Serum levels of equine-botulism antitoxin to toxin types A, B, and E were measured in four type-A botulism patients who had received equine-botulism antitoxin. High circulating levels capable of neutralizing in excess of 1 X 10(8), 9 X 10(7), and 6 X 10(6) 50% mouse lethal doses of toxin of types A, B, and E, respectively, were detected. There was little depletion of type-A antitoxin even though two of the patients had circulating type-A toxin before treatment. The half-life for antitoxin persistence for one patient was calculated as being 6.5, 7.6, and 5.3 days for antitoxin types A, B, and E, respectively. Antitoxin levels were not proportionate to the amount (range, 2-4 vials) injected and did not appear to be affected by whether the route of administration was iv or im. Peak serum levels of antitoxin were 10-1,000 times higher than amounts needed to neutralize the toxin measured in the serum of these and other patients with botulism.

In the period November 13-18, 1978, seven cases of type A botulism occurred in persons who had eaten in a restaurant in Colorado. The outbreak was recognized when two persons who had independently eaten at the restaurant were hospitalized with an illness compatible with botulism. Surveillance efforts identified five additional cases. Potato salad made at the restaurant and available for service during an 11-day period was epidemiologically incriminated as the vehicle of botulinal toxin transmission (p less than 0.00001). Laboratory studies showed that Clostridium botulinum spores on the surface of potatoes could survive baking in the manner used by the restaurant and that botulinal toxin could be produced in potatoes contaminated with C. botulinum spores.