Clostridium tetani is –
**Core Concept**
Clostridium tetani is a gram-positive, anaerobic, spore-forming bacterium that produces a potent neurotoxin responsible for tetanus infection. This bacterium is commonly found in soil and can enter the body through wounds or cuts.
**Why the Correct Answer is Right**
Tetanus toxin, also known as tetanospasmin, is a zinc-dependent metalloprotease that blocks the release of neurotransmitters glycine and GABA from the presynaptic neuron. This results in an increase in excitatory neurotransmitters and a decrease in inhibitory neurotransmitters, leading to muscle rigidity, spasms, and rigidity. The toxin affects the central nervous system, causing the characteristic symptoms of tetanus.
**Why Each Wrong Option is Incorrect**
**Option A:** This option might describe Clostridium perfringens, another gram-positive, anaerobic bacterium that produces toxins causing gas gangrene and food poisoning.
**Option B:** This option might describe Clostridium difficile, a gram-positive, anaerobic bacterium that causes antibiotic-associated diarrhea and colitis.
**Option C:** This option might describe Clostridium botulinum, a gram-positive, anaerobic bacterium that produces a toxin causing botulism.
**Clinical Pearl / High-Yield Fact**
Tetanus toxin is heat-labile, and proper wound cleaning and debridement can prevent tetanus infection. The vaccine against tetanus is effective against the toxin, but booster shots are required every 10 years to maintain immunity.
**Correct Answer:** D. Clostridium tetani.