Taylor Farms still tied to cyclospora outbreak despite 'false positive,' FDA says

A cyclosporiasis outbreak that has likely sickened thousands of people in the U.S. is still tied to iceberg lettuce processed by a major produce supplier, the Food and Drug Administration stressed on Monday as the agency sought to clean up its communications about a 'false positive' test result that prompted widespread consumer confusion.

The FDA is still advising the public to not consume recalled products from Taylor Farms that have been identified as a likely source behind an outbreak of severe gastrointestinal illnesses across five states; the products include lettuce served in Taco Bell locations and sold at certain Walmart stores.

But the agency's attempt on Monday to reiterate that Taylor Farms products are still linked to the center of the outbreak underscored the difficulty of not only investigating the source of an elusive public health threat, but also conveying the findings of fast-moving investigations to the broader public.

'Our weekend communications around a false positive test result do not change the basis for FDA's ongoing outbreak investigation or the epidemiological data supporting the current voluntary recall by Taylor Farms,' acting FDA Commissioner Kyle Diamantas, who served as the FDA's top food regulator before being elevated to his current role, told reporters on Monday.

As part of expanded surveillance for the parasite, the FDA found a positive test on a subsequent batch of iceberg lettuce imported by Taylor Farms late last week, which was not part of the recall. The FDA said Sunday that was a false positive, but that the recall for the lettuce previously imported remained in place.

The FDA cited 'complexity in detection' of the parasite but generated confusion as to whether Taylor Farms products had been cleared of responsibility.

Taylor Farms said on Sunday that the FDA had 'apologized' to the company for the false positive test result, which prompted an FDA official to push back on Monday by saying the agency had only provided 'factual information' to the company regarding its tests and investigation. The company did not immediately respond to a request for comment.

The FDA currently has no confirmed positive sample test results, but the agency said its 'traceback investigation' identified Taylor Farms de Mexico as providing 'shredded iceberg lettuce used by Taco Bell locations where sick people ate before becoming ill.'

Donald Prater, the FDA's acting deputy commissioner for food, said officials believed the initial positive result was important public knowledge given that a positive result could implicate more Taylor Farms products in the outbreak.

'False positives are not common,' Prater told reporters on Monday. 'Test results are difficult to obtain, and most of the time, our traceback and epidemiologic information are what allows us to determine the source of the outbreak.'

Susan Mayne, the former director of the FDA's Center for Food Safety and Applied Nutrition, said the evidence shows a 'strong signal' linking the Taylor Farms lettuce to the outbreak in certain states.

'You've got epidemiology, you've got traceback,' she said. 'The third piece of information that FDA tries to get, but it's always the hardest to get, is can they find product that was implicated in the recall and test it for the pathogen.'

It is not uncommon for test results to be inconclusive, former FDA Commissioner Robert Califf told POLITICO. 'Equivocal tests are very common,' Califf said. 'So is the human instinct to value a "test result" more than a constellation of factors.'

Taylor Farms issued a recall for the lettuce 'out of an abundance of caution' and said they are continuing to work with authorities to find the culprit. 'We are committed to working with public health authorities as the ongoing outbreak investigation continues,' Taylor Farms said in a statement.

Cyclospora is a parasite that is found on fresh produce and can cause diarrhea, leading to dehydration. Dozens of patients have been hospitalized and none have died, according to the latest data from the Centers for Disease Control and Prevention.