DALLAS May 11, 2010 Microbiologists at UT Southwestern Medical Center, working with the Department of Agriculture, have identified a potential target in cattle that could be exploited to help prevent outbreaks of food-borne illnesses caused by a nasty strain of Escherichia coli.
In the study, available online and in an upcoming issue of the Proceedings of the National Academy of Sciences, researchers interfered with a genetic sensing mechanism that allows the E. coli strain known as enterohemorrhagic O157:H7, or EHEC, to form colonies within cattle, causing the bacteria to die off before they could reach the animals' recto-anal junction, the primary site of colonization. Most other strains of E coli gather in the colon.
"We're diminishing colonization by not letting EHEC go where it needs to go efficiently," said Dr. Vanessa Sperandio, associate professor of microbiology and biochemistry at UT Southwestern and senior author of the study. "If we can find a way to prevent these bacteria from ever colonizing in cattle, it's possible that we can have a real impact on human disease.
"This could be something as simple as including some sort of antagonist in cattle feed, which would result in less shedding of the bacteria in fecal matter with less contamination down the road in food products."
Dr. Sperandio said the finding is important because an estimated 70 percent to 80 percent of the cattle herds in the U.S. carry EHEC.
Although EHEC can be a deadly pathogen to humans, the bacterium is part of cattle's normal gastrointestinal flora. EHEC harbors a gene called sdiA, which makes the SdiA protein. The SdiA protein senses a chemical made by microbes in the animal's rumen, the first of a cow's four stomachs, which serves as a large fermentation chamber. Detecting this signal allows EHEC to pass through the rumen and colonize the recto-anal junction.
For the study, the researchers injected
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UT Southwestern Medical Center