Last updated on April 24, 2014 at 6:16 EDT

Clostridium tetani

Clostridium tetani is a rod-shaped, anaerobic bacterium of the genus Clostridium. It’s a gram-positive and resembles tennis rackets or drumsticks on a gram stain. It can be found as spores in soil and the gastrointestinal tract of animals. It produces a potent biological toxin which is the causative agent of tetanus.

Ancient people recognized the relationship between wounds and fatal muscle spasms. Arthur Nicolaier isolated tetanus from soil bacteria. Antonie Carl and Giorgio Rattone studied more of the etiology of the disease in 1890. They produced tetanus in rabbits from a case of human tetanus. Later they found that the toxin could be neutralized by specific antibodies.

The tetanus antitoxin induced passive immunity in humans and could be used for prophylaxis and treatment. P. Descombey developed the tetanus toxoid vaccine in 1924.

During the vegetative growth state the organism can’t survive in the presence of oxygen. It is heat-sensitive and exhibits flagellar motility. The older it gets the bacteria will develop a terminal spore that gives the organism its appearance. The spores are extremely hardy since they are resistant to heat and most antiseptics.

Tetanus is prevented through the use of an effective vaccine. Severe reactions are rare and can include anaphylaxis, seizures and encephalopathy. Generally these are thought to occur if the tetanus-diphtheria component of the vaccine is given. Vaccines are recommended for all infants at the age of 2, 4, 6, and 15 months of age. Between ages 4 and 6 a fifth booster should be given. A new shot should be given every 10 years after that.

C. tetani enters the host through a wound in the skin and then proceeds to replicate. Once infection is established, C. tetani will make two exotoxins: tetanolysin and tetanospasmin. There are eleven strains that have been identified. The toxin producing genes are encoded on a plasmid that is present in all toxigenic strains. Based on weight, tetanospasmin is on e of the most potent toxins known. 2.5 nanograms per kilogram of body weight is the estimated lethal dose for a human.

The blood and lymphatic system distribute tetanospsmin in the host. It attacks at several sites within the nervous system, including peripheral nerve terminals, the brain, the spinal cord, and within the symphatic nervous system.

Clinical manifestations of tetanus happen when the toxin blocks inhibitory impulses. This leads to muscle contraction and spasm, trismus (or “lock-jaw”), and opisthotonus. Seizures can occur and the autonomic nervous system can be affected.

Clostridium tetani