What is impetigo? |

Causes and Symptoms

Impetigo is a superficial bacterial skin

infection
usually caused by group A streptococcus, Staphylococcus aureus, or a mixture of both. Group A streptococcus
was originally the predominant pathogen, but recently S. aureus has become the most common strain. Impetigo caused by either of these bacteria is clinically identical.

Children are most commonly affected by impetigo, and infection is often preceded by minor trauma such as insect bites. Outbreaks predominantly occur during the summer months when the climate is hot and humid. Impetigo is very contagious and easily spread in crowded conditions such as in families, schools, the military, and athletics. Poverty and poor personal hygiene can also predispose individuals to infection.

A typical infection first develops as multiple vesicopustules, which rupture and form a characteristic golden yellow crust. The lesions are painless but commonly pruritic (itchy), and scratching can serve to spread infection. Systemic symptoms are rare, but there can be local lymphadenopathy. The face, particularly the region around the mouth, is a common site of infection.

Treatment and Therapy

Topical and oral antibiotics have been used for the treatment of impetigo. Historically, the treatment of choice was penicillin or ampicillin. This has changed, however, as the most predominant bacteria are now S. aureus instead of group A streptococcus, which almost universally produces a beta-lactamase that makes them resistant to penicillin. It is now recommended to use a beta-lactamase-resistant penicillin such as dicloxacillin or a first-generation cephalosporin such as cephalexin. Erythromycin can be used if the patient is allergic to penicillin.

Topical antibiotics such as mupirocin and fusidic acid (not available in the United States) are very effective treatments. Mupirocin has been shown to be as effective as erythromycin. Topical antibiotics are used with mild or moderate cases; and oral antibiotics are reserved for more advanced cases. Topical antibiotics are as effective and have fewer side effects, which make them a better choice in less severe cases. A ten-day course is recommended whether oral or topical antibiotics are used.

Gentle cleansing of the area with soap and water can be helpful. Personal hygiene may be discussed with the patient to help prevent recurrence of infection. Frequent hand washing and not sharing bath linens can help prevent spread of the bacteria. The lesions usually heal without scarring.

Bibliography

Bhumbra, Nasreen A., and Sophia G. McCullough. “Skin and Subcutaneous Infections.” In Update on Infectious Diseases, edited by Richard I. Haddy and Karen W. Krigger. Philadelphia: W. B. Saunders, 2003.

"Impetigo." Mayo Clinic, May 15, 2013.

Larsen, Laura, ed. Childhood Diseases and Disorders Sourcebook. Detroit, Mich.: Omnigraphics, 2012.

Plaza, Jose A., and Victor G. Prieto. Inflammatory Skin Disorders. New York: Demos Medical Publishing, 2012.

Scholten, Amy. "Impetigo." Health Library, September 9, 2012.

Swartz, Morton N., and Mark S. Pasternack. “Cellulitis and Subcutaneous Tissue Infection.” In Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases, edited by Gerald L. Mandell, John E. Bennett, and Raphael Dolin. 7th ed. New York: Churchill Livingstone/Elsevier, 2010.

Taylor, Julie Scott. “Interventions for Impetigo.” American Family Physician 70, 9. (November 1, 2004).

Van Schoor, Jacky. "Superficial Skin Infections in the Pharmacy." SAPA 13, 1. (2013): 39–40.

Zappi, Eduardo. Dermatopathology: Classification of Cutaneous Lesions. New York: Springer, 2013.