Clostridium perfringens outbreak associated with minestrone soup.

Clostridium perfringens food poisoning usually occurs after animal protein foods such as meat or poultry are consumed. In November 1990, an outbreak of gastrointestinal illness occurred among attendees at a conference of cake decorators held in Michigan. All 42 conference attendees were surveyed. Thirty-two of 42 (76%) attendees reported gastrointestinal symptoms. The median incubation period was 6.5 hours (range, 1.5-15 hours). Ill persons were almost five times more likely to have consumed minestrone soup than were those who were not ill (relative risk = 4.92, 95% confidence interval 1.23-infinity). Bacteriologic analysis identified C. perfringens in the soup and in 11 of 12 stool specimens from ill persons. The soup was cooked 2 days prior to serving and was slowly cooled before refrigeration; it was briefly reheated on the day served. Failure to monitor time and temperature controls during the cooling and reheating of the soup probably allowed for C. perfringens proliferation in the minestrone soup. This investigation demonstrated that nonanimal protein sources, such as legumes, can support substantial C. perfringens growth and should be regarded as potential vehicles in C. perfringens outbreaks.