FDA back to square one on source of cyclosporiasis outbreak after Taylor Farms false positive

The investigation into the source of the cyclosporiasis outbreak is going back to the drawing board after the Food and Drug Administration said a sample of Taylor Farms shredded lettuce produced a false positive result.

Taylor Farms, a California-based produce farm and supplier, announced a voluntary 27-state recall of its shredded iceberg lettuce on Friday after officials linked the product to the outbreak. The FDA had come out with a positive cyclospora result for Taylor Farms' iceberg lettuce on Saturday, but declared it a false positive the following day.

'Due to the complexity in detection of Cyclospora, FDA laboratory experts re-reviewed the sample results and have concluded that the finding does not represent true amplification and should be considered a false positive,' the FDA said in an update statement on Sunday evening.

The agency said it informed Taylor Farms of the false positive but that it 'continues working with the firm to ensure product implicated in this outbreak has been removed from the market.'

FDA acting Deputy Commissioner for Food Donald Prater said the false positive was found through the agency's import sampling program, which is designed to screen products rapidly for contamination before they cross the border. He explained that such a result is not a common occurrence, but can happen due to the complexity of Cyclospora.

'False positives are not common,' Prater said. 'In fact, it's very difficult to detect this parasite in food. Unlike bacteria, this parasite cannot be cultured using conventional laboratory techniques. It's extremely [hard] to detect even in food, with the highly sensitive methods that we use.'

The official said Taylor Farms is still the main suspect in the investigation into the cause of the parasite outbreak because the FDA's traceback information and epidemiological data heavily 'converge' on a single supplier, specifically shredded iceberg lettuce from Taylor Farms' location in Central Mexico.

After deeming the result a false positive, as of Sunday, the agency has not identified any confirmed positive sample results for products that could be linked to the outbreak of the parasite illness, which can cause severe diarrhea.

'Today, FDA apologized to us. Yesterday, FDA informed Taylor Fresh Foods that one of its iceberg lettuce products from central Mexico tested positive for cyclospora. Today, we were informed that FDA made a mistake, and this was a false positive,' Taylor Farms said in a statement on Sunday.

The company said the recall of its shredded iceberg lettuce sourced from central Mexico was made 'based on initial information provided by health officials, in an abundance of caution.' The recall of that product is still in place, though all of its other products remain available for purchase.

There have been 1,645 cases of cyclosporiasis confirmed to the Centers for Disease Control and Prevention since May, with over 5,100 cases undergoing further analysis nationwide. Thirty-four states have reported cases to the CDC, with the largest number in Michigan.

Cyclosporiasis is a nonfatal gastrointestinal illness that can cause severe diarrhea, loss of appetite, weight loss, cramping, nausea, and fatigue. While cases of the infection typically rise during the summer months, this year's reported cases are over six times last year's year-to-date total.