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Impetigo, Emergency Medicine

Basics

Description

- Most prevalent in children aged 2-5 yr - More common in summer months and warm and humid climates - Predisposing factors: - Minor trauma, esp. around nose area - Burns - Insect bites - HIV infection - Diabetes mellitus - Existing skin disease - Varicella infection

- Classic impetigo: - The result of bacteria entering through traumatic skin portal from scratch, abrasion, or insect bite - Caused by Staphylococcus aureus, group A β-hemolytic streptococci, or both - Often associated with poor hygiene - Treatment of both streptococci and S. aureus

- Classic (nonbullous) impetigo: - Begins as a single 2-4 mm erythematous macule or papule that may evolve into a vesicle or pustule, on a red base - Rupture of the vesicle, usually within 24 hr, leaves a honey-colored, dark brown, or reddish-black exudative crust - Highly contagious - Often pruritic, may be spread from the original site of infection by scratching - Mild lymphadenopathy may be seen, usually not lymphadenitis - Systemic manifestations are rare - Rheumatic fever does not occur following streptococcal skin infection - Skin infections with nephritogenic strains of group A streptococci are major antecedents of poststreptococcal glomerulonephritis

- Bullous impetigo: - Occurs most commonly in the neonate, but can occur at any age - Lesions begin as vesicles that turn into flaccid bullae with clear yellow fluid - Nikolsky sign is absent - Large, fragile bullae rupture quickly, leaving only a shiny, erythematous base with peeling edges

- Biopsy is generally not needed for diagnosis - If biopsy is performed: - Subcorneal epidermal cleavage plane - Inflammatory infiltrate of neutrophils and lymphocytes in the upper dermis - Subcorneal blisters with occasional acantholytic cells

- Apply dressings to cover for transport - Gloves must be worn, as agents can be transmitted person to person - Cautions: - Maintain universal precautions - Siblings of affected children in same household should be checked for lesions

  • Impetigo is a common infection of the skin
  • Primary infection:Infection of minor breaks in the skin
  • Secondary infection:Infection of previously existing skin lesions, known as "impetiginization"пїЅ
  • Most prevalent in children aged 2-5 yr
  • More common in summer months and warm and humid climates
  • Predisposing factors:Minor trauma, esp. around nose areaBurnsInsect bitesHIV infectionDiabetes mellitusExisting skin diseaseVaricella infection
  • Complications:Acute poststreptococcal glomerulonephritis1-5% in patients with nonbullous impetigoSepsisCellulitisEndocarditisToxic shock syndromeStaphylococcal scalded skin syndrome (SSSS)

Etiology

  • Classic impetigo:The result of bacteria entering through traumatic skin portal from scratch, abrasion, or insect biteCaused by Staphylococcus aureus, group A β-hemolytic streptococci, or bothOften associated with poor hygieneTreatment of both streptococci and S. aureus
  • Bullous impetigo:Caused by S. aureus, phage group IIEpidermal cleavage is caused by staphylococcal exfoliative toxins A, B, and D, which are serine proteases that bind and cleave desmoglein 1, an intercellular adhesion molecule in desmosomes

Zinc supplementation to mother during pregnancy may lead to decreased incidence in infants пїЅ

Diagnosis

Signs and Symptoms

  • Classic (nonbullous) impetigo:Begins as a single 2-4 mm erythematous macule or papule that may evolve into a vesicle or pustule, on a red baseRupture of the vesicle, usually within 24 hr, leaves a honey-colored, dark brown, or reddish-black exudative crustHighly contagiousOften pruritic, may be spread from the original site of infection by scratchingMild lymphadenopathy may be seen, usually not lymphadenitisSystemic manifestations are rareRheumatic fever does not occur following streptococcal skin infectionSkin infections with nephritogenic strains of group A streptococci are major antecedents of poststreptococcal glomerulonephritis
  • Bullous impetigo:Occurs most commonly in the neonate, but can occur at any ageLesions begin as vesicles that turn into flaccid bullae with clear yellow fluidNikolsky sign is absentLarge, fragile bullae rupture quickly, leaving only a shiny, erythematous base with peeling edges

History

Fever and constitutional symptoms are uncommon пїЅ

Physical Exam

  • Common sites of infection:
  • The diagnosis is made based on observation of the classic exam findings, especially appearance, and distribution

Essential Workup

Cultures of fluid from bullae or pustules may be considered in those cases refractory to traditional therapy or if methicillin-resistant S. aureus (MRSA) is of particular concern during an outbreak пїЅ

Diagnosis Tests & Interpretation

Lab

  • Antistreptolysin O titer after streptococcal impetigo is scant
  • AntiDNase B response readily occurs; 90% of patients with nephritis complicating streptococcal skin infections have elevated titers
  • Urinalysis to evaluate for hematuria or proteinuria which might suggest onset of poststreptococcal glomerulonephritis

Imaging

Not usually indicated пїЅ

Diagnostic Procedures/Surgery

  • Biopsy is generally not needed for diagnosis
  • If biopsy is performed:Subcorneal epidermal cleavage planeInflammatory infiltrate of neutrophils and lymphocytes in the upper dermisSubcorneal blisters with occasional acantholytic cells
  • Gram stain of blister fluid may show PMNs and gram-positive cocci in chains or clusters

Differential Diagnosis

  • Herpes simplex
  • Varicella zoster (shingles)
  • Atopic dermatitis
  • Contact dermatitis
  • Dermatophytosis
  • Erysipelas
  • Candidiasis
  • Scabies
  • Folliculitis
  • Pediculosis
  • Pemphigus vulgaris
  • Bullous pemphigoid
  • Seborrheic dermatitis
  • Thermal burns
  • Stevens-Johnson syndrome
  • Bullous erythema multiforme
  • SSSS, caused by systemic spread of exfoliatin in susceptible individuals
  • Pemphigus neonatorum (Ritter disease), or SSSS in the newborn
  • Toxic epidermal necrolysis
  • Cutaneous anthrax

Treatment

Pre-Hospital

  • Apply dressings to cover for transport
  • Gloves must be worn, as agents can be transmitted person to person
  • Cautions:Maintain universal precautionsSiblings of affected children in same household should be checked for lesions

Initial Stabilization/Therapy

In healthy children or adults, classic or bullous impetigo is not a life-threatening condition and does not require resuscitative measures пїЅ

Ed Treatment/Procedures

  • Small nonbullous lesions may be treated with topical therapy alone
  • Larger, widespread lesions, or presence of bullous impetigo, or presence of lymphadenopathy should be treated with systemic therapy
  • Systemic treatment should include a β-lactamase-resistant penicillin, cephalosporin, or macrolide antimicrobial for 10 days:If no response, check for MRSA and switch antibiotic to cover for MRSA
  • Systemic antibiotic advisable during epidemics of acute poststreptococcal glomerulonephritis or in communities with widespread MRSA
  • Local care should include cleansing, removal of crusts, and application of wet dressings to the affected areas

Medication

  • All treatment regimens are 10 days, except for topical retapamulin, which is used for 5 days and may enhance compliance, and oral azithromycin, which lasts 9 days when taken for 5 days
  • Avoid use of erythromycin if high incidence of erythromycin resistance of streptococci or staphylococci in the community
  • Oral:Amoxicillin/clavulanic acid: 250 mg PO q8h (peds: 30 mg/kg/d PO in div. doses q8h)Azithromycin: 500 mg PO on day 1; 250 mg PO days 2-5 (peds: 10 mg/kg PO on day 1; 5 mg/kg PO days 2-5)Cephalexin: 500 mg PO QID (peds: 25-50 mg/kg/d PO in div. doses q8-12h)Clarithromycin: 250 mg PO q12h (peds: 15 mg/kg in div. doses q12h)Clindamycin: 150 mg PO TID (peds: 5 mg/kg TID)Dicloxacillin: 250 mg PO q6h (peds: 25-50 mg/kg/d PO in div. doses q6h)Doxycycline: 100 mg PO q12h when MRSA suspected: (Peds over 8 yr and under 45 kg, give 4.5 mg/kg/d in div. doses q12h). Not recommended for children under 8 yrErythromycin ethylsuccinate: 250 mg PO q6h (peds: 40 mg/kg/d PO in div. doses q6h)Trimethoprim-sulfamethoxazole DS: 1 tab PO BID for 10 days (peds: >2 mo; 4 mg/kg of trimethoprim component PO q12h for 10 days); Useful when MRSA suspectedLinezolid: 600 mg PO BID-expensive, used only for multiallergic patients or MRSA (peds: Not approved for children)
  • Topical:Mupirocin (2% ointment [Bactroban]): Adult and peds: Apply topically to affected area TID (nonbullous impetigo only) for 10 days.Retapamulin (1% ointment) (Altabax): Adult and peds >9 mo: Apply topically to affected areas BID for 5 days.

First Line

Topical: пїЅ

  • Mupirocin: (up to 46% of US 300 strain of Community-acquired MRSA carry gene encoding for resistance to mupirocin)

Second Line

  • Topical:Retapamulin (package insert says not for MRSA due to not enough cases studied, but has shown effect on mupirocin-resistant MRSA)
  • Oral antibiotics:Amoxicillin/clavulanic acidCephalosporinsDicloxacillinErythromycinDoxycycline

Follow-Up

Disposition

Admission Criteria

  • Admission for impetigo alone is rarely necessary
  • Patients with disease that is widespread, especially widespread bullae, or with larger areas of denuded skin, and dehydration, or refractory to outpatient therapy
  • Toxic, ill-appearing, or immunocompromised patients require admission, as do neonates suspected of having sepsis
  • Nephritis may already be present at time patients present for care if presentation is delayed >4-5 days
  • More typically, nephritis, if seen, occurs 2-4 wk after a streptococcal skin infection

Discharge Criteria

  • Patients should not be toxic appearing
  • Patients/caregivers should be able to comply with the recommended treatment regimen
  • Follow-up for re-evaluation

Issues for Referral

Periorbital edema, leg swelling, or hematuria or proteinuria should suggest poststreptococcal glomerulonephritis and referral to nephrologist пїЅ

Follow-Up Recommendations

  • Follow-up with primary care physician should be arranged to assure resolution without complications
  • Return for failure of lesions to respond
  • Return for development of hematuria, periorbital edema, or leg swelling

Pearls and Pitfalls

  • Treat with systemic antibiotics in the presence of bullous impetigo or if lymphadenopathy is present
  • Increasing antibiotic resistance continues to limit ability to use historic standard antibiotic protocols
  • Mupirocin resistance exists, should be suspected in failures to respond and switch to retapamulin
  • Cultures and sensitivity must be checked for recalcitrant lesions
  • Relapse, representing reinfection, may occur if other affected family members are not treated at the same time

Additional Reading

  • Darmstadt пїЅGL, Osendarp пїЅSJ, Ahmed пїЅS, et al. Effect of antenatal zinc supplementation on impetigo in infants in Bangladesh. Pediatr Infect Dis J. 2012;31:407-409.
  • Koning пїЅS, van der Wouden пїЅJC, Chosidow пїЅO, et al. Efficacy and safety of retapamulin ointment as treatment of impetigo: Randomized double-blind multicentre placebo-controlled trial. Br J Dermatol. 2008;158:1077-1082.
  • Wolfson пїЅAB, Hendey пїЅGW, Ling пїЅLJ, et al., eds. Harwood Nuss' Clinical Practice of Emergency Medicine. 5th ed. Philadelphia, PA: Lippincott; 2010.

See Also (Topic, Algorithm, Electronic Media Element)

  • Cellulitis
  • Erysipelas
  • Toxic Epidermal Necrolysis

Codes

ICD9

  • 684 Impetigo
  • 694.3 Impetigo herpetiformis
  • 704.8 Other specified diseases of hair and hair follicles

ICD10

  • L01.00 Impetigo, unspecified
  • L01.01 Non-bullous impetigo
  • L01.03 Bullous impetigo
  • L01.09 Other impetigo
  • L01 Impetigo
  • L40.1 Generalized pustular psoriasis

SNOMED

  • 48277006 Impetigo (disorder)
  • 399183005 Impetigo bullosa (disorder)
  • 238374001 Non-bullous impetigo
  • 200706004 Impetigo neonatorum (disorder)