Core Dermatology Diagnoses / CategoriesInfectious

Impetigo

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Publish date: Posted on
Last updated: February 17, 2024

Keywords #

impetigo
staphylococcus aureus
streptococcus pyogenes
MRSA
skin infection
antibiotic resistance
topical antibiotic 

Diagnosis #

Impetigo is a common bacterial skin infection.[1,2] There are non-bullous (70%) and bullous (30%) forms: Staphylococcus aureus (S. aureus) and Streptococcus pyogenes (S. pyogenes) are the typical organisms in non-bullous impetigo while bullous impetigo is almost exclusively S. aureus.[1-3] Bacterial colonization of the nasopharynx, axillae, and perineal areas in those who have breaks in previously healthy skin is believed to cause clinical disease.[2]

Key Concepts #
  • Impetigo is the most common bacterial skin infection among children 2-5 years old.
  • Skin trauma, bug bites, and eczema make otherwise healthy skin susceptible.
  • The fluid inside skin lesions is highly contagious.
  • Topical antibiotics are best for localized infection; systemic antibiotics should be reserved for extensive or unresponsive infections.
  • Due to antibiotic resistance, topical antibiotics should not be used on uninfected skin.
Epidemiology #

Impetigo affects 1% of children worldwide, most commonly ages 2-10.[3] Prevalence is increased in tropical and urban areas where overcrowding and poor hygiene promote spread via direct contact.[1-3] Primary infection of intact skin can happen, but more commonly insect bites, eczema, and other sources of trauma compromise the cutaneous barrier and cause secondary impetigo.[2,3]

Clinical Features #
  • In non-bullous impetigo, fragile vesicles generally on the face and extremities easily rupture and leave superficial erosions with the classic honey-colored crusts.2,4 The crusts may be pruritic or painful.
  • In bullous impetigo, large fluid-filled bullae on the trunk and intertriginous areas rupture leaving a brown collarette of scale.[2] The blisters are highly contagious, and satellite lesions may occur with picking and scratching.[1]
  • In both variants, systemic symptoms are uncommon but may include fever, weakness, and diarrhea.[2]
  • Complications include cellulitis, septicemia, osteomyelitis, guttate psoriasis, Staphylococcal scalded skin syndrome, and, rarely, post-streptococcal glomerulonephritis.[2]
Differential Diagnoses #
Diagnostic Workup #

Diagnosis is made clinically. Swabbing of infected skin or blister fluid can help confirm diagnosis, determine the causative micro-organism and help guide treatment.

Treatment #

Impetigo is generally a self-limiting condition that resolves without scarring in 3-4 weeks.[1] Uncomplicated, localized impetigo can be treated with a 5-7 day course of topical antibiotic such as mupirocin or retapamulin.[1,2,4] These topicals should only be used on infected areas to prevent the development of resistant organisms.[4]

Severe, generalized impetigo with systemic symptoms or failure of topical therapy requires systemic antibiotic treatment.[1,2] Resistant organisms are on the rise and complicate the treatment process. If MRSA is suspected, treatment with trimethoprim/sulfamethoxazole, clindamycin, or a tetracycline is recommended.[2] Penicillin and macrolides are no longer recommended.[1,2]

Slide Viewer #
https://utahderm.med.utah.edu/image-viewer/
References #
  1. D’Cunha NM, Peterson GM, Baby KE, Thomas J. Impetigo: A need for new therapies in a world of increasing antimicrobial resistance. J Clin Pharm Ther. 2018;43(1):150-153.
  2. Hartman-Adams H, Banvard C, Juckett G. Impetigo: diagnosis and treatment. Am Fam Physician. 2014;90(4):229-235.
  3. Oranje AP, de Waard-van der Spek FB. Recent developments in the management of common childhood skin infections. J Infect. 2015;71 Suppl 1:S76-79.
  4. Kosar L, Laubscher T. Management of impetigo and cellulitis: Simple considerations for promoting appropriate antibiotic use in skin infections. Can Fam Physician. 2017;63(8):615-618.
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