Tetanus is caused by which bacterium?

• A. Clostridium tetani
• B. Clostridium botulinum
• C. Staphylococcus aureus
• D. Escherichia coli

Answer: (A)

Tetanus is caused by a toxin produced by Clostridium tetani, an obligate anaerobe that forms spores and is commonly found in soil. When its spores enter a wound with low oxygen, they germinate and release tetanospasmin, which travels to the nervous system and blocks the release of inhibitory neurotransmitters like GABA and glycine. This loss of inhibition leads to unregulated motor neuron activity, resulting in the muscle rigidity and spasms characteristic of tetanus. The other bacteria listed do not produce this toxin or cause tetanus: Clostridium botulinum makes botulinum toxin and leads to botulism, while Staphylococcus aureus and Escherichia coli are associated with other infections. Vaccination with tetanus toxoid provides immunity and is a key preventive measure.