Taylor Farms remains under FDA review in lettuce-linked outbreak
The FDA said a false positive cyclospora test does not change its investigation into a cyclosporiasis outbreak tied to recalled lettuce.
By Tom Brennan · Health & Medicine Correspondent
3 min read
The Food and Drug Administration said Monday that Taylor Farms remains part of its investigation into a cyclosporiasis outbreak, even after the agency determined that one lettuce sample had falsely tested positive for the parasite. The clarification matters because Taylor Farms’ voluntary recall of shredded iceberg lettuce distributed to 27 states remains in effect.
The FDA said late Sunday that a lettuce sample from Taylor Farms had produced a false positive for cyclospora, the parasite that causes cyclosporiasis. The agency said that sample was not from lettuce already tied to the outbreak or recall, but from a different shipment collected during routine import checks.
In a post Monday on X, the FDA said the false positive did not alter the basis for its outbreak investigation or the epidemiological evidence supporting Taylor Farms’ recall. The agency said its inquiry into the outbreak continues.
Taylor Farms said Sunday that the FDA had “apologized” over the false positive test result. NBC News reported that an FDA official disputed on a Monday call that the agency had issued an official apology.
How investigators are tracing the outbreak
Foodborne outbreak investigations usually do not rest on a single laboratory result, according to Donald Schaffner, a food microbiology professor and chair of the food science department at Rutgers University. Schaffner said investigators review patient samples, interviews with people who became ill, receipts and supply-chain records to identify the likely source of contaminated food.
In this outbreak, investigators found that many sick people had eaten at Taco Bell restaurants supplied with Taylor Farms lettuce, according to the report. The Centers for Disease Control and Prevention said that, as of Saturday, it had confirmed more than 1,600 cases in Indiana, Kentucky, Michigan, Ohio and West Virginia.
Schaffner said Taylor Farms remains implicated because of the epidemiology: people who ate at Taco Bell and consumed Taylor Farms lettuce became sick with the parasite. He said that link is statistical and does not by itself prove causation, but he said the evidence was strong enough for the FDA and CDC to treat the lettuce as the likely source.
Taco Bell said Saturday that it had removed all Taylor Farms lettuce from its U.S. restaurants.
False positive does not end food warning
Schaffner said it is unusual for investigators to detect cyclospora in a food sample because the product is often gone, spoiled or already eaten by the time an investigation advances. A confirmed positive food sample can add strong support to an outbreak finding, but investigators often have to rely on other evidence.
Don Stoeckel, an environmental microbiologist and associate at the Produce Safety Alliance, said a true positive result for cyclospora would have provided strong confirmatory data. He said the absence of such a result does not reduce the need to follow the CDC’s recommendation to avoid the product named in its investigation.
Cyclosporiasis is caused by the cyclospora parasite. Public health agencies continue to focus on the recalled shredded iceberg lettuce while the FDA reviews evidence from patients, restaurants and the supply chain.
This story draws on original reporting from NBC News.