2.2.2 Impetigo Contagiosa

Grading & Level of Importance: A




Superficial pyoderma.


Worldwide distribution, infants and small children mostly affected.


Superficial cutaneous bacterial infection of the interfollicular epidermis, more common in children, those with atopic dermatitis, and in warm, moist environments.

Aetiology & Pathogenesis

Staphyloccal and streptococcal bacterial infection spread by fomites or direct contact, usually to predisposed skin (sometimes disturbed epidermal barrier; under or over-washing of children`s skin; reduced local immune function in atopic dermatitis, angular stomatitis, rhinitis, herpes simplex, pruritus with scratching). Reservoir: nose. Causative agent usually 80% staphylococci, 10 % ß-hemolytic streptococci and 10% mixed infections.

Signs & Symptoms

Erythema, pustules, erosions and bullae, honey-yellow crusts.


Often face but can be anywhere.


Two types: a) small bullous and large bullous (10-20%). b) non-bullous (80-90%). Streptogenic are more crusted and red/inflammatory, staphylogenic more honey-like yellowish with small and large blisters. In addition, a S.pyogenes related deep penetrating ecthyma type.

Laboratory & other workups

In widespread streptogenic type, differential blood count, CRP, urine for exclusion of glomerulonephritis and, in large bullous staphylogenic types, additionally exfoliatin toxin A/B. 


Neutrophilic pustule within the stratum corneum in small bullous type, in large bullous type mid epidermis with little abscesses.


Usually self-limited, no scarring. Flat, then tiny vesicles followed by blisters, serocrusts and finally desquamation. Scratching leads to new lesions by autoinoculation.


Acute glomerulonephritis when infection is caused by certain strains of streptococci. Heavy producers of toxins can lead to TSS and SSSS.


Clinical features, Gram stain, culture.

Differential diagnosis

Herpes simplex, eczema herpeticum, superficial folliculitis. Other skin diseases in particular eczemas with impetiginization.

Prevention & Therapy

  • Topical: antiseptics; fusidic acid;, wet-dry dressings if crusted.
  • Systemic: in widespread streptococcal and staphylococcal types penicillinase resistant antibiotics types, erythromycin, culture-directed secondary antibiotics.
  • MRSA carriers in the nostrils : mupirocin
  • Contact tracing



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