Gas gangrene infection is severe and can advance quickly. Besides replicating and migrating, the organisms which cause gas gangrene produce poisons known as exotoxins. Exotoxins are capable of liquefying adjacent tissue and inhibiting local defense mechanisms which might normally contain a less virulent infection. As such, the advancing infection of gangrene may simply destroy healthy tissue in its path and spread over the course of hours.
By Dirk J. Bakker, M.D.
For clostridial myositis and myonecrosis or spreading clostridial cellulitis with systemic toxicity (or a presumptive diagnosis of either) the preferred treatment is a combination of hyperbaric oxygen (HBO2), surgery, and antibiotics.
Clostridial Myonecrosis is either an endogenous infection, caused by contamination from a clostridial focus in the body (such as the bowel), or an exogenous infection, mostly in patients with compound and/or complicated fractures with extensive soft tissue injuries after street accidents.
The infection is caused by anaerobic, spore-forming, Gram-positive, encapsulated bacilli of the genus clostridium. More than 150 species of clostridium have been recognized but the most commonly isolated is C. perfringens(95%) either alone or in combination with other pathogenic clostridia, C. novyi (8%), C. septicum (4%), and C. histolyticum, C. fallax, and C. sordelli (1% or less of the infections).
A further subdivision can be made in clostridia that are toxogenic, i.e., C. perfringens, C. septicum, C. novyi, and clostridia that are believed to be only proteolytic, i.e., C. histolyticum, C. bifermentans, C. sporogenes, and C. fallax, which augment an infection by their proteolytic capabilities but do not cause the classical gas gangrene syndrome.
C. tertium, C. sphenoides, and C. sordelli can be considered as contaminants. It is not known if and what these microorganisms add to the disease process. The essential role of alpha-toxin in the pathogenesis of gas gangrene was confirmed by Williamson and Titball, who developed a genetically engineered vaccine against alpha-toxin. This vaccine proved to be of value in animal experiments.
Clostridium perfringens is not a strict anaerobe; it may grow freely in O2 tensions of up to 30mmHg and in a restricted manner in tensions up to 70mmHg.
The complete genome sequence of C. perfringens has been published recently.
The key to understanding the pathophysiology of gangrene is to approach it as a clinical concept, rather than a definitive bacteriologic or pathologic entity.
For the induction of Clostridial Myonecrosis, two conditions have to be fulfilled: 1) The presence of clostridial spores and 2) An area of lowered oxidation-reduction potential caused by circulatory failure in a local area or by extensive soft tissue damage and necrotic muscle tissue. This condition results in an area with a low O2 tension, where clostridial spores can develop into the vegetative form.121
The advantages of hyperbaric oxygen treatment in gas gangrene are two-fold. First, it may be life-saving because exotoxin production is rapidly halted and less heroic surgery may be needed in gravely ill patients. Second, it may be limb and tissue-saving, possibly preventing limb amputation that might otherwise be necessary.