Botulism from Home-Fermented Tofu

The spores of Clostridium botulinum — ubiquitous in the environment — can germinate and produce toxin under anaerobic conditions; food-borne botulism is caused by eating foods contaminated with this toxin. Cases are rare in the U.S. and are usually associated with consumption of home-canned goods and traditional fermented Alaska Native foods.

In March 2012, two patients — recent immigrants from China — presented at the same hospital in Queens, New York, with histories of vomiting, followed by dysphagia and dysarthria. Both showed cranial nerve deficits, ptosis, oculomotor palsy, dilated pupils, and diminished tendon reflexes. In patient 1, an edrophonium chloride test was indicative of myasthenia gravis, but electromyography was suggestive of botulism, and a test for antibodies to acetylcholine receptors (diagnostic of myasthenia) was negative. Stool samples were positive for botulinum toxin type B by mouse bioassay, as was the tofu sample from the patient's home. The patient responded to administration of botulinum antitoxin and was discharged to a rehabilitation facility. His wife had ingested the same fermented tofu but remained healthy. Patient 2, who was hospitalized 25 days after patient 1, did not have botulinum toxin detected but also recovered after antitoxin administration.

The two patients had purchased bulk tofu from the same market and had followed the fermentation procedures common in the Chinese province from where they had emigrated. Bulk tofu from the market, although stored under suboptimal conditions, was free of botulinum toxin, as was the sample from patient 2's home.