What is Clostridium Tetani?

Clostridium tetani is a mobile rod-shaped single-celled anaerobic (can't grow in oxygen) bacterium that is a member of the Clostridium genus. There are eleven known strains and each one produces a potent toxin called tetanospasmin which causes tetanus, a medical condition characterised by abnormal heart rate and blood pressure, excessive sweating, difficulty breathing and swallowing, and muscle spasms in the jaw and other parts of the body. It can be fatal if not treated.

The only known biological toxins that are more dangerous to humans are botulinum (produced by the closely related Clostridium botulinum) and the toxin produced by Corynebacterium diphtheriae that causes diphtheria.

When the spores of C. tetani germinate they produce two toxins - tetanolysin and tetanospasmin. Tetanolysin is a hemolysin which means it causes lysis of red blood cells. But other than that very little is known about it including whether it contributes to the pathogenicity of tetanus. Although many scientists believe that it plays no role in tetanus infection.

It is not the bacterium that cause tetanus symptoms, but the neurotoxin it produces. The toxin is created when spores germinate and vegetative cells grow after gaining access to a wound. It is only released when the bacterial cell lysis. The bacteria multiply locally, but the symptoms occur in remote areas from the infection site. The toxin travels in the bloodstream and lymphatic system and initially binds to peripheral nerve terminals; it's taken up by the axon body and travels across synaptic junctions to the central nervous system where it wreaks its havoc.

Once the toxin has been synthesised it can take between 2 and 14 days to reach the spinal cord.

The neurotoxin tetanospasmin blocks the release of some neurotransmitters, including glycine and gamma-amino butyric acid. Ordinarily these would inhibit some nerve impulses, but the effects of their inhibition are the generalized muscle spasms characteristic of tetanus infection.

The bacterium Clostridium tetani was first isolated by German physician Arthur Nicolaier in 1884. In that same year Antonio Carle and Giorgio Rattone demonstrated its transmissibility. They produced tetanus-like symptoms in rabbits by injecting them with pus from a person who had died from the illness.

In 1889 Kitasato Shibasaburo found that the effects of the condition could be neutralized by antibodies against tetanospasmin. And towards the end of the nineteenth century the French microbiologist and veterinarian Edmond Nocord demonstrated that tetanus antitoxin could be used as the basis for tetanus treatment and prevention.