Taylor Farms remains the subject of a Food and Drug Administration investigation into a growing cyclosporiasis outbreak despite false-positive test results, the agency announced Monday.
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Late Sunday, the FDA announced that lettuce samples from the company falsely tested positive for Cyclospora, the parasite that causes the disease. However, the samples were not taken from lettuce, which has already been implicated in the outbreak and recall. Instead, it came from another shipment that authorities collected during a routine import inspection.
“To be clear, this false-positive test sample does not change the basis of FDA’s ongoing outbreak investigation or the overwhelming epidemiological data supporting the current voluntary recall by Taylor Farms,” the FDA said Monday on X.
The company’s voluntary recall of shredded iceberg lettuce in 27 states continues.
Taylor Farms said in a statement Sunday that the FDA “apologized” for the false-positive test result. In a phone call Monday, FDA officials disputed Taylor Farms’ claim that the agency had issued a public apology.
Taylor Farms did not immediately respond to a request for comment.
Determining the cause of an outbreak is about more than just finding positive samples.
Donald Schaffner, professor of food microbiology and chair of the food science department at Rutgers University, said public health officials don’t rely solely on laboratory tests to determine the source of foodborne illness.
Instead, investigators look at patient samples and interviews, food receipts, and information from the food supply chain to determine where contaminated food came from.
In the ongoing outbreak, investigators found that many of those who became ill had eaten at Taco Bell restaurants that served Taylor Farms lettuce. As of Saturday, the Centers for Disease Control and Prevention had confirmed more than 1,600 cases in Indiana, Kentucky, Michigan, Ohio and West Virginia.
“Taylor Farms remains involved in epidemiology,” Schaffner wrote in an email. “This means that people who ate at Taco Bell and ate Taylor Farms lettuce had this parasite. It’s important to realize that this is just a statistical correlation. Correlation is not causation, but the evidence was strong enough for the FDA and CDC to think this was the cause.”
Taco Bell announced Saturday that it has removed all Taylor Farms lettuce from its U.S. restaurants.
Schaffner said it is unusual for researchers to be able to detect Cyclospora parasites in food samples.
“In most cases, it’s too late because the food has already spoiled or been eaten,” he says.
A positive result for the parasite would have provided strong confirmatory data, said Don Steckel, an environmental microbiologist and associate at the Produce Safety Alliance, a food safety training group.
But the lack of a positive result “does not diminish the importance of following CDC recommendations to avoid consuming the products listed on CDC’s research page,” Stockel said.
