Raley's Country Potato Salad
Potato salad was one item among 71 products Taylor Farms recalled due to concerns of E. coli O157:H7 contamination.

WASHINGTON – A blend of celery and onions produced by a California grower was likely not the source of a multi-state outbreak of E. coli O157:H7 infections linked to rotisserie chicken salad made by Costco, the US Food and Drug Administration reported.

The agency said its laboratory analysis did not confirm the presence of E. coli in a sample of a celery-onion mix produced by Taylor Farms Pacific Inc. in Tracy, Calif. The Montana Department of Health reported that the mix had preliminarily tested positive for the pathogen.

In November, the Atlanta-based Centers for Disease Control and Prevention along with the US Dept. of Agriculture and several states launched an investigation an outbreak of E. coli O157:H7 that sickened 19 individuals in seven states. CDC reported five individuals had been hospitalized and two case patients had developed hemolytic uremic syndrome, a type of kidney failure. Ill people were identified in California, Colorado, Missouri, Montana, Utah, Virginia and Washington.

Taylor Farms recalled 71 products on Nov. 26 when five preliminary analysis tests run by the Montana Public Health Laboratory all indicated the presence of E. coli O157:H7 in a sample of a celery and onion mix made by Taylor Farms and taken from a Montana Costco, FDA said.

“The preliminary test that was done on the sample was a polymerase chain reaction (PCR) test, which is commonly used to rapidly screen for the presence of the DNA of a bacteria, in this case E. coli O157:H7,” FDA explained. “A PCR positive result indicates that the sample may have contained DNA of the bacteria in question.”

FDA went on to say that PCR positives may not always be confirmed. For example, other bacteria that may be present in the sample can interfere with the growth and isolation of the suspect bacteria or the bacteria in question may be in very low numbers and hard to isolate or perhaps have died off by the time confirmation testing was done.

“The state of Montana provided the FDA with a partial sample of the celery/onion mix to assist with the analysis,” the agency said. “FDA’s analysis did not confirm the presence of E. coli O157:H7 bacteria in the sample.”

The investigation is ongoing, and FDA is working with federal and state agencies to conduct a traceback investigation to determine the source of the illness.