Scarring, particularly with ecthyma.

Treatment Requirement: Antibiotic treatment is necessary for all impetigo cases.
Initial Management:
- Mild impetigo: Start empirical antibiotic therapy without initial skin swab; swab if no response.
- Severe disease: Require skin swab for culture and testing before empirical therapy.
Associated Conditions: Treat underlying dermatosis if present (e.g., dermatitis, scabies, head lice).
General measures
- Regular gentle cleansing; removal of honey-coloured crusts.
- Practice good hand hygiene and keep fingernails cut short.
- Cover the affected areas with watertight dressing to prevent spread.

Avoid touching affected areas.
Practice good hand hygiene; wash hands before and after applying creams.
Use a clean cloth each time to wash and dry affected areas.
Do not share towels or face cloths.
Clothing and bedding should be changed daily; wash using hot temperatures.
Avoid close contact with others — school/nursery children should stay home until lesions have crusted over, or they have received at least 24 hours of treatment.

Impetigo is usually self-limiting without serious complications. Without treatment, impetigo usually heals in 2–3 weeks; with treatment lesions resolve within 10 days.
Postinflammatory hypopigmentation or hyperpigmentation may occur but scarring is uncommon.
Recurrent impetigo may indicate nasal carriage of S. aureus. Following treatment, eradication of staphylococcal carriage may be necessary.

Nonendemic Settings:
- Localised Sores:
  - Mupirocin 2% ointment or cream, apply topically 8-hourly for 5 days.
- Multiple Sores or Recurrent Infection:
  - Dicloxacillin 500 mg (child: 12.5 mg/kg up to 500 mg) orally, 6-hourly for 7 days.
  - Flucloxacillin 500 mg (child: 12.5 mg/kg up to 500 mg) orally, 6-hourly for 7 days.
  - Cefalexin 500 mg (child: 12.5 mg/kg up to 500 mg) orally, 6-hourly for 7 days, or 1 g (child: 25 mg/kg up to 1 g) orally, 12-hourly for 7 days.
  - For penicillin-allergic patients: Trimethoprim+sulfamethoxazole (TMP-SMX) 160+800 mg (child 1 month or older: 4+20 mg/kg up to 160+800 mg) orally, 12-hourly for 3 days, or 320+1600 mg (child 1 month or older: 8+40 mg/kg up to 320+1600 mg) orally, daily for 5 days.
Endemic Settings:
- Benzathine benzylpenicillin (single dose intramuscularly): Adult: 1.2 million units; Child <10 kg: 0.45 million units; Child 10 kg to <20 kg: 0.6 million units; Child ≥20 kg: 1.2 million units.
- TMP-SMX 160+800 mg (child 1 month or older: 4+20 mg/kg up to 160+800 mg) orally, 12-hourly for 3 days, or 320+1600 mg (child 1 month or older: 8+40 mg/kg up to 320+1600 mg) orally, daily for 5 days.