Impetigo is a superficial skin infection of the epidermis primarily by caused by S. aureus or strep. pyogenes. It is highly contagious.
🦠 Pathophysiology and causative organisms
It occurs when bacteria enter through a break in the skin or it may occurs a complication of eczema or dermatitis. It has an incubation period of 4-10 days
It is caused by either staphylococcus aureus or streptococcus pyogenes. They release serine proteases which break the bonds that hold epidermal cells together. This allows the bacteria to spread under the stratum corneum of the epidermis and splits the stratum corneum from the stratum granulosum → blistering.
Spread occurs by direct contact but indirect spread may occur via fomites.
😷+ 🔢 Presentation and classification
Lesions may occur anywhere, but most typically on face, flexures and limbs that are not covered by clothing.
It is most common in school children.
It can be classified as either bullous or non-bullous:
→ Bullous impetigo
Usually caused by s. aureus.
- Bullae - these are fluid-filled vesicles usually 1-2cm in diameter.
- Golden crust - the bullae rupture to form these crusts that usually disappears in 2-3 weeks without scarring.
- Pruritic rash
- Fever - not always febrile but more likely in bullous impetigo.
→ Non-bullous impetigo
- Pruritic rash
- Exudate - thin walled vesicles rupture quickly and release the exudate which forms the golden crust which also heals in 2-3 weeks without scarring.
🔍 Investigations
- It is usually a clinical diagnosis.
- Swabs may be taken for cultures in persistent cases as we have to consider MRSA infection.
🧰 Management
Localised non-bullous impetigo
- 🥇 Hydrogen peroxide 1% cream - applied 2-3x daily for 5 days.
If not suitable, a short-course topical antibiotic can be considered:
- 🥈 Fusidic acid 2% cream - applied 3x daily for 5 days.
- 🥈 Mupirocin 2% cream - if fusidic acid resistance may be present. Should also be used with MRSA.
Widespread non-bullous impetigo or bullous impetigo
- 🥇 Oral flucloxacillin
- 🥇 Oral clraithromycin/erythromycin - if patient has penicillin allergy.