Clostridia are relatively large, gram-positive, rod-shaped bacteria that can undergo only anaerobic metabolism. Most Clostridia cannot grow under aerobic conditions and even can be killed by exposure to O2, but they form endospores that are able to survive long periods of exposure to air and other adverse environmental conditions. The natural sources of Clostridia are anaerobic habitats with organic nutrients, particularly soils, aquatic sediments and the intestinal tracts of animals. Their fermentation of organic compounds, like sugars, produces large amounts of CO2 and H2 as well as volatile organic compounds like acetic and butyric acid, acetone and butanol. Metabolism of substrates like amino acids and fatty acids results in foul-smelling degradation products. Clostridia also have an extended range of extracellular enzymes that degrade large biological molecules in the environment into fermentable compounds. Although there are non-pathogenic Clostridia, this genus produces some of the most potent biological toxins. Three particularly bad actors in this group are C. perfringens, which is responsible for cooked meat-associated food poisoning and wound and surgical infections that lead to gas gangrene, and C. tetani, which is responsible for deadly tetanus infections, and C. botulinum, which causes botulism.
Below are the most well-known pathogenic Clostridia species with their typical properties and occurrence:
Identification of Clostridia is an important first step toward the control and eradication of this potent pathogen. To aid in the diagnosis, Sigma-Aldrich has developed a broad range of selective media (Table 1), tests (Tables 2 and 3) and anaerobic equipment (Table 4) for the detection, identification and differentiation of Clostridia.
Table 3. Gram staining kit and single solutions
Table 4. Anaerobic equipment
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