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Essentials of Diagnosis
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A rapidly spreading infection involving the fascia of deep muscle
Areas that are often affected
Skin or blunt trauma injury may precede the infection
Patients who are more susceptible are
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General Considerations
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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
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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
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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
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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
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Broad-spectrum antibiotic therapy
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