About Impetigo

Impetigo is a superficial infection of the skin, usually by the gram positive bacteria S. aureus, that most often occurs in children. The basic lesion is a pustule, which ruptures to form the classic “honey colored crust”; often, intact pustules cannot be found. Removal of the crust reveals a glistening base, but not ulceration. Lesions can be located anywhere but favor the face. It can occur secondary to other skin diseases, such as atopic dermatitis.

With what can impetigo confused?

Group A streptococci infection can cause ecthyma, which is a deeper infection than impetigo that also presents as a crust; removal of the crust reveals an ulcer. Streptococci infection also usually causes surrounding erythema, which is not the case for impetigo. Streptococci infection is more often found on the lower extremities than on the face. After the vesicles of herpes simplex virus crust over, they can be mistaken for impetigo. Fungal infections can sometimes cause pustules.

How is impetigo diagnosed?

Impetigo is usually diagnosed clinically. Gram stain and bacterial cultures will reveal the causative gram positive S. aureus (The crust must be removed before obtaining a specimen for analysis.)

How is impetigo treated?

Topical antibiotics such as bacitraicin and mupirocin (Bactroban) are often used for confined lesions. For larger or multiple lesions, a penicillinase-resistant penicillin such as dicloxacillin or a first generation cephalosporin such as cephalexin are preferred.

What is the prognosis for impetigo?

With treatment, lesions resolve within several days without complications. Infection with certain strains of S. aureus give rise to bullous impetigo.

More on impetigo

Image links Many impetigo image links

Other useful links

KidsHealth: Impetigo

Park, R. Impetigo. e-medicine. February 27, 2006

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