Necrotizing infections Flashcards
Describe necrotizing infections:
1. What part of the body do these infections involve?
2. Why are they devastating?
3. How do they occur?
Necrotizing SSTIs have a much worse clinical presentation, coexisting systemic manifestations, and more aggressive treatment strategies.
1. These deep infections involve the fascial and/or muscle compartments
2. and are devastating as they can cause significant removal of tissue via debridement or even cause death.
3. As with other SSTIs, they usually develop from an initial break in the skin related to trauma or surgery. They can be monomicrobial or polymicrobial.
What is necrotizing fasciitis?
is an aggressive subcutaneous infection that affects the superficial fascia, which comprises all the tissue between the skin and underlying muscles. Extension from a skin lesion is seen in most cases.
The initial lesion may be minor, such as a minor abrasion, insect bite, injection site (as in drug addicts), or boil, and a small minority of patients have no visible skin lesion. During my residency, a patient came down with NF after a tennis ball hit her in the arm!
Describe the clinical course of NF?
NF starts out looking like cellulitis, which progresses rapidly. As it advances, there is systemic toxicity, often including high temperatures, disorientation, and lethargy. I have been told that the pain from it is disproportionate to what the infection looks like. Examination of the infection site reveals inflammation, edema, and discoloration or gangrene and anesthesia of the skin. A distinguishing clinical feature is the wooden-hardness subcutaneous tissues. In cellulitis, the subcutaneous tissues are visible and yielding. In NF the underlying tissues are firm, and examination by touching is difficult. Bullae may also form. Surgical debridement is the definitive way to diagnose NF.
What is the distinguishing feature of NF?
A distinguishing clinical feature is the wooden-hardness subcutaneous tissues. In cellulitis, the subcutaneous tissues are visible and yielding. In NF the underlying tissues are firm, and examination by touching is difficult. Bullae may also form.
What is the difinitive way to diagnose NF?
Surgical debridement
Describe Type 1 AKA polymicrobia NF?
1. Who does it occur in?
2. What type of bacteria are involved?
3. How fast is its spread?
- Polymicrobial or Type I generally occurs after trauma or surgery and in injection drug users.
- B mix of anaerobes (Bacteroides, Peptostreptococcus) and facultative bacteria (streptococci and Enterobacteriaceae) that act synergistically to cause destruction of fat and fascia.
- In type I infections, the skin may be spared, and the speed at which the infection spreads (3-5 days) is slightly slower than that in type II.
- What bacteria is implicated in Type 2 or monomicrobial NF?
- Is it fast, or slow evolving?
- What is Type 2 associated with?
- Monomicrobial or Type II necrotizing fasciitis is caused by virulent strains of S. pyogenes and is what patients will know as flesh eating disease.
- It differs from type I infections in that it evolves rapidly (24-72 hours) and has extensive necrosis of subcutaneous tissues and skin, as well as gangrene, severe local pain, and systemic symptoms.
- It is also highly associated with an early onset of shock and organ failure and are present in approximately half the cases of streptococcal toxic shock-like syndrome.
What is the definitive treatment that must be used for NF?
Immediate and significant surgical debridement must occur upon diagnosis of NF.
What antibiotics are used for:
1. Type 1 (polymicrobial)
2. Type 2 (Monomicrobial)
- Polymicrobial (anaerobes, and facultative bacteria) - Pip/taz PLUS vanco
- Monomicrobial (S. Pyogenes) - Penicillin plus clindamycin
Why is the addition of clindamycin recommended for type 2 NF?
The addition of clindamycin may cause decreased production of bacterial exotoxins, and it will also cover S. pyogenes from an antimicrobial perspective. Finally, clindamycin may have immunomodulatory properties that assists in making a positive outcome more likely.
