Necrotizing soft tissue infections are rare, serious, and sometimes life-threatening bacterial infections. Necrotizing fasciitis, or flesh-eating disease, is the most widely known infection of this type. Necrosis means the death of cells and tissue. Skin, muscle, and connective tissue infected with bacteria may suffer hypoxia, or a lack of oxygen, and die.
Flesh-eating disease may be caused by a number of different bacteria, in a single strain or mixed, originating within the body, in chronic or traumatic wounds, or from foreign matter.
The most common risk factors associated with necrotizing fasciitis are traumatic breaks in the skin, most commonly lacerations, insect bites, burns, deep abrasions, puncture wounds, or following surgery, particularly those involving bowel perforations.
Diabetes appears to be a strong risk factor, as are obesity, alcoholism, smoking, and intravenous drug abuse. Reports of necrotizing fasciitis as a result of infection of otherwise typical lesions of chickenpox have been published.
An association with the use of non-steroidal anti-inflammatory agents has also been suggested. NSAIDs are cyclo-oxygenase inhibitors and may have an adverse effect on neutrophil killing and cell-mediated immunity. NSAIDs are reported to inhibit monocyte superoxide production.
Most common sites of occurrence of necrotizing fasciitis are the lower extremities, while an increased incidence in the upper extremities is seen in the parenteral drug abuse population.
However, any location of the body can be affected, including the abdominal wall of neonates, in association with omphalitis. Involvement of the scrotum and perineum in the male is known as Fournier's Gangrene, which is essentially necrotizing fasciitis of the superficial perineal fascia, also known as Colles' fascia; which can spread infection to the penis and scrotum via Buck's fascia or Dartos' fascia; or Scarpa's fascia, which connects to, and can spread infection to, the abdominal wall.
Perianal or perirectal infection may also spread into these areas, and undrained or inadequately drained perirectal abscesses are often cited as a source of Fournier's Gangrene. Perineal necrotizing fasciitis can also occur in the female.
Diabetes mellitus remains a strong risk factor in this particular form of necrotizing fasciitis as well. Fournier's Gangrene is more likely to have multiple mixed organisms cultured, particularly Enterobacteriaceae, Group D streptococci, and anaerobic organisms, such as Bacteroides fragilis.