A patient presents with ascending flaccid paralysis after consuming home-canned vegetables. Electromyography shows decremental response at low-frequency stimulation. The toxin acts by:
- A Blocking glycine receptors at inhibitory interneurons in the spinal cord
- B Activating adenylate cyclase via ADP-ribosylation of Gs protein
- C Cleaving SNAP-25 and/or synaptobrevin (VAMP), preventing acetylcholine vesicle fusion ✓
- D Disrupting tight junctions of intestinal epithelium via zonula occludens toxin
Correct answer: C. Cleaving SNAP-25 and/or synaptobrevin (VAMP), preventing acetylcholine vesicle fusion
Explanation
Clostridium botulinum toxins (types A, B, E, F) are metalloproteinases that cleave SNARE proteins (SNAP-25, synaptobrevin/VAMP, syntaxin), preventing fusion of acetylcholine vesicles with the presynaptic membrane at the neuromuscular junction, causing flaccid paralysis. Tetanus toxin blocks glycine and GABA release at inhibitory interneurons causing spastic paralysis. Cholera toxin ADP-ribosylates Gs. Zonula occludens toxin is produced by Vibrio cholerae.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.