Research Suggests Strategy to Prevent Deadly E coli in Cattle

Wednesday, May 12 2010

Written by Bill Loftus

MOSCOW – Scientists, including the University of Idaho's Carolyn Hovde Bohach, Monday reported they have learned how deadly E. coli bacteria sense the cattle gastrointestinal tract.

The work may provide "an exciting alternative to diminish contamination of meat products and cross-contamination of produce crops because of cattle shedding this human pathogen," the scientists reported in this week's issue of the Proceedings of the National Academy of Sciences.

The research focused on E coli O157:H7, a serotype of enterohemorrhagic Escherichia coli, which can cause fatal illness when transmitted to people through produce or undercooked meat.

An estimated 70 to 80 percent of healthy cattle herds in the United States at least sometimes carry the deadly E. coli with no ill effects, passing it to each other through their environment or by direct contact with each other.

E. coli from the farm environment, presumably in feed or water, is ingested by cattle and passes through the rumen, the first and largest compartment in their four-part stomach along the GI tract until it reaches the rectoanal junction mucosa where it attaches and colonizes.

To be successful, E. coli must express or turn on different genes in different conditions such as outside of the animal, in the rumen, or at the end of the GI tract. This publication shows, for the first time, how E. coli O157:H7 uses chemical signaling to sense its environment and turn on different genes when it is in cattle, Hovde Bohach said.

Through a process known as quorum sensing, the bacterium senses and responds to chemicals known as AHLs or acyl-homserine lactones. The presence of AHL activates genes that help E coli colonize cattles' GI tract.

Disrupting that signal may prevent the deadly E. coli from taking up residence in cattle. Human health researchers are studying whether disrupting quorum sensing in another bacterium, Pseudomonas aeruginosa, can prevent fatal infections in cystic fibrosis patients.

The main threat for people occurs from cattle shedding the bacteria in feces, which can then contaminate meat or produce.

The cattle work was conducted on the University of Idaho campus, where Hovde Bohach's laboratory has developed expertise in working with the bacteria in its natural silent reservoir, cattle.

There may be several strategies to stop E. coli from living in cattle, she said, adding, "We might try to limit production of AHLs or find a feed additive that would block bacterial reception of the AHL signal."

Her research includes a focus on the influence of cattle diet on shedding the bacteria and where the bacteria are found within cattle.

Vanessa Sperandio and David T. Hughes of the University of Texas Southwestern Medical Center reported the team's findings in the Proceedings of the Academy of Sciences. Other authors included Linda Liou of Hovde Bohach's lab at the University of Idaho, Jason W. Sahl and David A. Rasko of the University of Maryland School of Medicine, Arati V. Patankar and Juan E. Gonzalez of the University of Texas at Dallas; Thomas S. Edrington of the USDA Agricultural Research Service.

An abstract of the team's report is available on the Proceedings of the National Academy of Sciences website.

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About the University of Idaho
Founded in 1889, the University of Idaho is the state’s flagship higher-education institution and its principal graduate education and research university, bringing insight and innovation to the state, the nation and the world. University researchers attract nearly $100 million in research grants and contracts each year; the University of Idaho is the only institution in the state to earn the prestigious Carnegie Foundation ranking for high research activity. The university’s student population includes first-generation college students and ethnically diverse scholars. Offering more than 130 degree options in 10 colleges, the university combines the strengths of a large university with the intimacy of small learning communities. The university is home to the Vandals, the 2009 Roady’s Humanitarian Bowl champions. For information, visit

About the University of Idaho
The University of Idaho helps students to succeed and become leaders. Its land-grant mission furthers innovative scholarly and creative research to grow Idaho's economy and serve a statewide community. From its main campus in Moscow, Idaho, to 70 research and academic locations statewide, U-Idaho emphasizes real-world application as part of its student experience. U-Idaho combines the strength of a large university with the intimacy of small learning communities. It is home to the Vandals. For information, visit