PCR identified as a method to combat food-borne pathogens

If you’ve ever gotten sick from eating lettuce, you can probably blame Cyclospora cayetanensis. First reported as a pathogen in the 1980s and described in the early 1990s, no one in the US really talked much about it until it was fingered as the culprit in a number of high-profile food-borne infection cases.

How you get sick from eating salad

As explained in a detailed analysis of a pathogen outbreak stemming from a doomed holiday lunch in Germany in 2000, human waste likely winds up in the fertilizer used to grow suspect vegetables, or water contaminated with fecal matter was used to irrigate crops, prepare pesticides, or fresh and clean produce. In other worse, poo got in the food. (See? I told you it was not pretty.)

Using rtPCR for food poisoning prevention

But after years of looking at the salad bar with a skeptical eye, science is showing up to the buffet line with a solution: real-time polymerase chain reaction (rtPCR).

PCR is method for amplifying a segment of DNA. A method for molecular detection of Cyclospora cayetanensis was first developed in 2004 but its use was problematic. More recently, scientists at the US Food and Drug Administration have developed and validated a better method for recovery and ID of C. cayetanensis using PCR in which the produce was washed, DNA were extracted from the wash, and PCR amplification was used to find the "bad" stuff.

“The new method has been validated for cilantro and raspberries in a multi-laboratory validation study and for shredded carrots, parsley, basil, romaine lettuce in matrix extension studies,” FDA notes.

The new method, FDA adds, offers increased sensitivity, specificity, and throughput, and it delivers results much faster.

For now, health experts still advise you to wash any fruits and vegetables that you can’t peel—and to be especially cautious when eating fruits and vegetables when traveling. The exception? Pre-cut, bagged, or packaged produce items which are labeled as pre-washed and ready to eat. Washing them can actually introduce germs.

"It is unlikely that consumer washing of such products will make the product cleaner compared to a commercial triple wash," Michelle Annette Smith, a food safety expert with the US Food and Drug Administration, wrote in a post about the issue. "It is possible that the additional handling may contaminate a product that was clean."