Impetigo

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Impetigo is a blistering skin infection and is usually caused by Staphylococcus. aureus or Streptococcus pyogenes.

What does the rash look like?

The impetigo rash can either be bullous (with bullae or fluid-filled lesion larger than 0.5cm) or non-bullous (much more common). In the non-bullous form, there are vesicles. Often there is golden crusting on top the of rash.

Golden crusting

What are the other symptoms?

The rash can be itchy or painful (but not commonly). In severe disease, it can be associated with pyrexia and lymphadenopathy.

How is it diagnosed?

Impetigo is usually diagnosed clinically, but if the infection is severe then bacterial swabs could be sent. Resistant infection may be caused by MRSA so a swab would be helpful in this case too.

What is the course of the illness?

As the impetigo resolves, the golden crust dries and separates.

What are the possible complications?

Impetigo can spread very easily on contact and often spreads to other sites on the body.

Cellulitis, osteomyelitis or sepsis can occur, but more commonly in neonates with bullous impetigo.

Post-streptococcal glomerulonephritis is also seen.

How long are patients infectious for?

Patients are infectious until the crusting has all dried up. They should stay away from childcare until then.

What treatment should I offer?

Treatment is with antibiotics and depends on the extensiveness and resistance of the infection.

Impetigo with localized, superficial infection

These children are usually managed with topical antibiotics (mupirocin 2% TDS or fusidic acid 2% TDS) for 5-7 days, which has shown to be as effective as oral antibiotics.

In neonates, even a localized superficial infection should be treated with oral antibiotics (erythromycin for 7 days) and a dermatologist consulted.

 

Widespread, cutaneous impetigo

This should be treated with one of the following oral antibiotics for 7 days.

  • Flucloxacillin: 12.5-25 mg/kg QID; adult dose is 250-500mg QID
  • Erythromycin: 10mg/kg QID; adult dose is 250mg QID
  • Cephalexin: 25mg/kg QID; adult dose is 250-500mg QID

 

Localized, superficial impetigo with suspected MRSA infection

If the infection is resistant to the treatment above, or MRSA is suspected then treatment should be with one of the following antibiotics:

  • Clindamycin: 5mg/kg QID; dose in adults is 150-450mg QID
  • Trimethoprim/sulfamethoxazole: 4-5mg/kg BD; adult dose is 160mg BD (dose refers to trimethoprim component)

 

Impetigo with a deep infection or haematogenous spread

IV antibiotics are indicated in children with pyrexia or systemic symptoms. Use one of the following antibiotics.

  • Flucloxacillin: 50mg/kg QID IV (max 2g)

 

Impetigo with a deep infection or haematogenous spread and suspected MRSA

These patients should be treated with vancomycin.

  • Vancomycin: 10mg/kg IV QID; adult dose is 500mg IV QID or 1g IV BD

 

Recurrent impetigo

In patients with recurrent infections consider intranasal antibiotics (mupirocin 2% TDS for 7 days) to treat nasal colonization.

 

Skin hygiene

Washing with soap and water twice a day is recommended to reduce skin bacteria.

 

References

Freeman M, Del Mar C. Impetigo. Best Practice, BMJ

McLinn S. A bacteriologically controlled, randomized study comparing the efficacy of 2% mupirocin ointment (Bactroban) with oral erythromycin in the treatment of patients with impetigo. J Am Acad Dermatol. 1990;22:883-885.

About the authors

  • Tessa Davis is a Consultant in Paediatric Emergency Medicine at the Royal London Hospital and a Senior Lecturer at Queen Mary University of London.

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