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For further information, see CMDT Part 33-01: Streptococcal Infections

Key Features

Essentials of Diagnosis

  • A rapidly spreading infection involving the fascia of deep muscle

  • Areas that are often affected

    • An extremity

    • Head and neck

    • Perinanal area or genital area ("Fournier gangrene")

  • Skin or blunt trauma injury may precede the infection

  • Patients who are more susceptible are

    • Immunosuppressed

    • Diabetic

    • At extremes of age (elderly or neonates)

    • Affected by liver disease

General Considerations

  • Distinguishing necrotizing fasciitis from necrotizing myositis may be difficult as skeletal muscle and fascia are involved in both syndromes

  • Necrotizing fasciitis

    • Most often monomicrobial

    • Usual causative agent is Streptococcus pyogenes (Group A beta-hemolytic streptococci)

    • Can also be caused by other streptococcal species, and occasionally by Staphylococcus aureus

    • Infections can be polymicrobial (mixed aerobic and anaerobic bacteria)

    • A history of exposure to brackish water or marine life should raise suspicion for Vibrio vulnificans or Aeromonas species

    • Patients with burn injuries are susceptible to Pseudomonas species

  • Necrotizing myositis

    • Often caused by Clostridia species (clostridial myonecrosis or "gas gangrene")

Clinical Findings

  • Presentation is similar to severe cellulitis

  • Rapid progression

  • Systemic toxicity

  • Severe pain

  • Pain often subsides as nerves are destroyed

  • Multiorgan failure is common as infection progresses

Diagnosis

Laboratory Findings

  • Elevated white blood cell count, erythrocyte sedimentation rate and C-reactive protein

  • Elevated creatine kinase may indicate muscle involvement

  • Blood, wound, and tissue cultures should be obtained

  • Histologic specimens may demonstrate

    • Extensive tissue destruction

    • Thrombosis of blood vessels

    • Bacteria spreading along fascial planes

Imaging

  • CT or MRI of the affected area may show gas in tissues or fascial plane infection

  • Imaging may also appear normal, so rely on clinical suspicion and surgical evaluation

Treatment

Medication

  • Antibiotic therapy should then be tailored to culture results

  • Broad-spectrum antibiotic therapy

    • Should be initiated whenever the diagnosis is suspected

    • Should cover aerobic and anaerobic organisms

    • Initial therapy typically consists of

      • Carbapenem (meropenem or imipenem) or piperacillin-tazobactam plus an agent with activity against methicillin-resistant S aureus (vancomycin, linezolid or daptomycin) plus clindamycin for its antitoxin and other effects against toxin-producing strains of streptococci and staphylococci

  • Patients with exposure histories that suggest less common etiologies should have additional therapy targeted to those organisms

  • Intravenous immunoglobulin for streptococcal necrotizing soft tissue infections

    • Dose: 1 g/kg on day 1, followed by 0.5 g/kg on days 2 and 3

    • Has been shown to reduce mortality when added to surgical and antibiotic therapy

Surgery

  • Early and extensive debridement is essential for survival

  • Surgical evaluation should not be delayed while awaiting imaging or other diagnostic tests, especially in the setting of rapid progression of clinical manifestations

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