TETANUS

MICROBIOLOGY, EPIDEMIOLOGY, AND PATHOGENESIS

Tetanus is characterized by increased muscle tone and spasms caused by tetanospasmin (“tetanus toxin”), a toxin produced by Clostridium tetani.

C. tetani is a spore-forming, anaerobic gram-positive rod that is ubiquitous in soil and whose spores are highly resilient.
Tetanus is a rare disease in the developed world: 26 cases were reported in the United States in 2013. Most cases occur in incompletely vaccinated or unvaccinated individuals.
After spores contaminate wounds (typically puncture wounds or, in the case of neonates, the umbilical stump) and reach a suitable anaerobic environment (e.g., devitalized tissue), organisms proliferate and release toxin.
- The toxin blocks release of inhibitory neurotransmitters (glycine and γ-aminobutyric acid) in presynaptic terminals, and rigidity results from an increased resting firing rate of the α-motor neurons.
- A toxin dose as low as 2.5 ng/kg can be fatal.

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