Medical Bacteriology- Lecture 10
Clostridia
, Clostridium
• large, Gram-positive- rodshaped - All species form endospores
• strictly fermentative type of metabolism (Most clostridia will not grow under aerobic conditions and
vegetative cells are killed by exposure to O2, but their spores are able to survive long periods of
exposure to air)
• live in all of the anaerobic habitats of nature, including soils, aquatic sediments and the intestinal tracts
of animals.
• Clostridia are able to ferment a wide variety of organic compounds. They produce end products such as
butyric acid, acetic acid, butanol & acetone, and large amounts of gas (CO2 and H2) during fermentation
of sugars.
• A variety of foul smelling compounds are formed during the fermentation of amino acids and fatty acids
• The clostridia produce a wide variety of extracellular enzymes to degrade large biological molecules
(e.g. proteins, lipids, collagen, cellulose, etc.) in the environment. Hence, the clostridia play an importan
role in nature in biodegradation and carbon cycle. In anaerobic clostridial infections, these enzymes pla
a role in invasion and pathology.
• Most of the clostridia are saprophytes
• a few are pathogenic for humans; Clostridium perfringens, C. difficile & C. tetani (saprophytic in nature
and, in a sense, are opportunistic pathogens.
• Clostridium tetani (tetanus) & Clostridium botulinum (food-borne botulism) produce the most potent
biological toxins known to affect humans.
• Other clostridia, however, are highly invasive under certain circumstances.
Clostridia
, Clostridium
• large, Gram-positive- rodshaped - All species form endospores
• strictly fermentative type of metabolism (Most clostridia will not grow under aerobic conditions and
vegetative cells are killed by exposure to O2, but their spores are able to survive long periods of
exposure to air)
• live in all of the anaerobic habitats of nature, including soils, aquatic sediments and the intestinal tracts
of animals.
• Clostridia are able to ferment a wide variety of organic compounds. They produce end products such as
butyric acid, acetic acid, butanol & acetone, and large amounts of gas (CO2 and H2) during fermentation
of sugars.
• A variety of foul smelling compounds are formed during the fermentation of amino acids and fatty acids
• The clostridia produce a wide variety of extracellular enzymes to degrade large biological molecules
(e.g. proteins, lipids, collagen, cellulose, etc.) in the environment. Hence, the clostridia play an importan
role in nature in biodegradation and carbon cycle. In anaerobic clostridial infections, these enzymes pla
a role in invasion and pathology.
• Most of the clostridia are saprophytes
• a few are pathogenic for humans; Clostridium perfringens, C. difficile & C. tetani (saprophytic in nature
and, in a sense, are opportunistic pathogens.
• Clostridium tetani (tetanus) & Clostridium botulinum (food-borne botulism) produce the most potent
biological toxins known to affect humans.
• Other clostridia, however, are highly invasive under certain circumstances.
