Impetigo is a frequently observed superficial, very contagious, bacterial infection which can be divided in a non-bullous and a bullous form. Non-bullous impetigo accounts for more than 70% of cases of impetigo. It is frequently diagnosed in regions with a warm humid climate. Overcrowding, malnutrition and lack of hygiene also play an important role.
Etiology and pathogenesis
The predominant cause of non-bullous impetigo is Staphylococcus aureus although also Streptococcus pyogenes can be involved, especially in tropical countries. Bullous impetigo is nearly always caused by a coagulase positive S. aureus. These bacteria belong to a specific group (phage group 2) which produces an exfoliative toxin responsible for the blister formation. Phage group 2 S. aureus are also responsible for the development of the staphylococcal scalded skin syndrome (SSSS) which occurs mainly in neonates and infants.
Impetigo usually occurs on exposed areas like the face and extremities. Non-bullous impetigo starts often with a pustule which can develop rapidly and lead to the formation of yellow or brown colored crusts. Usually there is no pain but the lesions may be itchy. In the majority of cases regional lymphadenopathy can be found. Bullous impetigo presents with large blisters which rupture easily. They are usually localized on the face, extremities and the diaper area and they heal without scarring.
- Herpes simplex
- Insect bites (hypersensitivity response)
- Trauma (thermal)
- Impetigo is highly contagious, spreading needs to be prevented. Do not share the same towels and change clothes and towels frequently.
- In limited cases local therapy is usually sufficient. Wash with betadine shampoo daily and apply gentian violet paint 0.5%, mupirocin ointment, fusidic acid cream, sulphur 5% in zinc oxide cream or betadine ointment twice daily on the lesions.
- In moderate /severe cases an oral antibiotic, active against both streptococci and staphylococci (also beta-lactamase producing strains) like dicloxacillin is the drug of first choice. In case of penicillin-allergic patients, erythromycin can be given. When MRSA is suspected, cefalexin is an option.
Oral antibiotic, active against both S. pyogenes and S. aureus
Flucloxacillin (British National Formulary)
- Child under 2 years: quarter of the adult dose: 62.5-125 mg every 6 hours. Oral solution (Syrup, flucloxacillin, 25 mg/1mL) 2.5 mL-5 mL 4 times daily.
- Child 2-10 years : half of the adult dose: 125mg-250mg every 6 hours. Oral solution (Syrup, flucloxacillin, 25 mg/mL) 5 mL 4 times daily or Capsules (flucloxacillin, 250 mg) 1 capsule 4 times daily.
- Child above 10 years: adult dose: 250-500 mg 4 times daily.Capsules (flucloxacillin, 250 mg or 500 mg) 1 capsule 4 times daily.
Erythromycin (British National Formulary)
- Child up to 2 years: 125 mg 4 times daily.Oral solution (Syrup, erythromycin, 25 mg/1mL) 5mL 4 times daily.
- Child 2-8 years: 250 mg 4 times daily.Oral solution (Syrup, 50 mg/1mL) 5 mL 4 times daily or Capsules (erythromycin, 250mg) 1 capsule 4 times daily.
- Child above 8 years: adult dose: 250-500 mg 4 times daily.Capsules (erythromycin, 250 mg or 500 mg) 1 capsule 4 times daily.
Cefalexin (British National Formulary)
- Child under 1 year: 125 mg every 12 hours.Oral solution (Syrup, cefalexin 25 mg/1mL) 5 mL 2 times daily.
- Child 1-5 years: 125 mg every 8 hours.Oral solution (Syrup, cefalexin 25 mg/1mL) 5 mL 3 times daily.
- Child 6-12 years: 250 mg every 8 hours.Oral solution (Syrup, cefalexin 50 mg/1mL) 5 mL 3 times daily or Capsules (cephalexin 250 mg) 1 capsule 3 times daily.
- Above 12 years: adult dose: 250 mg every 6 hours or 500mg every 12 hours.Capsules (cefalexin 250 mg) 1 capsule 4 times daily or 2 capsules 2 times daily or 1 capsule (cefalexin 500mg) 2 times daily.
Reference list see Pyoderma