An 18-year-old woman has eaten homemade preserves. Eighteen hours later, she develops diplopia, dysarthria, and dysphagia. Which of the following is the most likely causative organism?

The incubation period of C. botulinum toxin is 18-36 hours but ranges from a few hours to days. There are no sensory symptoms. Foodborne botulinum is associated primarily with home-canned food. Severe foodborne botulinum can produce diplopia, dysarthria, and dysphagia; weakness then can progress rapidly to involve the neck, arms, thorax, and legs. There is usually no fever. Nausea, vomiting, and abdominal pain can precede the paralysis or come afterward.