Taylor Farms lettuce test tied to cyclospora probe was false positive
Federal officials said no product sample has been confirmed positive for cyclospora, while a recall of iceberg lettuce from central Mexico remains in place.
By Priya Raghavan · Science Reporter
3 min read
Federal food safety officials said Sunday that a lettuce sample from Taylor Farms de Mexico had been wrongly reported as positive for cyclospora. The correction matters because the company’s iceberg lettuce remains under recall during a multistate outbreak investigation, even though the FDA now says it has no confirmed positive product test.
The U.S. Food and Drug Administration said it reached that conclusion after reviewing the sample results again. The agency said that, as of July 19, no product testing had confirmed cyclospora in any sample.
The FDA said the mistaken result does not change Taylor Farms’ voluntary recall of iceberg lettuce sourced from central Mexico. The agency said it is still working with the company to make sure products tied to the outbreak are no longer being sold.
Taylor Farms said Sunday night that the FDA had made an error and apologized. The company also said the agency had not found a single product sample that tested positive for cyclospora, and said it would keep cooperating with public health officials as they investigate the outbreak’s origin.
Recall remains in effect
Taylor Farms de Mexico announced Friday that it was voluntarily recalling iceberg lettuce from central Mexico in the United States because of possible cyclospora contamination. According to the FDA, the recalled products had been sent to retailers in 27 states.
The FDA had focused on the lettuce after saying it was supplied to Taco Bell restaurants in five states where people reported eating before becoming ill. Taco Bell said Friday that it would stop using Taylor Farms de Mexico as its lettuce supplier.
In a consumer alert Friday, the FDA told people not to eat shredded iceberg lettuce from Mexico that had been served at Taco Bell locations in Indiana, Kentucky, Michigan, Ohio and West Virginia.
The FDA had posted Saturday that a sample tested positive and said at the time that the product was outside the existing Taylor Farms recall. The agency also said then that the company was trying to determine whether any of the implicated lot was still in stores or consumers’ homes. That update has since been removed from the FDA’s outbreak page.
Testing error cited
The FDA said the Saturday result was caused by false amplification and should be treated as a false positive. Amplification-based testing makes copies of genetic material so laboratories can look for organisms that may be difficult to detect by other methods, according to research published in the Annals of Clinical & Laboratory Science.
The Centers for Disease Control and Prevention has said nearly 7,000 cyclosporiasis cases have been confirmed or are under investigation in the United States since May 1. Experts say the foodborne illness can cause severe watery diarrhea, fatigue and loss of appetite.
Thomas Gremillion, director of food policy at the Consumer Federation of America, said last week that cyclospora is difficult to grow in a laboratory.
Donald W. Schaffner, chair of food science at Rutgers University, said Sunday by email that Taylor Farms was right to issue the recall regardless of the test’s status. He said false positives can occur because testing for cyclospora is difficult, and he said the FDA showed courage by correcting the record.
Schaffner said the correction could add to consumer confusion. He also said regulators should provide more information when reporting positive test results, including the rate of false positives, so the public can better understand the limits of the science.
This story draws on original reporting from NBC News.