Question
Botulism
Answer
Botulism is a severe, potentially fatal flaccid paralytic illness caused by Clostridium botulinum neurotoxin — the most potent biological toxin known.
Toxin and mechanism: C. botulinum produces botulinum toxin (multiple antigenic types, A–G, with types A, B, and E most commonly causing human disease), which is absorbed into the bloodstream and acts at the peripheral cholinergic (neuromuscular) junction, cleaving SNARE proteins required for docking/fusion of acetylcholine-containing vesicles, thereby blocking acetylcholine release — producing a descending, symmetrical flaccid paralysis, in contrast to the spastic paralysis of tetanus toxin (which blocks inhibitory neurotransmitter release centrally).
Clinical forms:
- Foodborne botulism — ingestion of pre-formed toxin in improperly canned/preserved, low-acid foods (home-canned vegetables, fermented foods) where anaerobic spore germination and toxin production occurred; presents with descending paralysis (starting with cranial nerve palsies — diplopia, dysphagia, dysarthria — then progressing to limb weakness and potentially respiratory failure), typically without fever and with a clear sensorium.
- Infant botulism — ingestion of spores (classically from honey), which germinate and produce toxin in situ in the infant gut (whose immature flora fails to suppress colonization) — presents with constipation, poor feeding, hypotonia (“floppy baby”), and weak cry.
- Wound botulism — spores contaminate a wound, germinate under anaerobic conditions, and produce toxin locally, notably associated with injection drug use.
Laboratory diagnosis: demonstration of toxin in serum/stool/food by mouse bioassay (classical reference method) or newer immunoassays/PCR; culture of the organism from stool/wound is supportive but not always necessary for diagnosis, which is often made clinically given the urgency of treatment.
Treatment: trivalent/heptavalent botulinum antitoxin (neutralizes circulating, unbound toxin — must be given early, since it cannot reverse paralysis already established), supportive care including ventilatory support for respiratory failure, and, for infant botulism, human botulism immunoglobulin.