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Concept
Clostridium novyi
Résumé
Clostridium novyi (oedematiens) a Gram-positive, endospore- forming, obligate anaerobic bacteria of the class Clostridia. It is ubiquitous, being found in the soil and faeces. It is pathogenic, causing a wide variety of diseases in man and animals.
Growth in culture proceeds through 3 stages: Initial growth wherein no toxin is produced; vigorous growth wherein toxin is produced; and spore formation wherein endospores are formed and toxin production decreases. It is suggested that type C may be type B that forms spores more readily so does not go through the toxin-production stage.
Isolating and identifying C novyi is difficult due to its extreme anaerobic nature. Commercial kits may not be adequate.
It is also fastidious and difficult to culture, requiring the presence of thiols.
Clostridium novyi is considered to be made up from three clades, labelled A, B and C, distinguished by the range of toxins they produce. While strains of type C were not linked to disease to laboratory animals, presence and activity of toxins in C. novyi have been linked to infection with Bacteriophages.
Based on toxin production, Clostridium haemolyticum has been suggested to be considered a part of C. novyi, forming a separate type D in the genus. More recent 16S-rDNA studies however have suggested, that C. haemolyticus and types B and C of C. novyi may form a distinct genus, closely related to Clostridium botulinum type C and D, instead.
The toxins are designated by Greek letters. The toxins normally produced by the various types are shown in table 1
The alpha-toxin of Clostridium botulinum types C and D, is similar to the C novyi beta-toxin.
The A and B toxins of Clostridium difficile show homology with the alpha-toxin of C novyi as does the lethal toxin of clostridium sordellii.
The alpha-toxin is characterised as lethal and necrotizing.
The type A alpha-toxin is oedematising. It acts by causing morphological changes to all cell types especially endothelial cells by inhibition of signal transduction pathways, resulting in the breakdown of cytoskeletal structures.
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