Tetanus
Tetanus is a rare disease in the United States, with only about 40–50 cases reported each year. Tetanus is caused by an exotoxin produced by Clostridium tetani, an anaerobic, spore-forming, gram-positive rod found widely in soil and in the GI tract. Tetanus typically is seen in older persons (especially older women), recent immigrants, and IV drug users who have not maintained adequate tetanus immunization.
Mechanism of toxicity. The growth of C tetani in a wound under anaerobic conditions produces the toxin tetanospasmin. The toxin enters the myoneural junction of alpha motor neurons and travels by retrograde axonal transport to the synapse. There, it blocks the release of the presynaptic inhibitory neurotransmitters gamma-aminobutyric acid (GABA) and glycine, causing intense muscular spasms.
Toxic dose. Tetanospasmin is an extremely potent toxin. Fatal tetanus can result from a minor puncture wound in a susceptible individual.
Clinical presentation. The incubation period between the initial wound and the development of symptoms averages 1–2 weeks (range, 2–56 days). The wound is not apparent in about 5% of cases. Wound cultures are positive for C tetani only about one-third of the time.
The most common initial complaint is pain and stiffness of the jaw, progressing to trismus, risus sardonicus
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