Taco meat tainted with C. perfringens bacteria sickened staff members at an Iowa high school.

DES MOINES – Cooked ground beef tainted with Clostridium perfringens (C. perfringens) bacteria sickened 50 staff members at Roosevelt High School in October, the Polk County Health Department said in a report detailing its investigation into the matter.

The cooked meat was in tacos served to teachers and staff members who attended a catered luncheon on Oct. 21. Des Moines Public Schools said about half the faculty members became sick, and classes were dismissed early. Testing by the State Hygienic Laboratory uncovered C. perfringens bacteria in the meat. The bacteria also were found in several of the affected individuals’ stool samples.

Cooking can kill growing C. perfringens cells that cause food poisoning, the health department said, but not necessarily the spores that can grow into new cells. The spores can grow into new cells if cooked food is not promptly served or refrigerated. Symptoms of C. perfringens infection usually end within 24 hours, while less severe symptoms may last up to two weeks. No long-term health consequences are associated with the infection, the health department noted.

In a statement, Des Moines Public Schools said it plans to use the incident as an opportunity to remind schools and consumers about the importance of following food safety guidelines.

“We are relieved this is an isolated incidence of foodborne illness, that our teachers reported only short-term illnesses, and that no students were involved,” the district said. “The health department did not identify a specific point in time between the catered food preparation and the school’s food handling as being responsible for the presence of a bacteria.”

The cooked meat was purchased at a Hy-Vee grocery store. In a statement, Hy-Vee spokeswoman Tara Deering-Hansen said the meat was not catered by the retailer, but cooked meat was picked up at a store by school staff.

“Roosevelt High School officials picked up cooked taco meat from our Windsor Heights store the morning of Wednesday, Oct. 21,” Deering-Hansen said. “Our internal review indicates that the taco meat was prepared and stored properly while at our store.

“As you know, we can’t control how food is handled after it leaves our stores,” she added. “We can confirm there had been no other reported illnesses from products purchased at the Windsor Heights Hy-Vee, and none of the employees who handled the taco meat had been recently ill. Our staff will continue to fully cooperate with Polk County Health Department officials as they carry out their investigation.”

C. perfringens is one of the most common causes of foodborne illness in the United States, according to the Atlanta-based Centers for Disease Control and Prevention (CDC). The CDC estimates that the bacteria cause nearly one million cases of foodborne illness annually. Beef, poultry, gravies and dried or pre-cooked foods are common sources of infection.