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 therapy1 :
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: licescabieseczemaherpesscalp ringworm, or an ENT infection.
• Trace and treat contacts.
• Check for proteinuria (use urine dipstick) 3 weeks after the infection.



Footnotes
Ref Notes
1 In penicillin-allergic patients only (résistance to macrolides is common), azithromycin PO for 3 days (children: 10 mg/kg once daily; adults: 500 mg once daily).