Impetigo
Impetigo: Excerpt from The 5-Minute Pediatric Consult
Y. Lily Higgins, MS, MDStephen Higgins, MD
Impetigo - BASICS
Impetigo - description
- Impetigo is a bacterial skin infection of the superficial layers of the epidermis, characterized by honey-colored, crusted patches or bullae with a central crust
- Impetigo has 2 clinical varieties: Nonbullous impetigo (impetigo contagiosa), the most prevalent form; and bullous impetigo.
Impetigo - general prevention
- Wash hands carefully.
- Avoid sharing soiled towels, clothes, or bed sheets, and grooming items such as nail scissors, tweezers, razors, and toothbrushes.
- Use antibacterial soap to lower the incidence of impetigo.
Impetigo - epidemiology
- The most common bacterial skin infection in children
- Transmitted by direct contact
- Highly contagious and rapidly disseminated through day care centers and school
- Fomites can be a source of infection.
- Associated with crowded living
Impetigo - incidence
Incidence is greatest during the summer, which may be explained by a higher incidence of skin trauma and increased skin contact between children during the summer months.
Impetigo - pathophysiology
- Bacteria invade areas of the skin that are not intact.
- In early lesions, histology shows vesicopustular formation in the subcorneal region of the epidermis, and neutrophils can be found. The blister cavity is larger in bullous impetigo than in nonbullous impetigo.
- A serous crust and neutrophilic debris overlying a superficially eroded epidermis may be seen in later stages on histopathologic evaluation.
Impetigo - etiology
Nonbullous impetigo: Group A-hemolytic streptococci, Staphylococcus aureus, or both are the causative agents. Previously, group A streptococcus was the most common bacterium associated with nonbullous impetigo, but now S. aureus is the most common.
- Bullous impetigo: S. aureus is almost always the causative agent. The formation of bullae is mediated by production of exfoliative toxins. The exfoliative toxins excreted by associated strains of S. aureus produce a cleavage plane under the stratum corneum allowing the bacteria to proliferate and spread.
Impetigo - DIAGNOSIS
Impetigo - signs & symptoms
Impetigo - history
- Ask about exposure history, because lesions are highly contagious.
- Obtain history of other skin conditions that could cause secondary impetigo
Impetigo - physical exam
- Nonbullous impetigo starts as a small, tender, erythematous papule. Often, there is evidence of minor skin disruption by lesions such as an insect bite, eczema, or a mild abrasion. The papule then becomes “honey-crusted,” with a serous discharge.
- Bullous impetigo appears on exposed and moist skin. It starts as a transparent bulla that ruptures easily, exposing a moist erosion surrounded by a thin rim of scale.
- Impetigo may itch; but generally there is little or no pain, and minimal surrounding erythema.
- Local lymphadenopathy is seen in 90% of cases.
- Constitutional symptoms, such as fever, are rare and may suggest systemic bacterial infection.
- It is clinically impossible to distinguish staphylococcal from streptococcal impetigo, though most cases of bullous impetigo are due to staphylococci.
Impetigo - tests
Impetigo - lab
- Culture of the lesion, though not necessary in the majority of cases, can be obtained by swabbing the blister fluid or the skin beneath the lifted edge of a crusted plaque; obtain culture prior to therapy or in cases of treatment failure.
- Biopsy of the lesion: When the cause of the lesion(s) is in doubt, a biopsy should be considered using histopathologic evaluation, and possibly immunofluorescence staining.
- Immunologic tests can be used to confirm recent infection with group A streptococcus.
- CBC shows leukocytosis in ~50% of patients.
Impetigo - differencial diagnosis
- Nonbullous impetigo:
- Atopic dermatitis
- Candidiasis
- Scabies
- Pediculosis
- Childhood discoid lupus erythematosus
- Tinea corporis
- Varicella
- Herpes simplex virus infection
- Ecthyma
- Bullous impetigo:
- Thermal burn
- Bullous pemphigoid
- Pemphigus vulgaris
- Stevens-Johnson syndrome
- Bullous erythema multiforme
- Necrotizing fasciitis
Impetigo - TREATMENT
Impetigo - general measures
- Local wound care, removal of crusts, and the application of wet dressings may be helpful. There is little evidence to show that disinfecting solutions, such as providone-iodine and chlorhexidine, are of any benefit.
- Topical antibiotic treatment with mupirocin for 7–10 days has been shown to be as effective as treatment with oral antibiotics, and topical treatment is associated with less side effects. A rising resistance rate of S. aureus to funisidic acid has been developing rapidly in Europe, suggesting the need for prudent use of these antibiotics. Funisidic acid currently is not available in the US.
- For treatment of localized impetigo, mupriocin has been shown to be more effective than other topical antibiotics such as neomycin, bacitracin, polymicin B and gentamicin.
- If impetigo is widespread or the lesions are in an area not conducive to topical therapy, consider systemic oral antimicrobial therapy with erythromycin and cloxacillin.
- In areas with a high S. aureus resistance to erythromycin, consider using lactamase-resistant antimicrobials, such as cephalexin, cefadroxil, dicloxicillin, or amoxicillin combined with potassium clavulanate should be used.
- There is no evidence that a 10-day course of oral antibiotics is superior to 7 days. Beware of emerging resistance patterns when prescribing antibiotics.
- There is an increasing incidence of community acquired MRSA. If the staphylococcus is methicillin-resistant, oral trimethoprim/sulfamethoxazide or clindamycin should be considered.
- Trimethoprim-sulfamethoxazide (TMP-SMX) has activity against most MRSA isolates; however, it is ineffective against group A streptococcus. TMP-SMX is generally not recommended for empiric therapy for impetigo and should only be used if the drainage has been cultured and the isolate is susceptible.
- Bullous impetigo in neonates must be treated by parenteral antibiotics. First-line agents should be lactamase-resistant antistaphylococcal penicillins, such as methicillin, oxacillin, or nafcillin.
Impetigo - FOLLOW UP
Impetigo - prognosis
- Without treatment, individual localized lesions usually resolve spontaneously within 2 weeks; however, topical antibiotics have shown a better cure rate than placebo.
- Most lesions resolve without scarring.
- Spreading of the infection by fingers or clothing to other areas of the skin is common.
- Rarely, a chronic ulcer may form.
Impetigo - complications
- Nonhematogenous spread may result in:
- Cellulitis
- Lymphangitis
- Scarlet fever
- Acute post-Streptococcal glumerulonephritis
- Exacerbation of guttate psoriasis
- Hematogenous spread may result in:
- Osteomyelitis
- Septic arthritis
- Pneumonia
- Septicemia
Impetigo - patient monitoring
- If a 7-day course of oral therapy does not eliminate the lesion(s), a culture of the serous fluid from a crusted lesion should be obtained. Antimicrobial susceptibility of the isolate(s) should be performed.
- Consider testing patients with recurrent impetigo for nasopharyngeal carriage of MRSA. Intranasal application of mupirocin can temporarily eliminate nasal carriage of methicillin-susceptible and resistant strains of S. aureus in >90% of individuals within 2–4 days.
Impetigo - bibliography
Brown J, Shriner DL, Schwartz RA, et al. Impetigo: An update. Int J Dermatol. 2003;42:251–255.Darmstadt GL. A guide to superficial strep and staph skin infections. Contemp Pediatr. 1997;14:95–116.Hanakawa Y, Schecter N, Normal M, et al. Molecular mechanisms of blister formation in bullous impetigo and staphylococcal scalder skin syndrome. J Clin Invest. 2002;110:53–60.Jain A, Daum RS. Staphylococcal infections in children: Part 1. Pediatr Rev. 1999;20:183–191.Koning S, van Suijlekom-Smit LW, Nouwen Tl, et al. Fusidic acid cream in the treatment of impetigo in general practice: Double blind randomized placebo controlled trial. Brit Med J. 2002;324:1–5.Koning S, Verhagen A, van Suiglekom-Smith L. Interventions for impetigo. Cochrane Database Syst Rev. 2004;(2):CD003261.Luby S, Agboatwalla M. The effect of antibacterial soap on impetigo incidence. Am J Trop Med Hyg. 2002;67(4):430–435.Rubin, GA. A systemic review and meta-analysis of treatments of impetigo. Brit J Gen Pract. 2003;53:480–487.
Impetigo - CODES
Impetigo - icd9
684 Impetigo
Impetigo - FAQ
- Q: Should systemic therapy be started to prevent the development of acute post-streptococcal glomerulonephritis following streptococcal impetigo?
- A: There are no data available to show that antimicrobial therapy reduces the incidence of glomerulonephritis. It is postulated that by the time impetigo is diagnosed, there is already extensive antigenic exposure.
- Q: My patient is allergic to penicillin. Which antibiotic should be used for impetigo for this patient?
- A: Erythromycin is often effective, but should be avoided in areas where there is known resistance. The 2 macrolides, azithromycin and clarithromycin, are effective but costly.
- Q: When can a child return to school or day care?
- A: Children should not return to school until they have received antibiotic treatment for at least 24 hours. Lesions should be kept covered when returning to school.
Book Source Details
- Book Title: The 5-Minute Pediatric Consult
- Author(s): M. William Schwartz MD; et al.
- Year of Publication: 2008
- Copyright Details: The 5-Minute Pediatric Consult, Copyright © 2008 Lippincott Williams & Wilkins.
More About Impetigo
More Medical Textbooks Online about Impetigo
Review other book chapters online related to Impetigo:
Medical Books Excerpts
- Impetigo
- "Professional Guide to Diseases (Eighth Edition)" (2005)
- [ read ]
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: The 5-Minute Pediatric Consult
Authors: M. William Schwartz MD; et al.
Publisher: Lippincott Williams & Wilkins
Copyright: 2008
ISBN: 0-7817-7577-9
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