Dermatology | Infectious Diseases
Impetigo
Background
- Definition
- Infection of the superficial layers of the epidermis that is highly contagious and most common due to group A Streptococcus (GAS), Staphylococcus aureus, or both
- Synopsis
- Recently, MRSA is an important etiology to rule out
- Most commonly presents as erythematous plaques w/ a yellow crust
- Highly contagious, spreads easily
- Diagnosis
- Symptoms and clinical manifestations
- Treatment
- Topical and oral antibiotics
- Symptom control
Pathophysiology
- Etiology/Risk Factors
- Most common in children 2-5 yo
- Triggers breaking down skin and increasing susceptibility
- Burns
- Herpes
- Insect bites
- Lice
- Scabies
- Scratching
- Trauma
- Varicella
- Malnutrition
- Immunosuppression
- Daycare attendance
- Overcrowding
- Diabetes
- Poor hygiene
- Pathology
- Superficial skin infection
- Usual colonization in nares/pharynx
- Non-bullous: most common
- Start as papules that evolve to vesicles with erythematous bases
- Then to pustules that rupture to form golden “honey-colored” crust
- Bullous: usually younger children
- Vesicles enlarge to form flaccid bullae
- Later rupture and leave a brown-colored crust
- Strains of S. aureus with exfoliative toxins
- Loss of cell adhesion in superficial epidermis
- Ecthyma: ulcerative impetigo extending into deep dermis
- “Punched-out” ulcers with yellow crust and violaceous edges
- Contagious, transferred through fomites (clothes, toys)
- Handwashing
- Essential to prevent spread
- May be acquired at birth if PROM
- Epidemiology
- Incidence/Prevalence
- 10% of all skin disorders affecting children
- Most common in
- Warm, humid areas
- Southeast US
- Peak incidence
- Higher incidence
- Areas with high crowding, poor hygiene
- Morbidity/Mortality
- Can progress to any Staph/Strep disease
- Cellulitis
- Cutaneous abscess (esp. MRSA) lymphadenitis
- Staph scalded skin syndrome
- Meningitis
- Sepsis
- Post-streptococcal glomerulonephritis
- Antibiotic tx does not reduce risk
- Neonates
- More susceptible to developing meningitis/sepsis
Diagnostics
- History/Symptoms
- Hx of skin trauma
- Rash on exposed
- Skin of face (mouth/nose)
- Extremities
- Begins painless, occasionally pruritic
- Yellow/honey-colored lesions (crusted)
- Bullous lesions that spontaneously rupture may be present
- May have associated F/D, weakness
- Hx of acute glomerulonephritis (Strep)
- Physical Exam/Signs
- Nonbullous impetigo
- 1-3 mm macule evolves into
- Serous discharge
crusted plaques with erythematous base
- Weeping, erythematous, shallow erosions or ulcerations
- Heals without scarring
- +/- regional LAD
- Bullous impetigo
- Fragile, fluid-filled vesicle or bulla < 3 cm (View image)
- Most commonly
- Face
- Buttocks
- Trunk
- Perineum
- Extremities
- Ruptures in 1-2 days
- Resulting in superficial erosion with moist, erythematous base
- May have scalded skin appearance
- Usually LAD
- Ecthyma
- Transient vesicular lesions
- With thick, adherent crust
- Central area
- Erythematous, indurated periphery
- Central ulcer
scarring
- Edema, HTN
- Labs/Tests
- Clinical diagnosis
- Urinalysis
- Rule-out glomerulonephritis
- Culture & Stain for unknown Dx
- Nare cultures
- Potential carriers, close contacts
- C&S
- Treatment failures for Abx adjustment
- Bacterial cultures
- ASO
- Not indicated
- Response is weak from impetigo alone
- Imaging
- Usually not routine
- Unless indicated by underlying pathology
- Deep wound
- Organ failure signs
- Differential Diagnosis
Treatment
- Initial/Prep/Goals
- Contact isolation
- Local wound care
- Wet dressings
- Cleansing of lesions
- Insufficient evidence
- To compare effectiveness of topical vs oral Abx
- Medical/Pharmaceutical
- Topical antibiotics
- Systemic antibiotics
- MRSA
- Complications
- Post-streptococcal glomerulonephritis
- May occur 2-3 weeks after skin infection
- Rheumatic fever
- Meningitis
- Renal failure
- Septic arthritis
- Scarlet fever
- Sepsis
- Staphylococcal scaled skin syndrome
- Prevention
- Wash body and hair often with soap and clean, running water
- Wash the clothes, linens, and towels of anyone with impetigo every day
- Don't share clothes, linens, or towels with anyone who has impetigo
Disposition
- Admission Criteria
- Admit if severe secondary complications
- Consult(s)
- Neonatology for neonate infections
- Discharge/Follow-Up instructions
- Isolation from school until > 24 hours after Abx treatment
- Patient no longer infectious
- Follow up with PCP as appropriate
- Follow-up within 7-10 days; lesions should be healed
- If still present: C&S lesions, add PO Abx
- Examine, treat family members, close contacts
- Mupirocin cream to nares in carriers (monthly if chronic)
- Monitor for glomerulonephritis:
- May occur up to 5 weeks after disease
References
- Habif TP. Bacterial infections. Clinical Dermatology. 5th ed. St. Louis, Mo: Mosby-Elsevier, 2009;Chapter 9
- Mandell GL, Bennett JE, Dolin R, Pasternack MS, Swartz MN, et al. Cellulitis, necrotizing fasciitis, and subcutaneous tissue infections. Principles and Practice of Infectious Diseases, 7th ed. Philadelphia, Pa: Elsevier-Churchill Livingstone, 2009;Chapter 90
- Moulin F, Quinet B, Raymond J, Gillet Y, Cohen R. [Managing children skin and soft tissue infections]. Arch Pediatr. Oct 2008;15(Suppl 2):S62-67
- Bernard P. Management of common bacterial infections of the skin. Curr Opin Infect Dis. Apr 2008;21(2):pp.122-128
- Cole C, Gazewood J. Diagnosis and treatment of impetigo. Am Fam Physician, Mar 15, 2007;75(6):pp.859-864
- Mertz PM, Marshall DA, Eaglstein WH, Piovanetti Y, Montalvo J. Topical mupirocin treatment of impetigo is equal to oral erythromycin therapy. Arch Dermatol. Aug 1989;125(8):pp.1069-1073
- Koning S, van der Sande R, Verhagen AP, et al. Interventions for impetigo. Cochrane Database Syst Rev. Jan 18, 2012.
- Cydulka RK, Stewart MH Dermatologic Presentations: Impetigo. In Marx JA, Hockberger RS, Walls RM eds. Rosen’s Emergency Medicine Concepts and Clinical Practice. 5th ed. St. Louis, MO: Mosby; 2002: 1640
- Malley R. Skin and Soft Tissue Infections: Impetigo. In Tintinalli JE, Kelen GD, Stapczynski JS eds. Emergency Medicine: A Comprehensive Study Guide. 6th ed. New York, NY: McGraw-Hill; 2004:779-780
- McMillan JA, Feigin RD, DeAngelis C, Jones MD. Oski's Pediatrics: Principles & Practice, 4th ed, Philadelphia, PA:Lippincott Williams & Wilkins, 2006;Chapter 74
- Cole C, Gazewood J. Diagnosis and treatment of impetigo. Am Fam Physician. 2007 Mar 15. 75(6):859-64.
- Impetigo. StatPearls [Internet]. Available at: https://www.ncbi.nlm.nih.gov/books/NBK430974/. [Accessed September 2024]
- Centers for Disease Control and Prevention (CDC). About Impetigo. Available at: https://www.cdc.gov/group-a-strep/about/impetigo.html. [Accessed September 2024]
- Centers for Disease Control and Prevention (CDC). Preventing Group A Strep Infection. Available at: https://www.cdc.gov/group-a-strep/prevention/index.html. [Accessed September 2024]
Contributor(s)
- Hilbert, Sue-Lin, MD
- Ballarin, Daniel, MD
- Singh, Ajaydeep, MD
Updated/Reviewed: September 2024