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New Treatments for Impetigo

Impetigo is a common, contagious, superficial skin infection that is produced by streptococci, staphylococci, or a combination of both bacteria. There are two different clinical presentations: bullous impetigo and nonbullous impetigo. Both begin as vesicles with a very thin, fragile roof consisting only of stratum corneum. Bullous impetigo is primarily a staphylococcal disease. Nonbullous impetigo was once thought to be primarily a streptococcal disease, but staphylococci are isolated from the majority of lesions in both bullous and nonbullous impetigo. S. aureus is now known to be the primary pathogen in both bullous and nonbullous impetigo.

Children in close physical contact with each other have a higher rate of infection than do adults. Symptoms of itching and soreness are mild; systemic symptoms are infrequent. Impetigo may occur after a minor skin injury such as an insect bite, but it most frequently develops on apparently unimpaired skin. The disease is self-limiting, but when untreated it may last for weeks or months. Poststreptococcal glomerulonephritis may follow impetigo.

Bullous impetigo

Bullous impetigo (staphylococcal impetigo) is caused by an epidermolytic toxin produced at the site of infection, most commonly by staphylococci of phage Group II.

Clinical manifestations.

Bullous impetigo is most common in infants and children but may occur in adults. It typically occurs on the face, but it may infect any body surface. There may be a few lesions localized in one area, or the lesions may be so numerous and widely scattered that they resemble poison ivy. One or more vesicles enlarge rapidly to form bullae in which the contents turn from clear to cloudy.

Nonbullous impetigo

Nonbullous impetigo originates as a small vesicle or pustule that ruptures to expose a red, moist base. A honey yellow to white-brown, firmly adherent crust accumulates
as the lesion extends radially. There is little surrounding erythema. Satellite lesions appear beyond the periphery. The lesions are generally asymptomatic. The skin around the nose and mouth and the limbs are the sites most commonly affected. The palms and soles are not affected.

Intact skin is resistant to colonization or infection with group A beta-hemolytic streptococci, but skin injury by insect bites, abrasions, lacerations, and burns allows the streptococci to invade. A pure culture of group A beta-hemolytic streptococci may sometimes be isolated from early lesions.

Acute nephritis

Acute nephritis tends to occur when many individuals in a family have impetigo. Most cases occur in the southern part of the United States. Infants under 1˝years of age are rarely affected by nephritis following impetigo. The highest incidence of nephritis following impetigo is in children.

Prevention of impetigo

Mupirocin (Bactroban) or Triple antibiotic ointment, containing bacitracin, polysporin, and neomycin, applied three times daily to sites of minor skin trauma (e.g., mosquito bites and abrasions).

Recurrent impetigo

Patients with recurrent impetigo should be evaluated for carriage of S. aureus. The nares are the most common sites of carriage, but the perineum, axillae, and toe webs may also be colonized. Mupirocin ointment (Bactroban).

Treatment of impetigo

Impetigo may resolve spontaneously or become chronic and widespread. Studies show that 2% mupirocin ointment is as safe and effective as oral erythromycin in the treatment of patients.

Oral antibiotics.

Because some cases of impetigo have a mixed infection of staphylococci and streptococci, penicillin is inadequate for treatment. A 5- to 10-day course.

Mupirocin (Bactroban).

Mupirocin ointment is the first topical antibiotic approved for the treatment of impetigo. It is active against staphylococci (including methicillin-resistant strains) and streptococci.