Compare and contrast the pathogenicity of Clostridium botulinum and Clostridium tetani, including mechanisms of action of their toxins and disease manifestations
What will be an ideal response?
Both bacteria are anaerobic endospores-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, which result in a flaccid paralysis. A long list of symptoms is produced by the lack of motor control, the most serious of which is respiratory failure, since respiratory muscles can be affected by botulism toxin.
Tetanus toxin, produced by C. tetani, targets inhibitory neurons, which release inhibitory neurotransmitter 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 non-flaccid paralysis. Loss of control of the respiratory muscles can lead to respiratory failure. Tetanus toxin can also interfere with autonomic (non-voluntary) muscle control, which may result in irregular heartbeat and possibly heart failure.
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