What organism causes tetanus?

• A. Bacillus anthracis
• B. Clostridium tetani
• C. Vibrio cholerae
• D. Clostridium botulinum

Answer: (B)

Tetanus is caused by Clostridium tetani, an anaerobic, spore-forming bacterium found in soil. When its spores enter a wound and germinate in low-oxygen conditions, they release tetanospasmin, a powerful neurotoxin. This toxin blocks the release of inhibitory neurotransmitters in the spinal cord, leading to unregulated motor neuron activity and the characteristic muscle rigidity and lockjaw. Tetanus is not spread from person to person, and vaccination with tetanus toxoid provides protection.

For contrast, Bacillus anthracis causes anthrax, Vibrio cholerae causes cholera, and Clostridium botulinum causes botulism, which presents with flaccid paralysis rather than the spastic paralysis seen in tetanus.