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A 54-year-old woman with diabetes was brought to the emergency department with right leg swelling, fever, and altered mental status.1 The patient noted a pimple in her groin 5 days earlier and over the past few days had increasing leg pain. Her right leg was tender, red, hot, and swollen (Figure 122-1). Large bullae were present. Her temperature was 38.9°C (102°F) and her blood sugar was 573. The skin had a “woody” feel and a radiograph of her leg showed gas in the muscles and soft tissues (Figure 122-2). She was taken to the operating room for debridement of her necrotizing fasciitis. Broad-spectrum antibiotics were also started but the infection continued to advance quickly. The patient died the following day; her wound culture later grew Escherichia coli, Proteus vulgaris, Corynebacterium, Enterococcus, Staphylococcus sp., and Peptostreptococcus.1

Figure 122-1

Necrotizing fasciitis on the leg and groin showing erythema, swelling, and bullae. (From Dufel S, Martino M. Simple cellulitis or a more serious infection? J Fam Pract. 2006;55(5):396-400. Reproduced with permission from Frontline Medical Communications.)

Figure 122-2

Radiograph of the patient's leg showing gas in the soft tissues and muscles. (Courtesy of Susan Dufel, MD.)1

Necrotizing fasciitis (NF) is a rapidly progressive infection of the deep fascia, with necrosis of the subcutaneous tissues. It usually occurs after surgery or trauma. Patients have erythema and pain disproportionate to the physical findings. Immediate surgical debridement and antibiotic therapy should be initiated.2

  • Flesh-eating bacteria, necrotizing soft-tissue infection (NSTI), suppurative fasciitis, hospital gangrene, and necrotizing erysipelas. Fournier gangrene is a type of NF or NSTI in the genital and perineal region.3

  • Incidence in adults is 0.40 cases per 100,000 population.4
  • NF caused by Streptococcus pyogenes is the most common form of NF.4

  • Type I NF is a polymicrobial infection with aerobic and anaerobic bacteria:
    • Frequently caused by enteric Gram-negative pathogens including Enterobacteriaceae organisms and Bacteroides.
    • Can occur with Gram-positive organisms such as non-group A streptococci and Peptostreptococcus.5
    • Saltwater variant can occur with penetrating trauma or an open wound contaminated with saltwater containing marine vibrios. Vibrio vulnificus is the most virulent (Figure 122-3).6
    • Up to 15 pathogens have been isolated in a single wound.
    • Average of five different isolates per wound.7
  • Type II NF occurs from common skin organisms:
    • Generally a monomicrobial infection caused by S. pyogenes:
      • May occur in combination with Staphylococcus aureus.
      • Methicillin-resistant S. aureus is no longer a rare cause of NF.5
      • S. pyogenes strains may produce pyrogenic exotoxins, which act as superantigens to stimulate production of tumor necrosis factor (TNF)-α, TNF-β, interleukin (IL)-1, IL-6, and IL-2.7

Figure 122-3

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