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For further information, see CMDT Part 35-01: 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

    • Perianal area or genital area (called "Fournier gangrene" in this region)

  • Skin or blunt trauma injury may precede the infection

  • Patients who are more susceptible are

    • Immunosuppressed

    • Diabetic

    • At extremes of age (older adults or neonates)

    • Affected by liver disease

General Considerations

  • Necrotizing fasciitis

    • Most often monomicrobial due to Streptococcus pyogenes (Group A beta-hemolytic streptococci)

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

    • Infections can also 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

    • May present similarly and also involves both fascia and skeletal muscle

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

CLINICAL FINDINGS

  • Presentation is similar to severe cellulitis

  • Systemic toxicity

  • Severe pain

  • May be anesthesia of the involved area due to destruction of nerves as infection advances through the fascial planes

  • Infection can progress rapidly

  • Debridement is often indicated

  • Multiorgan failure is common

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

Medications

  • Broad-spectrum antibiotic therapy

    • Should be initiated whenever the diagnosis is suspected

    • Should cover aerobic and anaerobic organisms

  • Initial therapy for patients with normal kidney function typically consists of

    • Intravenous carbapenem (meropenem, 2 g every 8 hours, or imipenem, 1 g every 6 hours) or piperacillin-tazobactam, 3.375 g every 6 hours (unless Pseudomonas is suspected, in which case the dose should be increased to 4.5 g every 6 hours), 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

  • Clindamycin can inhibit the production of toxin and should be used at high doses for presumptive streptococcal toxin-mediated illness

  • Patients with exposure histories that suggest less common etiologies should have additional therapy targeted to those organisms; antibiotic therapy should then be tailored to culture results

  • Intravenous immunoglobulin for streptococcal necrotizing soft tissue infections

    • Dose: 1 ...

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