Which is the most potent bacterial exotoxin known?

Which is the most potent bacterial exotoxin known?

• A. Botulinum toxin
• B. Erythrogenic toxin
• C. C. difficile toxin B
• D. C. perfringens alpha-toxin

Answer: (A)

Potency of a bacterial exotoxin is about how little is needed to cause deadly effects and how the toxin disrupts a critical system. Botulinum toxin is the most potent known bacterial exotoxin. It operates at extraordinarily low doses, enough to cause fatal paralysis, because it blocks the release of acetylcholine at neuromuscular junctions. Mechanistically, it’s a protease that cleaves SNARE proteins necessary for vesicle fusion, so acetylcholine cannot be released to stimulate muscle contraction. The result is flaccid paralysis and potential respiratory failure, which is why even tiny amounts can be lethal. The other toxins listed are harmful, but they do not reach this extreme level of potency. Erythrogenic toxin drives the rash and illness seen in scarlet fever, C. difficile toxin B promotes colitis by damaging intestinal cells, and C. perfringens alpha-toxin damages cell membranes via phospholipase activity. They cause serious disease, but their lethality per dose is far lower than that of botulinum toxin.

Potency of a bacterial exotoxin is about how little is needed to cause deadly effects and how the toxin disrupts a critical system. Botulinum toxin is the most potent known bacterial exotoxin. It operates at extraordinarily low doses, enough to cause fatal paralysis, because it blocks the release of acetylcholine at neuromuscular junctions. Mechanistically, it’s a protease that cleaves SNARE proteins necessary for vesicle fusion, so acetylcholine cannot be released to stimulate muscle contraction. The result is flaccid paralysis and potential respiratory failure, which is why even tiny amounts can be lethal.

The other toxins listed are harmful, but they do not reach this extreme level of potency. Erythrogenic toxin drives the rash and illness seen in scarlet fever, C. difficile toxin B promotes colitis by damaging intestinal cells, and C. perfringens alpha-toxin damages cell membranes via phospholipase activity. They cause serious disease, but their lethality per dose is far lower than that of botulinum toxin.