Page 21 - LECTURE NOTES

3.6. Bacterial infection of the skin (pyodermas)

Bacterial skin infection is one of the commonly encountered problems in the tropics.
When the normal protective functions of the skin are altered by trauma (scratching and

excoriation ), pre existing and/or coexisting skin diseases like, eczema, scabies or
venous or lymphatic insufficiency, pathogenic organisms get access to the skin to

establish infection.

3.6.1 Impetigo

Impetigo is a contagious superficial (stratum corneum) pyogenic infection of the skin.
Two main clinical forms are recognized: non-bullous impetigo (or impetigo contagiosa)

and bullous impetigo.
Impetigo presents as either a primary pyodermal of intact skin or a secondary infection

due to preexisting skin disease or traumatized skin. Impetigo rarely progresses to
systemic infection, although post streptococcal glomerulonephritis may occur as a rare

systemic complication.

Impetigo occurs in individuals of all ages. However, children younger than 6 years
have a higher incidence of impetigo than adults.

Bullous impetigo is most common in neonates and infants

Causative agents

It is caused by Staphylococcus aureus.
The non-bullous form is usually caused by group Aβ streptococcus, in some

geographical areas Staphylococcus aureus or by both organisms together.

Clinical features

Non-bullous impetigo:
The characteristic lesion is a fragile vesicle or pustule that readily ruptures and

becomes a honey-yellow, adherent, crusted papule or plaque and with minimal or no

surrounding redness and usually occurs on hands and face. unless secondary
infection exists (cellulites).

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