Impetigo

Impetigo is a superficial bacterial skin infection caused predominantly by Staphylococcus aureus and group A Streptococcus.

Non bullous impetigo is the commonest form. Bullous impetigo is caused by toxin producing S. aureus.

Non bullous disease produces:

• Vesicles or pustules that rupture
• Characteristic honey coloured crusts
• Mild surrounding erythema
• Lesions commonly around the nose and mouth or on exposed limbs

Bullous disease produces fragile superficial bullae that rupture to leave moist erythematous bases.

Systemic illness is uncommon in localized disease.

Diagnosis is clinical.

Swab lesions when:

• Infection is recurrent
• MRSA is suspected
• Disease is widespread
• Initial treatment fails

For localized uncomplicated non bullous impetigo:

• A topical antiseptic can be considered where available.

• If topical antibiotic treatment is required, fusidic acid 2% cream three times daily for 5 days is a commonly used regimen where local resistance remains acceptable.

For widespread, bullous or systemically significant disease:

• Flucloxacillin PO for 5 days is first line where methicillin sensitive S. aureus is expected.

Age based dosing commonly used includes:

• 1 month to 1 year: 62.5 to 125 mg four times daily
• 2 to 9 years: 125 to 250 mg four times daily
• 10 to 17 years: 250 to 500 mg four times daily

A 5 day course is generally sufficient, extending to 7 days when response is slower or disease is extensive.

For true penicillin allergy, use an appropriate macrolide or alternative according to local susceptibility.