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Clostridium
Clostridium
INTRODUCTION
Of the anaerobes that infect humans, the clostridia are the most widely studied. They are involved in a variety of human diseases, the most important of which are gas gangrene, tetanus, botulism, pseudomembranous colitis and food poisoning. In most cases, clostridia are opportunistic pathogens; that is, one or more species establishes a nidus of infection in a particular site in a compromised host. All pathogenic clostridial species produce protein exotoxins (such as botulinum and tetanus toxins) that play an important role in pathogenesis.
Most generalizations about Clostridium have exceptions. The clostridia are classically anaerobic rods, but some species can become aerotolerant on subculture; a few species (C carnis, C histolyticum, and C tertium) can grow under aerobic conditions. Most species are Gram-positive, but a few are Gram-negative. Also, many Gram-positive species easily lose the Gram reaction, resulting in Gram-negative cultures.
The clostridia form characteristic spores, the position of which is useful in species identification; however, s ome species do not sporulate unless exposed to exacting cultural conditions. Many clostridia are transient or permanent members of the normal flora of the human skin and the gastrointestinal tracts of humans and animals. Unlike typical members of the human bacterial flora, most clostridia can also be found worldwide in the soil.
Most generalizations about Clostridium have exceptions. The clostridia are classically anaerobic rods, but some species can become aerotolerant on subculture; a few species (C carnis, C histolyticum, and C tertium) can grow under aerobic conditions. Most species are Gram-positive, but a few are Gram-negative. Also, many Gram-positive species easily lose the Gram reaction, resulting in Gram-negative cultures.
The clostridia form characteristic spores, the position of which is useful in species identification; however, s ome species do not sporulate unless exposed to exacting cultural conditions. Many clostridia are transient or permanent members of the normal flora of the human skin and the gastrointestinal tracts of humans and animals. Unlike typical members of the human bacterial flora, most clostridia can also be found worldwide in the soil.
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