Featured Research

from universities, journals, and other organizations

University Of Nebraska Research Reveals Surprises About E. Coli 0157:H7

November 25, 1999
University Of Nebraska, Lincoln
A new genetic "fingerprinting" method developed by University of Nebraska food scientists is revealing surprising insights about potentially deadly E. coli 0157:H7 bacteria.

LINCOLN, Neb. -- A new genetic "fingerprinting" method developed by University of Nebraska food scientists is revealing surprising insights about potentially deadly E. coli 0157:H7 bacteria.

Related Articles

The new technique shows that there are two genetically distinct E. coli 0157:H7 populations found in cattle -- one that causes sometimes fatal food poisoning in people and a second that is not commonly isolated from food poisoning cases. Previously, relationships of different E. coli 0157:H7 populations weren't well-understood.

Genetic results suggest that the population most commonly found in cattle either is non-virulent, meaning it is incapable of causing disease, or it is not easily transmitted to people, said Food Microbiologist Andy Benson, whose laboratory developed the technique that led to the findings.

"Our method gives a very high-resolution snapshot of the genome and lets us see things we couldn't see before," Benson said. The technique, called octamer-based genome scanning (OBGS), allows researchers to pinpoint where genetic differences exist on E. coli's DNA and offers a means for rapidly cloning and identifying the genes at those DNA sites.

Because the OBGS technique will be broadly applicable to many organisms, this Institute of Agriculture and Natural Resources research is generating great interest among genetics researchers. A paper detailing the work of Benson and food science department colleagues Jaehyoung Kim and Joseph Nietfeldt was published this month in the Proceedings of the National Academy of Sciences.

Benson was struck by the idea for the genome scanning method while attending a research conference. After spending eight months working out the bugs, Benson tested the technique on E. coli samples, called isolates, drawn from humans and cattle. All the isolates originated in a three-county region of Wisconsin. Researchers expected that the isolates, when illustrated on an evolutionary tree-type structure called a dendrogram, would be dispersed throughout the structure.

"We really weren't prepared for what we saw," Benson said. Most of the human isolates were clustered together in one part of the dendrogram, and most of the cattle isolates were clustered together, indicating that there were significant genetic differences between the two groups.

"That could mean two things," Benson said. Either their data were biased because all were collected from the same region, or -- surprisingly -- the E. coli population infecting cattle in Wisconsin was distinct from the population making people sick.

To test for bias, Benson's team used the method again on a large group of isolates gathered from 16 states. Again, two distinct populations -- human and bovine -- appeared on the dendrograms.

Benson's hypothesis: the cattle population either is very inefficient at causing human illness or it is a weak population that does not survive the necessary hurdles to infect people and cause E. coli related illness.

This could be good news for the public health and for cattle producers, especially following data recently released by U.S. Department of Agriculture researchers at the Meat Animal Research Center (MARC) at Clay Center, Neb., that found E. coli 0157:H7 to be present in more than half of cattle tested.

"This fits well with the MARC data," Benson said. "Only about 20,000 cases of human infection with E. coli 0157:H7 are reported each year. You would expect a much higher number, given the number of cattle infected." In comparison, an estimated 2 million cases of Salmonella poisoning occur annually, many caused by eating contaminated poultry and beef, Benson said.

"The key for us now is to get a good fix on the numbers," Benson said. "Our numbers now suggest that two-thirds of the isolates from cattle are genetically related to the apparently non-virulent population -- the population that doesn't cause illness. But we need to do a much larger sample size to get a better idea of exactly what that number is. We're doing that now."

Benson's team analyzed 78 E. coli 0157:H7 samples to reach the current results. He plans to test hundreds to get his "good fix on the numbers."

As with all significant research, Benson's work has opened many new avenues of study.

"We have our work cut out for us. There are a lot of different directions we can go with this," he said.

The researchers already are fine-tuning the OBGS method, making it faster and easier. Another ongoing project is cloning and sequencing the DNA of a specialized virus, called a bacteriophage, that Benson believes is associated with the genetic divergence between the E. coli populations. Sequencing work on the bacteriophage may provide clues to the mystery of why the prevalent bovine 0157:H7 population isn't commonly found in humans.

Perhaps the most practical application of the OBGS method will be in developing a more sensitive test of E. coli 0157:H7 isolates, Benson said.

"We're using OBGS to pinpoint what the exact genetic differences are between populations so that we can develop a much simpler test that can discriminate the two. This would make it much easier to do extensive testing, such as in feedlot populations," he said.

Benson cautions that researchers must be careful not to over-interpret the data at this point. The newly-discovered population must be tested to determine if it is, in fact, non-virulent. The most powerful experiment is one that can't be done, Benson said.

"The only way to be absolutely sure the non-virulent 0157:H7 population won't cause human illness would be to test it on people. Obviously, this isn't an experiment that we could do or would do, so we have to come at it from other ways, such as using model systems, epidemiology studies and in vitro studies," Benson said.

This IANR Agricultural Research Division research was funded by a USDA National Research Initiative competitive grant and by Nebraska Legislative Bill 1206, which appropriated $250,000 annually for five years for E. coli research.

Story Source:

The above story is based on materials provided by University Of Nebraska, Lincoln. Note: Materials may be edited for content and length.

Cite This Page:

University Of Nebraska, Lincoln. "University Of Nebraska Research Reveals Surprises About E. Coli 0157:H7." ScienceDaily. ScienceDaily, 25 November 1999. <www.sciencedaily.com/releases/1999/11/991125090704.htm>.
University Of Nebraska, Lincoln. (1999, November 25). University Of Nebraska Research Reveals Surprises About E. Coli 0157:H7. ScienceDaily. Retrieved October 25, 2014 from www.sciencedaily.com/releases/1999/11/991125090704.htm
University Of Nebraska, Lincoln. "University Of Nebraska Research Reveals Surprises About E. Coli 0157:H7." ScienceDaily. www.sciencedaily.com/releases/1999/11/991125090704.htm (accessed October 25, 2014).

Share This

More Plants & Animals News

Saturday, October 25, 2014

Featured Research

from universities, journals, and other organizations

Featured Videos

from AP, Reuters, AFP, and other news services

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Deep Sea 'mushroom' Could Be Early Branch on Tree of Life

Reuters - Innovations Video Online (Oct. 24, 2014) Miniature deep sea animals discovered off the Australian coast almost three decades ago are puzzling scientists, who say the organisms have proved impossible to categorise. Academics at the Natural History of Denmark have appealed to the world scientific community for help, saying that further information on Dendrogramma enigmatica and Dendrogramma discoides could answer key evolutionary questions. Jim Drury has more. Video provided by Reuters
Powered by NewsLook.com
Black Bear Cub Goes Sunday Shopping

Black Bear Cub Goes Sunday Shopping

Reuters - Light News Video Online (Oct. 23, 2014) Price check on honey? Bear cub startles Oregon drugstore shoppers. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Dances With Wolves in China's Wild West

Dances With Wolves in China's Wild West

AFP (Oct. 23, 2014) One man is on a mission to boost the population of wolves in China's violence-wracked far west. The animal - symbol of the Uighur minority there - is under threat with a massive human resettlement program in the region. Duration: 00:41 Video provided by AFP
Powered by NewsLook.com
Breakfast Debate: To Eat Or Not To Eat?

Breakfast Debate: To Eat Or Not To Eat?

Newsy (Oct. 23, 2014) Conflicting studies published in the same week re-ignited the debate over whether we should be eating breakfast. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.


Breaking News:

Strange & Offbeat Stories

Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News


Free Subscriptions

Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile

Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?

Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins