Necrotizing Soft Tissue Infections
Basics
Description
Description
- Necrotizing soft tissue infections (NSTI) are infections of any layer of the skin and soft tissue associated with necrotizing changes
- Includes cellulitis, fasciitis, and myositis
- Usually spreads rapidly along tissue planes
- Characterized as a group by:
- Widespread fascial and muscle necrosis with relative sparing of the skin
- High mortality
- Systemic toxicity
- Necrotizing cellulitis:
- Crepitus and gas of skin
- Spares deeper structures
- May lack systemic toxicity
- Necrotizing fasciitis:
- Classic, historical name (and often inaccurate description) for most NSTIs
- Progressive, rapidly spreading infection with extensive dissection and necrosis of the fascia and subcutaneous (SC) fat
- Frequently spares skin and muscle initially
- Fournier gangrene:
- Mixed aerobic–anaerobic NSTI of the perineum
- CDC reports 500–1,500 cases per yr in the U.S.
- Often difficult to recognize initially
- Risk factors include:
- Advanced age
- Chronic systemic disease:
- Diabetes
- Obesity
- Peripheral vascular disease
- Renal failure
- Smoking
- Alcohol abuse
- IV drug abuse
- Immunosuppression
- Recent surgery
- Traumatic wounds
- 14–40% mortality
- High morbidity:
- Frequent need for amputations
- Renal failure, cardiomyopathy, multisystem organ dysfunction
Etiology
Etiology
- Conditions that lead to the development of NSTIs:
- Most from local tissue trauma with bacterial invasion
- Less frequently from local ischemia or nonpenetrating trauma and reduced host defenses as above
- Type I NSTI:
- Polymicrobial, including at least 1 anaerobe
- Anaerobic and aerobic bacteria
- Includes Fournier gangrene
- Seen more in elderly, those with underlying illnesses, or after recent surgery
- Represent majority of NSTIs
- Streptococcal species are most common aerobes
- Also Staphylococcus, Enterococcus, Escherichia coli, Klebsiella
- Bacteroides are most common anaerobes
- Type II NSTI:
- Monomicrobial
- Most commonly group A Streptococcus
- Staphylococcus aureus including methicillin-resistant S. aureus (MRSA) second most common
- Often young, healthy patients
- Almost half with no skin portal of entry
- Often no gas seen on imaging
- Approximately half of group A strep vs Strep - group A strep is multiple places in the text and the rest are lower case cases associated with streptococcal toxic shock syndrome
- Predisposing factors include skin injury, IV drug use, surgery, childbirth
- Type III NSTI:
- Less common NSTI (<5%)
- Rapidly progressive
- Includes infections from Clostridium, Vibrio, Aeromonas, and gram-negative bacteria
- Usually following penetrating wounds, crush injuries, or aquatic exposure
- Type IV NSTI: (Rare)
- Fungal etiology including Candida and Zygomycetes
- Occurs in immunocompromised
- Microbes involved include:
- Group A β-hemolytic Streptococcus (GABHS)
- Group B Streptococcus
- Staphylococcus
- Enterococcus
- Bacillus
- Pseudomonas
- E. coli
- Proteus
- Klebsiella
- Enterobacter
- Bacteroides
- Pasteurella
- Clostridium
- Vibrio vulnificus
- Aeromonas hydrophila
- Candida
- Zygomycetes
Pediatric Considerations
- Risk factors for neonates:
- Omphalitis
- Minor surgeries: Circumcision, hernia
- Risk factors for children:
- Chronic illness
- Surgery
- Recent varicella infection
- Congenital and acquired immunodeficiencies
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Citation
Schaider, Jeffrey J., et al., editors. "Necrotizing Soft Tissue Infections." 5-Minute Emergency Consult, 6th ed., Lippincott Williams & Wilkins, 2020. Emergency Central, emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307316/all/Necrotizing_Soft_Tissue_Infections.
Necrotizing Soft Tissue Infections. In: Schaider JJJ, Barkin RMR, Hayden SRS, et al, eds. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2020. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307316/all/Necrotizing_Soft_Tissue_Infections. Accessed November 14, 2024.
Necrotizing Soft Tissue Infections. (2020). In Schaider, J. J., Barkin, R. M., Hayden, S. R., Wolfe, R. E., Barkin, A. Z., Shayne, P., & Rosen, P. (Eds.), 5-Minute Emergency Consult (6th ed.). Lippincott Williams & Wilkins. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307316/all/Necrotizing_Soft_Tissue_Infections
Necrotizing Soft Tissue Infections [Internet]. In: Schaider JJJ, Barkin RMR, Hayden SRS, Wolfe RER, Barkin AZA, Shayne PP, Rosen PP, editors. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2020. [cited 2024 November 14]. Available from: https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307316/all/Necrotizing_Soft_Tissue_Infections.
* Article titles in AMA citation format should be in sentence-case
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