Compare and contrast the pathogenicity of Clostridium botulinum and Clostridium tetani, including mechanisms of action of their toxins and disease manifestations

Question

What will be an ideal response?

Answer 1

Both bacteria are anaerobic endospore-formers that produce neurotoxins. Disease results when the endospores are introduced deep into the tissues. Both neurotoxins interfere with motor control.
Botulism toxin, produced by C. botulinum, binds the cytoplasmic membranes of motor neurons at the synapse and prevents the release of acetylcholine neurotransmitter and, consequently, prevents signaling to muscle cells. When muscle cells do not receive signals from motor neurons, they remain relaxed, resulting in a flaccid paralysis. Lack of motor control produces a long list of symptoms, the most serious of which is respiratory failure, because respiratory muscles can be affected by botulism toxin.
Tetanus toxin, produced by C. tetani, targets inhibitory neurons, which release neurotransmitters that prevents muscle cells from responding to acetylcholine stimulation to contract. Under normal circumstances, when one muscle of an antagonistic pair is stimulated to contract, the other muscle is inhibited from contracting, allowing for normal movement by alternate flexion and extension. When tetanus toxin blocks the release of inhibitory neurotransmitter, both muscles of the antagonistic pair contract spasmodically and sometimes lock in continuous contraction, resulting in nonflaccid paralysis. Loss of control of the respiratory muscles can lead to respiratory failure. Tetanus toxin can also interfere with autonomic (involuntary) muscle control, which may result in irregular heartbeat and possibly heart failure.