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AlexanderSalava

Impetigo

Essentials

  • Impetigo is a common, superficial skin infection most often caused by Staphylococcus aureus bacteria.
  • The symptoms are usually mild.
  • Impetigo spreads easily within families, day-care centres and schools.
  • It may appear as a primary infection on healthy skin or secondary to another skin problem (such as eczema, scabies, lice).
  • Based on its severity, it can be treated by either topical or systemic antimicrobial treatment or both.

Clinical features

  • Children are most commonly affected. The skin lesions typically cause few symptoms (no itching or pain); there are no systemic symptoms or fever.
  • The disease spreads through contact with various skin areas and from person to person.
  • It is clinically divided into non-bullous (more common) and bullous types.
    • The non-bullous type typically causes clearly defined, erythematous spots covered with honey-coloured crusts.
    • As the crusts detach, clearly defined, weeping erosive surfaces remain, possibly with collarrettes of scales (pictures 1 2).
    • In the bullous type of disease, there are vesicles containing clear fluid on erythematous skin. After the blisters burst, wound surfaces surrounded by collarrettes of scales remain (picture 3).
    • Both types of disease typically occur around the nostrils and the mouth, on the face and skin folds (pictures 4 5 6 7).
  • Staphylococcus aureus is the most common pathogen involved. Infections caused by beta-haemolytic streptococci (Streptococcus pyogenes) are seen more rarely, and the clinical picture is in such cases usually more severe (more blister formation, rapid spread and inflammatory activity; picture 8).
  • Glomerulonephritis may develop as a rare complication of disease caused by beta-haemolytic streptococci. Nephritic disease typically appears about 6 weeks after the skin infection.

Diagnosis

  • The diagnosis is usually clinical, and no further investigations are needed.
  • Remember to ensure a good clinical examination and thorough history taking.
    • Is there anything suggesting an underlying skin problem (scabies, lice, eczema)?
  • If bacterial culture is done, it usually grows S. aureus.
  • If response to treatment is poor and in high-risk patients (travel, previously detected resistance), methicillin-resistant S. aureus (MRSA) should be excluded by bacterial culture.
  • In case of recurrent infection, colonization with S. aureus can also often be detected by bacterial culture of samples taken from the nostrils, and a PVL (Panton-Valentine leukocidin) exotoxin-producing strain often from the skin.
  • Samples for exclusive differential diagnosis for fungal testing (fungal culture) and testing for herpes (nucleic acid detection) should be taken as necessary.

Differential diagnosis

  • Eczematous diseases
    • There may be secondary infection, particularly of atopic eczema with itching as its main symptom; picture 9.
  • Herpes simplex (usually tingling and pain) Herpes Simplex Infection of the Skin
  • Ringworm (usually on the legs, circular scaling lesions) Dermatomycoses
  • Scabies Scabies
    • Impetigo may appear as a secondary disease in patients with scabies; this is called scabies surrepticius. The possibility of scabies should be kept in mind particularly in adult patients with impetigo.

Treatment

  • Treatment should be provided depending on how serious the clinical condition is (spread, symptoms, cases in close contacts, previous treatment). Cases resistant to treatment usually require systemic medication.
  • If the disease is confined to a small area, it is often sufficient to soak the crusts (using a washcloth to actually detach them!) and apply an antimicrobial ointment (fusidic acid Interventions for Impetigo or a combination of neomycin and bacitracin) over a course of 1-2 weeks.
  • If the disease is more widespread or causes more severe symptoms, use a systemic antimicrobial effective against S. aureus, primarily flucloxacillin 750-1 000 mg 3 times daily or cephalexin 500-750 mg 3 times daily, in addition to topical treatment.
    • Dosage in children
      • Cephalexin 25-50 mg/kg daily divided into 2-3 doses
      • Flucloxacillin (only in tablet form, not for children weighing less than 40 kg) 30-50 mg/kg daily divided into 3 doses
  • The duration of treatment is usually 7-10 days. Patients with cephalosporin allergy can be treated with clindamycin or macrolides.
  • If eczema is clearly involved, a topical preparation containing a glucocorticoid and an antimicrobial agent should be used together with systemic antimicrobials until the skin is intact.
  • In a patient with eczema, do not forget further treatment of the eczema.
  • The most common reasons for poor response to treatment
    • The diagnosis is incorrect. The patient has scabies, head lice, or ringworm.
    • The crusts have not been soaked and removed. The bacteria can survive under crusts.
    • The underlying eczema has not been treated, and the skin is constantly broken.
  • In recurring impetigo, colonization of the nostrils may be the underlying cause; this should be treated by topical antimicrobials (such as fusidic acid or mupirocin).
  • The infection may also recur through domestic animals or hygiene products (such as towels) of close contacts. If so, the patient's and close contacts' hygiene products should be replaced, linen washed and more intensive hand hygiene practised.

    References

    • Hall LM, GorgWang H, Bai Z, Shen C, et al. The global, regional, and national patterns of change in the burden of bacterial pyoderma from 1990 to 2019 and the forecast for the next decade. Sci Rep 2025;15(1):1810. [PubMed]
    • Vendrik KEW, Kuijper EJ, Dimmendaal M, et al. An unusual outbreak in the Netherlands: community-onset impetigo caused by a meticillin-resistant Staphylococcus aureus with additional resistance to fusidic acid, June 2018 to January 2020. Euro Surveill 2022;27(49): [PubMed]
    • Hall LM, Gorges HJ, van Driel M, et al. International comparison of guidelines for management of impetigo: a systematic review. Fam Pract 2022;39(1):150-158. [PubMed]
    • Gahlawat G, Tesfaye W, Bushell M, et al. Emerging Treatment Strategies for Impetigo in Endemic and Nonendemic Settings: A Systematic Review. Clin Ther 2021;43(6):986-1006. [PubMed]
    • Schachner LA, Lynde CW, Kircik LH, et al. Treatment of Impetigo and Antimicrobial Resistance. J Drugs Dermatol 2021;20(4):366-372. [PubMed]
    • Johnson MK. Impetigo. Adv Emerg Nurs J 2020;42(4):262-269. [PubMed]
    • Hartman-Adams H, Banvard C, Juckett G. Impetigo: diagnosis and treatment. Am Fam Physician 2014;90(4):229-35. [PubMed]
    • Koning S, van der Sande R, Verhagen AP, et al. Interventions for impetigo. Cochrane Database Syst Rev 2012;1(1):CD003261. [PubMed]