An Outbreak of Type a Botulism Associated with a Commercial Cheese Sauce

Background: Although botulism is rare, recognition of a possible case of this illness represents a public health emergency. To prevent more cases, prompt investigation must be done to determine whether illness is linked to a commercial product or restaurant. Botulism can masquerade as other illnesses, and seemingly unlikely foods can harbor botulinum toxin. Objective: To confirm the diagnosis and determine the cause and extent of an outbreak of botulism associated with food served at a delicatessen. Design: Retrospective cohort study of patrons of the delicatessen; laboratory analysis of food, serum samples, and stool samples; and traceback of implicated food. Setting: Community in Georgia. Participants: Patrons of the delicatessen. Main Outcome Measures: Botulinum toxin in food, serum, or stool and Clostridium botulinum in food and stools. Results: 8 of 52 patrons (15%) met the case definition for botulism. In 4 of the 8 patrons, an illness other than botulism was initially diagnosed. Five of the 8 were hospitalized, and 1 died. Stool cultures from 4 patrons yielded type A C. botulinum, and two serum samples contained botulinum toxin. All ill persons ate food from the delicatessen on 1 October 1993. Of the 22 persons who ate at the delicatessen that day, all 8 ill persons but none of the 14 well persons ate a potato stuffed with meat and cheese sauce. An open can of cheese sauce contained type A botulinum toxin and yielded C. botulinum on culture. Cheese sauce experimentally inoculated with C. botulinum spores became toxic after 8 days at a temperature of 22°C (room temperature). Conclusions: A commercial, canned cheese caused a botulism outbreak. This product readily becomes toxic when contaminated by C. botulinum spores and left at room temperature. Mild botulism caused by unusual vehicles may be misdiagnosed. Botulism should be included in the differential diagnosis of persons with signs or symptoms of acute cranial nerve dysfunction.