Impetigo

Impetigo

Impetigo is a highly contagious superficial bacterial infection of the skin involving the stratum corneum of the epidermis. It is particularly common among children and people living in disadvantaged or resource-limited settings. Small family, daycare, or school outbreaks are common.

Transmission occurs through:

• Direct skin-to-skin contact.

• Contact with contaminated objects such as towels, clothes, and bedding.

• Self-inoculation from scratching infected lesions.

Etiology

The most common causative organisms are:

• Staphylococcus aureus

• Streptococcus pyogenes (Group A Streptococcus)

Types include:

• Non-bullous impetigo (most common, approximately 70% of cases).

• Bullous impetigo caused by toxin-producing Staphylococcus aureus.

Risk factors

• Poor personal hygiene.

• Crowded living conditions.

• Malnutrition.

• Warm, humid climate.

• Minor skin trauma such as scratches, insect bites, scabies, or eczema.

• Nasal carriage of Staphylococcus aureus.

• Immunocompromised states.

Clinical presentation

• Polycyclic vesicles or blisters, which may contain pus.

• Fragile vesicles that rupture easily.

• Early lesions are isolated or confluent erosions.

• Yellowish ("honey-colored") crusts.

• Mild itching (common).

• Usually painless.

Severe cases may present with:

• Fever (pyrexia).

• Enlarged lymph nodes.

• Malaise.

Diagnosis

Diagnosis is usually clinical and is based on:

• Polycyclic vesicles or pustules.

• Superficial erosions.

• Honey-colored crusts.

• Typical distribution around the mouth and nose in children.

Investigations

Investigations are not required in typical uncomplicated cases.

Consider investigations in:

• Recurrent infections.

• Failure to respond to treatment.

• Suspected methicillin-resistant Staphylococcus aureus (MRSA).

• Outbreak investigations.

Possible investigations include:

• Bacterial swab for culture and sensitivity.

• Blood glucose testing in recurrent infections.

• HIV testing in persistent or recurrent cases where clinically indicated.

Management

Non-pharmacological treatment

• Improve personal hygiene.

• Frequent hand washing.

• Wash lesions gently with soap and clean water.

• Remove crusts before applying topical medication.

• Keep fingernails short.

• Avoid sharing towels, clothing, and bedding.

• Exclude affected children from school or daycare until 24 hours after starting antibiotic therapy.

Pharmacological treatment

• Wash lesions with soap and water.

• Remove crusts.

Potassium permanganate (PP) wet dressing

• 1:40,000 (0.025%) solution.

• Apply every 12 hours.

• Duration: 3–4 days.

• Each session should last 15–20 minutes.

Gentian violet paint (topical) 0.5%

• Apply every 12 hours for 5 days.

OR

Mupirocin (topical) 2%

• Apply every 12 hours for 5–7 days.

OR

Fusidic acid (topical)

• Apply every 12 hours for 5–7 days.

Systemic antibiotics

Add an oral antibiotic if severe disease or systemic symptoms (e.g. pyrexia) are present, or if there are extensive lesions, lymphadenopathy, recurrent infection, failure of topical therapy, or outbreak control is required.

Phenoxymethylpenicillin (PO)

• Adults: 500 mg every 6 hours for 7 days.

• Children: 25 mg/kg every 6 hours for 7 days.

OR

Erythromycin (PO)

• Adults: 500 mg every 8 hours for 10 days.

• Children: 25–50 mg/kg every 8 hours for 10 days.

OR

Amoxicillin + clavulanic acid (PO)

• 625 mg every 8 hours for 5 days.

Complications

Although usually mild, untreated impetigo may lead to:

• Cellulitis.

• Abscess formation.

• Lymphangitis.

• Acute post-streptococcal glomerulonephritis.

• Rarely, acute rheumatic fever.

Prevention

• Early diagnosis and treatment of infected individuals.

• Maintain good personal hygiene and daily bathing with soap.

• Practice regular hand hygiene.

• Avoid scratching insect bites and skin lesions.

• Treat underlying skin conditions such as eczema and scabies.

• Avoid sharing towels, clothing, toys, and bedding.

• Exclude infected children from school or daycare until 24 hours after antibiotic treatment has started.

• In recurrent household outbreaks, consider screening and treating nasal carriers of Staphylococcus aureus where appropriate.