Which bacterium causes tetanus, the disease marked by painful muscle spasms?

Clostridium tetani causes tetanus, a disease marked by painful muscle spasms.

This bacterium is an anaerobic, spore-forming member of the genus Clostridium. Its spores are common in soil and can enter the body through puncture wounds, burns, animal bites, or other injuries. The bacterium produces tetanospasmin, a powerful neurotoxin that disrupts inhibitory nerve signals.

Tetanus does not usually spread directly from person to person. The characteristic jaw stiffness is called trismus, which explains the common name “lockjaw.” Muscle spasms can spread from the jaw and neck to the trunk and limbs, while the person’s awareness is generally preserved.

Vaccination uses a detoxified form of the toxin called tetanus toxoid. Booster doses are recommended because protection can decline over time. A common mix-up is with Clostridium botulinum: it causes botulism, whose toxin produces a different pattern dominated by flaccid paralysis.