Clostridium tetani

Abstract

More than 100 species of clostridia have now been described. These organisms are widely distributed in the environment, both in soil and in water, and may also colonise the intestinal tract of man and other animals. Clostridium tetani is the causal organism of tetanus, which is an exogenous infection of humans arising as the result of inoculation of spores of the organism at the site of major or minor trauma. The clinical manifestations are entirely the consequence of the action of the potent, plasmid-encoded neurotoxin, tetanospasmin, which is elaborated by the organism and released after autolysis of the cell. This heat-labile protein toxin interferes with the secretion of inhibitory neurotransmitters in motor neurones, resulting in the characteristic prolonged spastic paralysis which is the key feature of the disease. Non-toxigenic, and hence non-pathogenic, isolates lacking the toxin-encoding plasmid can occur. Although the disease is still not uncommon in developing countries, it is entirely preventable by immunisation with inactivated tetanus toxoid.