C. perfringens is a large, Gram-positive, nonmotile rod with square ends. It growsovernight on blood agar medium under anaerobic conditions, producing colonies sur-rounded by a double zone of hemolysis (Fig 19 – 2). In broth containing fermentable car-bohydrate, growth of C. perfringens is accompanied by the production of large amounts of hydrogen and carbon dioxide gas, which can also be produced in necrotic tissues; hence the term gas gangrene.
C. perfringens produces multiple exotoxins that have different pathogenic signifi-cance in different animal species and serve as the basis for classification of the five types (A to E). Type A is by far the most important in humans and is found consistently in the colon and often in soil.
The most important exotoxin is the α-Toxin, a phospholipase that hydrolyzes lecithin and sphingomyelin, thus disrupting the cell membranes of various host cells, including erythrocytes, leukocytes, and muscle cells. The α-Toxin alters capil-lary permeability and is toxic to heart muscle. This pore-forming toxin is closely related to streptolysin O . When the enterotoxin is attached to enterocyte mem-branes, it causes an increase in intracellular calcium and altered membrane permeability which leads to loss of cellular uid and macromolecules.
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