Clostridia are prokaryotic bacteria of the phylum Firmicutes, which are large, anaerobic, spore-forming, rod-shaped, gram-positive organisms. They can be living cells (vegetative forms) or dormant spores. Their natural habitats are soils and intestinal tracts of animals, including humans.
Dormant spores of several clostridial species have been found in healthy muscular tissue of horses and cows. The endospores are oval, sometimes spherical, and are located centrally, subterminally, or terminally. The vegetative forms of clostridia in tissue fluids of infected animals occur singly, in pairs, or rarely in chains.
Differentiation of the various pathogenic and related species is based on morphological characteristics in culture including spore shape and position, biochemical testing, and the antigenic specificity of toxins or surface antigens. The genomes of many clostridial spp have been sequenced and published. Pathogenic strains or their toxins may be acquired by susceptible animals via either wound contamination or ingestion. Diseases thus produced are a constant threat to successful food animal production worldwide.
Clostridial diseases can be divided into two categories:
those in which the organisms actively invade or when locally dormant spores are activated and reproduce in tissues of the host, with the production of toxins that enhance the spread of infection (the gas-gangrene group, the clostridial cellulitides group)
those characterized by toxemia resulting from the absorption of toxins produced by organisms within the digestive system (the enterotoxemias Enterotoxemias in Animals Type A strains of C perfringens are commonly found as part of the normal intestinal microflora of animals and lack some of the powerful toxins produced by strains of other types. C... read more ), in devitalized tissue (tetanus Tetanus in Animals Tetanus is caused by the neurotoxin produced by Clostridium tetani , which is found in soil and intestinal tracts and usually introduced into tissues through deep puncture wounds. The... read more ), or in food or carrion outside the body (botulism Botulism in Animals Botulism most commonly results from ingestion of toxin in food. The usual source of the toxin is decaying carcasses or vegetable material. Clinical signs are caused by flaccid muscle paralysis... read more )
Clostridial diseases are not spread from animal to animal or from animals to humans. They have been classified into three forms: