Impetigo and other Pyoderma

Essentials

• Impetigo spreads easily in the family, day-care centre and school.
• Remember the possibility of post-infectious glomerulonephritis in streptococcal impetigo.

Clinical features

• Children are most commonly affected.
• Streptococcal infection typically makes crusts or small ulcerations; staphylococcal infection tends to make blisters (pictures ).
• "Pemphigus neonatorum" (picture ) in infants is actually impetigo. The infection is caused by Staphylococcus aureus phage type II.
• The crusts usually appear in the surroundings of the nostrils (picture ), on the chin (picture ), and generally on the face (pictures ).
• Thick crusts are characteristic.

Differential diagnosis

• Primary herpes simplex infection may resemble impetigo.
• Ringworm (tinea corporis)
• If impetigo tends to recur in the scalp and neck consider the possibility of head lice.

Causative agents

• Staphylococcus aureus
• Group A beta-haemolytic streptococci (picture )
• Eczema (picture ) may predispose the skin to impetigo.
• The infection usually spreads by autoinoculation.
• Recurrences are often caused by bacteria remaining in the nostrils from where they are re-spread by fingering of the nose.

Treatment

• Treatment is started on the basis of the clinical presentation.
• If the disease is confined to a small area the treatment consists of soaking the crusts so that they are detached, and applying an antimicrobial ointment (fusidic acid Interventions for Impetigo or a combination of neomycin and bacitracin).
• If the disease is more widespread (> 6 cm² ) use a systemic antimicrobial effective against S. aureus, primarily cephalexin Systemic Antibiotics in the Treatment of Impetigo in Children or flucloxacillin 750-1 000 mg 3 times daily. Duration of treatment is usually 7-10 days. Patients with cephalosporin allergy can be treated with clindamycin.
• If the patient has eczema a topical preparation containing a glucocorticoid and an antimicrobial agent should be used together with systemic antimicrobials until the skin is intact.
• Do not forget further treatment of the eczema.
• The most common reasons for poor response to treatment
  • The diagnosis is incorrect. The patient has scabies, lice, or ringworm.
  • The crusts have not been soaked and removed. The bacteria can survive under crusts.
  • The underlying eczema has not been treated.
  • The nostrils serve as reservoir for bacteria (apply neomycin-bacitracin or fusidic acid ointment into the nostrils. Mupirocin should not be used for this disease as its use should be limited to the eradication of methicillin-resistant Staphylococcus aureus).

Pictures