Infant botulism was first described in 1976. It is caused by Clostridium botulinum, a gram-positive anaerobic bacillus found most commonly in soil and agricultural products. The organism forms spores and during growth and germination releases a potent neurotoxin that is responsible for the illness. Eight neurotoxins have been recognized, but infant botulism is caused primarily by organisms producing toxin types A and B.
Although adult-type botulism occurs by ingesting food contaminated with botulinus toxin, infant botulism seems to result from ingestion of spores that germinate and release the toxin inside the infant's colon. The toxin is absorbed from the gastrointestinal tract, travels via the blood stream, and binds irreversibly to peripheral cholinergic nerve synapses, where it prevents the release of acetylcholine.