Diagnosis and Treatment of Impetigo
University of Virginia School of Medicine, Charlottesville, Virginia
Impetigo is a highly contagious, superficial skin infection that most commonly affects children
two to five years of age. The two types of impetigo are nonbullous impetigo (i.e., impetigo con-
tagiosa) and bullous impetigo. The diagnosis usually is made clinically, but rarely a culture may
be useful. Although impetigo usually heals spontaneously within two weeks without scarring,
treatment helps relieve the discomfort, improve cosmetic appearance, and prevent the spread
of an organism that may cause other illnesses (e.g., glomerulonephritis). There is no standard
treatment for impetigo, and many options are available. The topical antibiotics mupirocin and
fusidic acid are effective and may be superior to oral antibiotics. Oral antibiotics should be
considered for patients with extensive disease. Oral penicillin V is seldom effective; otherwise
there is no clear preference among antistaphylococcal penicillins, amoxicillin/clavulanate,
cephalosporins, and macrolides, although resistance rates to erythromycin are rising. Topical
disinfectants are not useful in the treatment of impetigo. (Am Fam Physician 2007;75:859-64,
868. Copyright 2007 American Academy of Family Physicians.)

Patient information:
A handout on impetigo, written by the authors of this article, is provided on page 868.
Impetigo is a highly contagious infec- Epidemiology
tion of the superficial epidermis that Impetigo usually is transmitted through most often affects children two to five direct contact. In a study in the United years of age, although it can occur in Kingdom, the annual incidence of impetigo any age group. Among children, impetigo was 2.8 percent in children up to four years is the most common bacterial skin infec- of age and 1.6 percent among children five tion and the third most common skin dis- to 15 years of age.4 Nonbullous impetigo ease overall, behind dermatitis and viral accounts for approximately 70 percent of warts.1,2 Impetigo is more common in chil- cases. Patients can further spread the infec- dren receiving dialysis.1 The infection usu- tion to themselves or others after excoriat- ally heals without scarring, even without ing an infected area. Infections often spread treatment. Staphylococcus aureus is the most rapidly through schools and day care centers. important causative organism. Streptococcus Although children are infected most often pyogenes (i.e., group A beta-hemolytic strep- through contact with other infected children, tococcus) causes fewer cases, either alone or fomites also are important in the spread of in combination with S. aureus.3 impetigo. The incidence is greatest in the There are two types of impetigo: nonbul- summer months, and the infection often lous (i.e., impetigo contagiosa) and bullous. occurs in areas with poor hygiene and in
Nonbullous impetigo represents a host crowded living conditions.1,3
response to the infection, whereas a staphy-
lococcal toxin causes bullous impetigo and Diagnosis
no host response is required to manifest nonbullous impEtigo
clinical illness.3 The diagnosis usually is Nonbullous impetigo begins as a single red
made clinically and can be confirmed by macule or papule that quickly becomes a
Gram stain and culture, although this is vesicle. The vesicle ruptures easily to form
not usually necessary. Culture may be use-
an erosion, and the contents dry to form ful to identify patients with nephritogenic characteristic honey-colored crusts that may strains of S. pyogenes during outbreaks be pruritic (Figures 1 and 2). Impetigo often of poststreptococcal glomerulonephri- is spread to surrounding areas by autoin- tis or those in whom methicillin-resistant oculation. This infection tends to affect areas S. aureus is suspected.3 subject to environmental trauma, such as the Downloaded from the American Family Physician Web site at www.aafp.org/afp. Copyright 2007 American Academy of Family Physicians. For the private, noncommercial use of one individual user of the Web site. All other rights reserved. Contact [email protected] for copyright questions and/or permission requests.
Topical antibiotics such as mupirocin (Bactroban) and fusidic acid (not available in the United States) are the preferred first-line therapy for impetigo involving limited body surface area.
Oral antibiotics (e.g., antistaphylococcal penicil ins, amoxicil in/clavulanate [Augmentin], cephalosporins, macrolides) are effective for the treatment of impetigo; erythromycin is less effective.
Oral antibiotics should be considered for patients with impetigo who have more extensive disease and for disease associated with systemic symptoms.
Oral penicil in V, amoxicil in, topical bacitracin, and neomycin are not recommended for the treatment of impetigo.
Topical disinfectants such as hydrogen peroxide should not be used in the treatment of impetigo.
A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evi-dence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, see page 789 or http://www.aafp.org/afpsort.xml. extremities or the face. Spontaneous resolu- presentation is similar to that of primary tion without scarring typically occurs in sev- nonbullous impetigo.1 Table 1 provides a eral weeks if the infection is left untreated.5 selected differential diagnosis of nonbullous A subtype of nonbullous impetigo is com- mon (or impetiginous) impetigo, also called
secondary impetigo. This can complicate bullous impEtigo
systemic diseases, including diabetes mel-
Bullous impetigo most commonly affects litus and acquired immunodeficiency syn- neonates but also can occur in older children drome. Insect bites, varicella, herpes simplex and adults. It is caused by toxin-producing virus, and other conditions that involve S. aureus and is a localized form of staphylo-breaks in the skin predispose patients to coccal scalded skin syndrome.5,6 Superficial the formation of common impetigo. The vesicles progress to rapidly enlarging, flaccid Figure 1. Nonbullous impetigo on the face.
Figure 2. Nonbullous impetigo in the groin.
860  American Family Physician
www.aafp.org/afp Volume 75, Number 6March 15, 2007 Atopic dermatitis Chronic or relapsing pruritic lesions and abnormal y dry skin; flexural lichenification is common in adults; facial and extensor involvement is common in children Erythematous papules or red, moist plaques; usual y confined to mucous membranes or intertriginous areas Contact dermatitis Pruritic areas with weeping on sensitized skin that comes in contact with haptens (e.g., poison ivy) Lesions may be scaly and red with slightly raised "active border" or classic ringworm; or may be vesicular, especial y on feet Wel -defined plaques with adherent scale that penetrates into hair fol icles; peeled scales have "carpet tack" appearance Crusted lesions that cover an ulceration rather than an erosion; may persist for weeks and may heal with scarring as the infection extends to the dermis Herpes simplex virus Vesicles on an erythematous base that rupture to become erosions covered by crusts, usual y on the lips and skin Papules usual y seen at site of bite, which may be painful; may have associated urticaria Pemphigus foliaceus Serum and crusts with occasional vesicles, usual y starting on the face in a butterfly distribution or on the scalp, chest, and upper back as areas of erythema, scaling, crusting, or occasional bul ae Lesions consist of burrows and smal , discrete vesicles, often in finger webs; nocturnal pruritus is characteristic Abrupt onset of tender or painful plaques or nodules with occasional vesicles Thin-wal ed vesicles on an erythematous base that start on trunk and spread to face and extremities; vesicles break and crusts form; lesions of different stages are present at the same time in a given body area as new crops develop Information from reference 1. bullae with sharp margins and no surround- is present, and the condition may mimic ing erythema (Figures 3 and 4). When the bul- child abuse.7 Table 21 provides a selected dif- lae rupture, yellow crusts with oozing result. ferential diagnosis of bullous impetigo.
A pathognomonic finding is a "collar- ette" of scale surrounding the blister roof at prognosis and Complications
the periphery of ruptured lesions.5 Bullous No high-quality prognostic studies of
impetigo favors moist, intertriginous areas, impetigo are available. According to two
such as the diaper area, axillae, and neck recent nonsystematic reviews, impetigo usu-
folds. Systemic symptoms are not common ally resolves without sequelae within two
but may include weakness, fever, and diar-
weeks if left untreated.2,5 Only five placebo- rhea. Most cases are self-limited and resolve controlled randomized trials have been con-without scarring in several weeks. Bullous ducted. Seven-day cure rates in these trials impetigo appears to be less contagious than ranged from 0 to 42 percent.8 Adults seem to nonbullous impetigo, and cases usually are have a higher risk of complications.2,5 sporadic.3 Bullous impetigo can be mistaken Acute poststreptococcal glomerulonephri- for cigarette burns when localized, or for tis is a serious complication that affects scald injuries when more extensive infection between 1 and 5 percent of patients with March 15, 2007Volume 75, Number 6 www.aafp.org/afp American Family Physician  861
nonbullous impetigo.1,4 Treatment with treatment
antibiotics is not thought to have any effect The aims of treatment include relieving the
on the risk of poststreptococcal glomerulo-
discomfort and improving cosmetic appear- nephritis. Rheumatic fever does not appear ance of the lesions, preventing further spread to be a potential complication of impetigo. In of the infection within the patient and to oth-patients with chronic renal failure, especially ers, and preventing recurrence. Treatments those on dialysis and transplant recipients, ideally should be effective, inexpensive, and impetigo can complicate the condition. have limited side effects. Topical antibiotics Other rare potential complications include have the advantage of being applied only where sepsis, osteomyelitis, arthritis, endocardi- needed, which minimizes systemic side effects. tis, pneumonia, cellulitis, lymphangitis or However, some topical antibiotics may cause lymphadenitis, guttate psoriasis, toxic shock skin sensitization in susceptible persons. syndrome, and staphylococcal scalded skin A Cochrane review of interventions for impetigo identified only 12 good-quality studies of impetigo treatment.8 In a 2003 meta-analysis that included 16 studies, 12 received a good-quality score.4 Most of the studies addressed nonbullous impetigo, although the limited data for bullous and common impetigo suggest that similar con-clusions may be drawn regarding treatment.
Three studies found that topical antibiotics are clearly more effective than placebo for the treatment of impetigo.4,8 Most patients with localized disease should receive mupirocin (Bactroban) or fusidic acid (not available in the United States) because they are effec-tive and well tolerated. Data from four trials show that they are equally effective.4,8 Data on other topical antibiotics were limited, but bacitracin and bacitracin/neomycin were less effective. Adverse effects from topical anti-biotics were uncommon and, when present, Oral penicillin V was no more effective than placebo in a single study of patients with impetigo; however, the study was too small (and therefore lacked adequate statisti-cal power) to show a clinically meaningful difference between the treatment and pla-cebo groups, if one existed.8 Data comparing other oral antibiotics with placebo are not available. Numerous studies compared various oral antibiotics. Two systematic reviews showed that lactamase-resistant, narrow-spectrum penicillins; broad-spectrum penicillins; 862  American Family Physician
www.aafp.org/afp Volume 75, Number 6March 15, 2007 Bul ous erythema Vesicles or bul ae arise from a portion of red plaques, 1 to 5 cm in diameter, on the extensor surfaces of extremities Widespread vesiculobul ous eruption that may be pruritic; tends to favor the upper part of the trunk and proximal upper extremities Bul ous pemphigoid Vesicles and bul ae appear rapidly on widespread pruritic, urticarial plaques Herpes simplex virus Grouped vesicles on an erythematous base that rupture to become erosions covered by crusts, usual y on the lips and skin; may have prodromal symptoms Bul ae seen with pruritic papules grouped in areas in which bites occur Pemphigus vulgaris Nonpruritic bul ae, varying in size from 1 to several centimeters, appear gradual y and become generalized; erosions last for weeks before healing with hyperpigmentation, but no scarring occurs Vesiculobul ous disease of the skin, mouth, eyes, and genitalia; ulcerative stomatitis with hemorrhagic crusting is most characteristic feature History of burn with blistering in second-degree burns Stevens-Johnson–like mucous membrane disease fol owed by diffuse generalized detachment of the epidermis Thin-wal ed vesicles on an erythematous base that start on trunk and spread to face and extremities; vesicles break and crusts form; lesions of different stages are present at the same time in a given body area as new crops develop Information from reference 1. cephalosporins; and macrolides were, in extensive impetigo and those with systemic general, equally effective. Penicillin V and symptoms often are treated with oral anti-amoxicillin were less effective than cepha- biotics, there were no studies comparing losporins, cloxacillin, or amoxicillin/cla- oral and topical antibiotics in this subset vulanate (Augmentin).4,8 One study found of patients. Oral antibiotics can be used, cefuroxime (Ceftin) to be more effective however, based on expert opinion and tradi-than erythromycin, and erythromycin resis- tional practice.8 Adverse effects, particularly tance rates appear to be rising.4,8 nausea, are more common with oral anti-biotics, especially erythromycin, than with topical antibiotics.8 According to several systematic reviews,
mupirocin was as effective as several oral topiCAl DisinFECtAnts
antibiotics (dicloxacillin [Dynapen], cepha-
In a small, single study, topical disinfec- lexin [Keflex], ampicillin). Oral antibiot- tants, such as hexachlorophene (Phisohex), ics are recommended for patients who do were no better than placebo; and topical not tolerate a topical antibiotic, and should antibiotics were found to be superior to be considered for those with more exten- topical disinfectants in the treatment of sive or systemic disease. Basic prescribing impetigo.8 Comparison of oral penicillin information is summarized in Table 3. One V and hexachlorophene showed no dif-study comparing fusidic acid and cefurox- ferences in cure rates or improvement in ime found no difference in effectiveness, symptoms. Adverse effects from topical dis-and both mupirocin and fusidic acid were infectants were rare and, when present, were consistently more effective than oral eryth- mild; however, topical disinfectants are not romycin.4,7 Although patients with more recommended.8 March 15, 2007Volume 75, Number 6 www.aafp.org/afp American Family Physician  863
Dosing and duration of treatment Mupirocin 2% ointment Apply to lesions three times daily for three to Amoxicil in/clavulanate Adults: 250 to 500 mg twice daily for 10 days Children: 90 mg per kg per day, divided, twice daily for 10 days Cefuroxime (Ceftin) Adults: 250 to 500 mg twice daily for 10 days Children: 90 mg per kg per day, divided, twice daily for 10 days Cephalexin (Keflex) Adults: 250 to 500 mg four times daily for 10 days Children: 90 mg per kg per day, divided, two to four times daily for 10 days Dicloxacil in (Dynapen) Adults: 250 to 500 mg four times daily for 10 days Only available as Children: 90 mg per kg per day, divided, two to four times daily for 10 days Adults: 250 to 500 mg four times daily for 10 days Children: 90 mg per kg per day, divided, two to four times daily for 10 days *—Estimated cost to the pharmacist based on average wholesale prices (rounded to the nearest dol ar) in Red Book. Montvale, N.J.: Medical Economics Data, 2005. Cost to the patient wil be higher, depending on prescription fil ing fee.—Drug cost is for lowest dosage presented when possible. Address correspondence to John Gazewood, M.D., M.S.P.H., Department of Family Medicine, University of For this review we searched Ovid Evidence- Virginia Health System, P.O. Box 800729, Charlottesville, Based Medicine using the search term "impe- VA 22908 (e-mail: [email protected]). Reprints are not tigo." We also searched the National Guideline available from the authors.
Clearinghouse, the TRIP database, and Clini- Author disclosure: Nothing to disclose.
cal Evidence using the search term "impe- Figures provided by Kenneth Greer, M.D.
tigo." We searched Medline (1996 to 2005) using the Clinical Evidence search strategy.
1. Brown J, Shriner DL, Schwartz RA, Janniger CK. Impe- tigo: an update. Int J Dermatol 2003;42:251-5.
CHARLES COLE, M.D., is an associate professor of clini- 2. Sladden MJ, Johnston GA. Common skin infections in cal family medicine at the University of Virginia School children. BMJ 2004;329:95-9.
of Medicine, Charlottesvil e, and medical director of the Stoney Creek Family Practice, Nel ysford, Va. Dr. 3. Hirschmann JV. Impetigo: etiology and therapy. Curr Clin Top Infect Dis 2002;22:42-51.
Cole earned his medical degree from the University of Maryland School of Medicine, Baltimore, and completed a 4. George A, Rubin G. A systematic review and meta- residency in family medicine at the University of Virginia, analysis of treatments for impetigo. Br J Gen Pract Charlottesvil e, where he also served as chief resident. 5. Mancini AJ. Bacterial skin infections in children: JOHN GAZEWOOD, M.D., M.S.P.H., is an associate the common and the not so common. Pediatr Ann professor of family medicine and residency program director at the University of Virginia School of Medicine, 6. Johnston GA. Treatment of bul ous impetigo and the Charlottesville. He earned his medical degree from staphylococcal scalded skin syndrome in infants. Expert Vanderbilt University, Nashvil e, Tenn., and completed a Rev Anti Infect Ther 2004;2:439-46.
family medicine residency at the University of Missouri– 7. Koning S, Verhagen AP, van Suijlekom-Smit LW, Morris A, Columbia School of Medicine. After five years in private Butler CC, Van der Wouden JC. Interventions for impe- practice, Dr. Gazewood earned a master of science in tigo. Cochrane Database Syst Rev 2003;(2):CD003261.
public health degree and completed faculty development 8. Mudd SS, Findlay JS. The cutaneous manifestations and and geriatric fel owships at the University of Missouri– common mimickers of physical child abuse. J Pediatr Columbia School of Medicine.
Health Care 2004;18:123-9.
864  American Family Physician
www.aafp.org/afp Volume 75, Number 6March 15, 2007

Source: http://www.ringsidemedicine.com/impetigoreview.pdf

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