No E. coli was detected in samples of beef patties used in McDonald's Quarter Pounders that have been linked to a deadly outbreak, a company spokesperson said Sunday, citing tests by the Colorado Agriculture Department.
The department has no further plans to test the beef patties, the company spokesperson said, and the patties have been ruled out as the source of the outbreak.
The most likely source of contamination was slivered onions from a single source, the company spokesperson said, citing the Food and Drug Administration.
McDonald’s stopped sourcing slivered onions from that source — Taylor Farms Colorado Springs — indefinitely on Sunday, the company spokesperson said, days after it removed the Taylor Farms onions from its supply chain.
The onions from Taylor Farms were sold in stores in Colorado, Kansas, Wyoming and parts of other states in the area, the spokesperson said. Some of those locations included airports, which could account for cases in other states.
The McDonald's spokesperson said the company is confident asking beef suppliers to provide a fresh supply of patties for distribution. Quarter Pounders are expected to be available in restaurants this week.
All 900 restaurants that get onions from Taylor Farms Colorado Springs will continue selling Quarter Pounders without onions for the time being, the company spokesperson said.
No other burgers or McDonald's menu items were affected by the outbreak.
The strain of E. coli in the outbreak, called O157:H7, produces a powerful toxin that can damage the lining of the small intestine.
The outbreak was first reported Tuesday, when the Centers for Disease Control and Prevention announced it was investigating an E. coli outbreak linked to McDonald's Quarter Pounders in multiple states, prompting the fast-food chain to stop using slivered onions and quarter-pound beef patties in several states, the agency said at the time.
The CDC said Tuesday that the first E. coli case linked to McDonald's occurred Sept. 27. State health officials in Colorado notified the CDC of an unusual uptick in the illness on Oct. 10, and the agency started investigating Oct. 15, Matt Wise, chief of the CDC's Outbreak Response and Prevention Branch, told NBC News.
The CDC zeroed its investigation in on the slivered onions on the Quarter Pounders by Wednesday. On Thursday, McDonald's said the onions linked to the outbreak came from Taylor Farms.
On Wednesday, distributor U.S. Foods said Taylor Farms was recalling four raw onion products out of an abundance of caution because of "potential E. coli contamination." The company urged its customers, including restaurants, to stop using and to destroy affected products as soon as possible.
It also prompted other restaurant chains in Colorado — including Illegal Pete's and Taco Bell — to stop using onions on their menus.
A spokesperson for Yum! Brands, Taco Bell's parent company, said selected Pizza Hut and KFC locations have also removed fresh onions from their menus. There are no signs of E. coli illnesses linked to those restaurants.
The FDA said Thursday it was looking into Taylor Farms as the possible source of the E. coli outbreak linked to the Quarter Pounders but added that "we're looking at all possible sources."
A spokesperson for Taylor Farms did not immediately respond to a request for comment Sunday.
As of Friday, 75 people across 13 states had been infected with the E. coli strain and one person had died, according to the CDC.
Twenty-two people have been hospitalized, and two people have developed hemolytic uremic syndrome, a severe complication that can cause permanent kidney failure or death.
Multiple people have sued McDonald's claiming they became sick after they ate at the restaurant.
