Anaerobic and Necrotizing Infections
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- Necrotizing soft tissue infections (NSTI) are rare and rapidly progressing infections involving any layer of soft tissue, including skin, subcutaneous fat, fascia, and/or muscle (1).
- NSTI can affect any part of the body but are more commonly seen in extremities and abdominal wall (1).
- NSTI are associated with extensive tissue destruction, systemic toxicity, limb loss and are potentially fatal.
- NSTI represent a medical emergency. Early diagnosis, prompt surgical consultation, and initiation of broad-spectrum antibiotics are essential in improving outcomes (2).
- Associated terms: necrotizing fasciitis, progressive bacterial synergistic gangrene, synergistic necrotizing cellulitis, gas gangrene, nonclostridial anaerobic cellulitis, Fournier gangrene, Ludwig angina, “flesh-eating” infections
- Predominant age: any age
- Predominant sex: male = female
- 4 per 100,000
- Increased incidence in patients >50 years
Etiology and Pathophysiology
- Type I NSTI—most common
- Type II NSTI
- Type III NSTI
- Vibrio vulnificus—associated with exposure to marine environments, especially in patients with severe liver disease
- Aeromonas hydrophila—associated with exposure to freshwater environments
- Clostridium perfringens
- Bacteria enter the soft tissue after trauma causing skin or mucosal breach. Bacterial invasion may also occur without definite site of entry in a host with transient bacteremia after deep tissue trauma (2).
- Bacterial toxins and surface proteins cause a local inflammatory response. Vascular occlusion follows leading to deep tissue ischemia and necrosis (2).
- Bacterial toxins may trigger a systemic inflammatory response, leading to multiorgan failure or sepsis (2).
- Can occur in young, healthy persons without risk factors
- Predisposing risk factors (3)
- Advanced age
- Diabetes, cirrhosis, end-stage renal failure
- Immune suppression (HIV, malignancies, alcoholism, corticosteroid use)
- History of cellulitis or impaired venous and lymphatic drainage (4)
- Peripheral vascular disease
- Precipitating risk factors
- IV drug abuse
- Trauma, burns
- Skin ulceration
- Herpes zoster
- Human, animal, or insect bites (4)
- Surgical risk factors
- Prior operations