Impetigo

Key Features

Essentials of Diagnosis

• Superficial blisters filled with purulent material that rupture easily

• Crusted superficial erosions

• Positive Gram stain and bacterial culture

General Considerations

• A contagious and autoinoculable infection of the skin caused by staphylococci or rarely streptococci

• In temperate climates, most cases are associated with Staphylococcus aureus infection

• Streptococcus species are more common in tropical climates

Clinical Findings

Symptoms and Signs

• The lesions consist of macules, vesicles, bullae, pustules, and honey-colored gummy crusts that when removed leave denuded red areas

• The face and other exposed parts are most often affected

• Ecthyma is a deeper form of impetigo caused by staphylococci or streptococci, with ulceration and scarring; it occurs frequently on the extremities

Differential Diagnosis

• Contact dermatitis (acute)

• Herpex simplex

Diagnosis

• Gram stain and culture confirm the diagnosis

Treatment

• Soaks and scrubbing can be beneficial, especially in unroofing lakes of pus under thick crusts

• Topical agents such as bacitracin 500 units/g applied twice daily, mupirocin 2% ointment applied three times daily, or retapamulin 1% ointment applied twice daily can be attempted for 5–14 days for infections limited to small areas

• Cephalexin, 250 mg four times daily orally

• Doxycycline, 100 mg twice daily orally, or trimethoprim-sulfamethoxazole, double-strength twice daily orally, can be used for penicillin allergy and methicillin-resistant S aureus

• Recurrent impetigo, which is due to nasal carriage of S aureus, is treated with rifampin, 300 mg orally twice daily, or mupirocin intranasal ointment applied intranasally twice daily for 14 days

• Bleach baths (1/4 to 1/2 cup per 20 L of bathwater for 15 minutes 3–5 times weekly) for all family members may help reduce the spread

Outcome

Prevention

• Individuals should not share towels if there is a case of impetigo in the household

References