Clostridium tetani

Clostridium tetani is a bacterium of the genus Clostridium. It is found in nature as spores in soil or parasitising the gastrointestinal tracts of animals, and causes serious toxicity in humans. Like other Clostridium species, it is Gram-positive, and its appearance on a gram stain is said to resemble tennis rackets or drumsticks.

History

Tetanus was known to ancient peoples, who recognized the relationship between wounds and fatal muscle spasms. In 1884, the strychnine-like toxin of tetanus was isolated from free-living, anaerobic soil bacteria. In 1890, tetanus toxoid was developed, providing active immunization against the illness. This is our modern tetanus vaccine.

Characteristics

C. tetani is an obligately anaerobic bacillus that stains gram positive in fresh cultures, but may stain gram negative in older cultures. During growth, the germ possesses many flagella and have limited mobility. Two toxins are elaborated, tetanospasmin and tetanolysin, the latter of which is of uncertain toxicity and significance. As the organism matures, it develops a terminal spore, giving it the characteristic tennis racket appearance. Spores are extremely hardy but can be rendered harmless by iodine, hydrogen peroxide or heat and pressure treatment (autoclaving). From a clinical viewpoint, growing the organism from a wound is of no significance.

Epidemiology

There are about one million cases of tetanus reported worldwide and about 70 in the United States annually. Most cases in the US are in the elderly who have allowed their innoculations to lapse, whereas most cases in developing countries are in newborns.Its most common Victims are Animal and Humans

Toxicity

Tetanospasmin is similar in structure to botulinum toxin, but very different in effect. It is a zinc-dependent metalloproteinase. There is a heavy protein chain and a light chain connected by a disulfide bridge. The heavy chain attaches to the cellular receptor, and the light chain produces the toxic effects. It enters the central nervous system by binding to the ends of axons and travelling up the axon to the cell bodies. There, it blocks the release of neurotransmitter from inhibitory neurons to motor cells. The motor neurons then fire because of unopposed action of excitatory neurons, leading to diffuse muscle spasms.

Signs and Symptoms

Patients with tetanus present: Muscle Spasms, especially in the muscle of the jaw (trimus or lockjaw) Grotesque grinning expression (risus Sardonicus) which is due to spasms of the facial muscles. NB: The mortality is high once the stage of lock-jaw has been reached.

Treatment

Prophylaxis: Prevention of tetanus includes vaccination(DPT), and cleaning the primary wound. DTP ( diphteria-pertussis-tetanus)vaccine, in North America, is given at ages 2, 4,6, and 8 months, followed by a booster before entry to school (4-6 years). This regimen provides protection from tetanus (along with diphteria and pertussis) for about 10 years. So, booster shots of tetanus are to be given every 10 years.

Acute Treatment of Tetanus: Tetanus can be treated by using penicillin. Muscle relaxants may need to be administered. Tetanus can lead to respiratory failure requiring mechanical ventilation.

References

Clinical Microbiology, ISBN 0940780496

Clostridiaceae