Impetigo

Impetigo is a benign, contagious infection of the epidermis due to group A ß-haemolytic streptococcus and Staphylococcus aureus. Co-infection is common. Transmission is by direct contact. Lack of water, and poor hygiene, increase spread.

Primary infections are most common in children. Secondary infections complicating preexisting pruritic dermatoses (lice, scabies, eczema, herpes, chickenpox, etc.) are more common in adults.

Clinical features

• Non bullous impetigo (classic form): flaccid vesicle on erythematous skin which becomes pustular and forms a yellowish crust. Different stages o the infection may be present simultaneously. The lesion does not leave a scar. The most common sites of infection are around the nose and mouth, on the limbs or on the scalp.
• Bullous impetigo: large flaccid bullae and erosions of the skin in the ano-genital region in newborns and infants.
• Ecthyma: an ulcerative form of impetigo that leaves scars. This form is most common in the immunocompromised (e.g. HIV infection, malnutrition), diabetics and alcoholics.
• Regardless of the type of impetigo: absence of fever or systemic signs.
• Possible complications:
  • abscess, pyodermitis, cellulitis, lymphangitis, osteomyelitis, septicaemia;
  • acute glomerulonephritis (routinely look for signs of glomerulonephritis).

Treatment

• Localised non bullous impetigo (max. 5 lesions in a single skin area):
  • Clean with soap and water and dry before applying mupirocin.
  • 2% mupirocin ointment: one application 3 times daily for 7 days. Reassess after 3 days. If there is no response, switch to oral antibiotic therapy (see below).
  • Keep fingernails short. Avoid touching the lesions, keep them covered with gauze if possible.

• Extensive non bullous impetigo (more than 5 lesions or impetigo involving more than one skin area), bullous impetigo, ecthyma, impetigo with abscess; immunocompromised patient; topical treatment failure:
  • Clean with soap and water and dry 2 to 3 times daily.
  • Keep fingernails short. Avoid touching the lesions, keep them covered with gauze if possible.
  • Incise abscesses if present.
  • Administer oral antibiotic therapy a Citation a. In penicillin-allergic patients only (resistance to macrolides is common), azithromycin PO for 3 days (children: 10 mg/kg once daily; adults: 500 mg once daily). : 
    cefalexin PO for 7 days
    Neonates under 7 days: 25 mg/kg 2 times daily
    Neonates 7 to 28 days: 25 mg/kg 3 times daily
    Children 1 month to 12 years: 25 mg/kg 2 times daily
    Children 12 years and over and adults: 1 g 2 times daily
    or
    cloxacillin PO for 7 days
    Children over 10 years: 15 mg/kg 3 times daily (max. 3 g daily)
    Adults: 1 g 3 times daily
    Note: in newborns with lesions located around the umbilicus, administer cloxacilllin IV.

• For all patients:
  • Quarantine from school (children can return to school after 24 to 48 hours of antibiotic therapy).
  • Look for and treat any underlying dermatosis: lice, scabies, eczema, herpes, scalp ringworm, or an ENT infection.
  • Trace and treat contacts.
  • Check for proteinuria (use urine dipstick) 3 weeks after the infection.