Taylor Farms continues to be under investigation by the Food and Drug Administration over the growing cyclosporiasis outbreak, despite a false-positive test result, the agency announced Monday.
Late Sunday, the FDA said a sample of lettuce from the company had falsely tested positive for cyclosporathe parasite responsible for the disease. This sample, however, did not come from lettuce already implicated in the outbreak and recall. Instead, it came from a separate shipment that the agency collected during routine import inspections.
“To clarify, this false positive laboratory sample does NOT change the basis of the FDA’s ongoing outbreak investigation or the overwhelming epidemiological data supporting the current voluntary recall by Taylor Farms,” the statement said. The FDA said Monday.
The company’s voluntary recall of shredded iceberg lettuce in 27 states remains in effect.
On Sunday, Taylor Farms said in a statement that the FDA had “apologized” for the false positive test results. In a call Monday, an FDA official disputed Taylor Farms’ claim that the agency had issued a formal apology.
Taylor Farms did not immediately respond to requests for comment.
Determining the source of an outbreak goes beyond finding a positive sample.
Public health officials don’t rely solely on laboratory tests to identify the source of a foodborne outbreak, said Donald Schaffner, professor of food microbiology and chair of the food sciences department at Rutgers University.
Instead, investigators look at patient samples and interviews, food receipts and information from the food supply chain to determine where the contaminated food likely came from.
During the ongoing outbreak, investigators found that many people who became ill had eaten at Taco Bell restaurants stocked with Taylor Farms lettuce. From Saturday, the Centers for Disease Control and Prevention had confirmed more than 1,600 cases in people in Indiana, Kentucky, Michigan, Ohio and West Virginia.
“Taylor Farms is still involved due to the epidemiology,” Schaffner wrote in an email. “This means that people who ate at Taco Bell and ate Taylor Farm lettuce are sick with the parasite. It’s important to realize that this is just a statistical correlation. Correlation is not causation, but it was strong enough evidence for the FDA and CDC to believe it is the cause.”
On Saturday, Taco Bell announced that it had removed all Taylor Farms lettuce from its U.S. restaurants.
Schaffner said it was unusual that investigators were able to detect the cyclospora parasite in a food sample.
“It’s almost always too late because the food is already spoiled or has been eaten,” he said.
A positive result for the parasite would have been strong confirmatory data, said Don Stoeckel, an environmental microbiologist and associate with the Produce Safety Alliance, a food safety training group.
The lack of a positive result, however, “does not diminish the importance of following the CDC’s recommendation to avoid consumption of the product mentioned on the CDC investigations page,” Stoeckel said.
