ARS researchers develop E coli prevention strategies for cattle

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Researchers at the Department of Agriculture's Agricultural Research Service are taking their fight against a deadly strain of Escherichia coli to where the bacteria lurk inside cows.

So far, the researchers have discovered that E coli O157:H7 infections can occur in calves' gallbladders, in addition to the animals' intestines. This finding could help public health veterinarians and others working with slaughterhouses to identify cattle that are infected with E coli O157:H7 and prevent meat contamination, said Evelyn Dean-Nystrom, an ARS microbiologist, who along with Dr. William Stoffregen, a veterinary medical officer at the ARS, conducted the research.

"Historically, gallbladders have been cultured for Salmonella," Nystrom said. "It might be another place to look (for E coli O157:H7)."

The finding also suggests that bile contamination may be one way E coli are spread at slaughterhouses, Nystrom said.

"We're still trying to figure out how the E coli get into the meat," she said.

Nystrom said she and her fellow researchers are currently working with slaughterhouses to determine whether the gallbladder infections they found in calves under experimental conditions also occur in animals at slaughterhouses.

While research continues on the path E coli take from cattle to humans, Nystrom is collaborating with researchers from the Uniformed Services University of the Health Sciences to develop ways to prevent E coli O157:H7 from infecting cattle, which do not become ill from the infections, and thus prevent the E coli from contaminating human food or the environment.

One strategy the researchers are exploring is using a feed-based vaccine that would cause the cattle to produce an antibody to intimin, a protein that allows the bacteria to latch onto the surfaces of the intestines, said Alison O'Brien, PhD, a microbiologist from the university who is overseeing the vaccine development.

"We're trying to produce something simple that would reduce the load of E coli O151:H7 in cattle, and reduce the amount of the bacteria that is shed into the environment and our meat—something that would not harm the cattle," O'Brien said.

The researchers have engineered tobacco plant cells to produce the vaccine and have found that the vaccine works in mice. They are currently testing whether the vaccine will work in cattle. They have contracted with Kan Wang, PhD, an Iowa State researcher who works with transgenic plants, to develop corn plants that would produce the vaccine. They are also working with Hugh S. Mason, PhD, an Arizona State researcher who develops vaccine-producing plants, to use other plants to produce the vaccine.