Necrotizing fasciitis pathophysiology: Difference between revisions
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*The bacteria or bacterium usually transmitted into the body via | *The bacteria or bacterium usually transmitted into the body via | ||
:*An external injury (surgical sites, a cut, scratch, bruise, boil, or any small injury) | :*An external injury (surgical sites, a cut, scratch, bruise, boil, or any small injury) | ||
:*Direct spread from a punctured / perforated internal organ (particularly the colon, rectum, or anus) | :*Direct spread from a punctured / perforated internal or sexual organ (particularly the colon, rectum, or anus) | ||
:*Sexual | :*Sexual | ||
*Following transmission, the bacteria or bacterium spreads via the fascia, producing [[exotoxins]] and [[endotoxins]]. | *Following transmission, the bacteria or bacterium spreads via the fascia, producing [[exotoxins]] and [[endotoxins]]. | ||
*These toxins restricts blood supply to tissues ([[ischemia]]) leading to digestion of cells by enzymes resulting in a lesion consisting of pus and the fluid remains of dead tissue. | *These toxins restricts blood supply to tissues ([[ischemia]]) leading to digestion of cells by enzymes resulting in a lesion consisting of pus and the fluid remains of dead tissue. | ||
* | *As the blood supply to these tissues is impaired, neither antibiotics nor the body’s own mechanisms to fight infection are able to reach these tissues. | ||
'''Type 1 necrotizing fasciitis''' ('''Synergistic NF''') | '''Type 1 necrotizing fasciitis''' ('''Synergistic NF''') | ||
Revision as of 19:50, 30 August 2016
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Yamuna Kondapally, M.B.B.S[2]
Overview
Pathophysiology
All types of necrotizing fasciitis have common pathophysiology but the speed of development and associated clinical features may differ depending on the causative organisms.
- The bacteria or bacterium usually transmitted into the body via
- An external injury (surgical sites, a cut, scratch, bruise, boil, or any small injury)
- Direct spread from a punctured / perforated internal or sexual organ (particularly the colon, rectum, or anus)
- Sexual
- Following transmission, the bacteria or bacterium spreads via the fascia, producing exotoxins and endotoxins.
- These toxins restricts blood supply to tissues (ischemia) leading to digestion of cells by enzymes resulting in a lesion consisting of pus and the fluid remains of dead tissue.
- As the blood supply to these tissues is impaired, neither antibiotics nor the body’s own mechanisms to fight infection are able to reach these tissues.
Type 1 necrotizing fasciitis (Synergistic NF)
- Comparatively slow process
- It is commonly seen in immunocompromised or those with underlying abdominal pathology
- Synergistic NF develops following complicated abdominal surgery, ischiorectal or perineal abscesses when the gut flora breaches the mucosa entering tissue planes.
“Flesh-eating bacteria” is a misnomer, as the bacteria do not actually eat the tissue. They cause the destruction of skin and muscle by releasing toxins (virulence factors). These include streptococcal pyogenic exotoxins and other virulence factors. S. pyogenes produces an exotoxin known as a superantigen. This toxin is capable of activating T-cells non-specifically. This causes the over-production of cytokines that over-stimulate macrophages. The macrophages cause the actual tissue damage by releasing oxygen free radicals that are normally intended to destroy bacteria but are capable of damaging nearly any macromolecule they contact in the body.