Research Looks at How E. coli Attaches to Cattle Guts
Research out of the U.S. Department of Agriculture (USDA) has discovered key gene and chemical interactions that allow Escherichia coli (E. coli) O157:H7 bacteria to colonize the gut of cattle, a problem because cattle manure contaminated with E. coli can contaminated thousands of pounds of ground beef or a crop of leafy greens (cross contamination).
The researchers, including USDA Agricultural Research Service (ARS) animal scientist Thomas S. Edrington, reported how the E. coli sense a key chemical that plays a critical role in allowing the bacteria to colonize inside the cattle’s gastrointestinal (GI) tract.
To proliferate, E. coli express genes differently based on their environment, such as outside the cattle host, inside the cattle rumen, or even at the end of the cattle GI tract. Having a better understanding of when, why and how these bacteria colonize could lead to practical applications in the future, according to Edrington.
The researchers showed that “quorum sensing” chemicals called acyl-homoserine lactones (AHLs), which are produced by other bacteria, are present within the bovine rumen but absent in other areas of the cattle GI tract. AHLs are important because E. coli harbor a regulator, called SdiA, which senses these AHLs and then prompts the E. coli to attach and colonize.
The research suggests that limiting production of the SdiA chemical, or blocking bacterial reception of the AHLs, may eventually lead to new strategies for keeping E. coli from attaching inside the animal.
The study, published in the Proceedings of the National Academy of Sciences, was conducted at the University of Idaho, Moscow, Idaho, campus. It involved researchers from several universities and was headed by Vanessa Sperandio, who is with the University of Texas Southwestern Medical Center, in Dallas.
Ohio State Researchers Connect E. coli to Swimmers
New research released by The Ohio State University reported that there is a direct link with high E.coli levels and swimmers becoming ill. 
The report also states that testing for E.coli can take up to 18 hours and that swimming advisories are usually posted a day late.
Mary Clifton with the Ohio Department of Health told NBC4-TV in Columbus, Ohio, that there is a push to get more rapid testing. The problem is that there is not an improved standard test yet to do rapid testing. The Ohio State research report said that better methods need to be in place to protect lakes from being contaminated in the first place. Shiga toxin-producing E. coli bacteria grow in the guts of cattle and other animals. The animals shed the pathogen in their feces and it can be washed into waterways during rains.
CDC E. coli Outbreak Surveillance Report for 2007
E. coli 0157:H7 and other foodborne agents cause an estimated 76 million illnesses annually in the United States.
The Centers for Disease Control and Prevention has published its latest set of data on foodborne disease outbreaks submitted from all states and territories. The CDC Surveillance for Foodborne Diseases Outbreaks Report summarizes epidemiologic data for the 1,097 reported outbreaks occurring during 2007 (the most recent finalized data), which resulted in 21,244 cases of foodborne illness and 18 deaths.
Among the 497 foodborne outbreaks with a laboratory-confirmed single etiologic agent reported, 40 were shiga toxin-producing E. coli outbreaks, primarily E. coli O157:H7. Coupled with two more suspected E. coli outbreaks, the E. coli classification accounted for 6 percent of 2007 outbreaks.
The 2007 surveillance number was much higher than the mean established from 2002-2006. In that period, the mean number of shiga toxin-producing E. coli outbreaks was 28 per year, or 2 percent of the total outbreaks.
In terms of illnesses, the 2007 report also was higher. In 2007, CDC and state health departments tracked 603 confirmed and suspected shiga-toxin E. coli illnesses. That was up from the 2002-2006 mean number of 375 E. coli illnesses per year.
It is important to note when reviewing the foodborne disease surveillance report that the actual numbers of outbreaks and illnesses in the U.S. is much higher than those confirmed by public health scientists and laboratories.
E. coli Prevention Research Focuses on Scottish Farmers
Certain farmers in the Grampain region in the north of Scotland are, to some degree, immune to the deadly bacteria Escherichia coli O157:H7, the University of Minnesota’s Center for Infectious Disease Research and Policy (CIDRAP) reports. Researchers at Bangor University in Wales tested about 200 Scottish farmers from Grampain and North Wales and it was found that about one-fifth of the farmers, or roughly 20 percent, are at least partially immune to E. coli O157:H7. The report was published August 8 on Scotsman.com.
Researcher Dr. Prysor Williams said: “We are taking small samples of blood and saliva and looking for antibodies in the samples. That will tell us if that individual has been exposed to 0157. If antibodies are present it shows that that individual has a degree of immunity because all the volunteers are not patients.”
The story reports that the study’s findings could help in the search for an E. coli vaccine, and that repeated exposure over a long period of time may be protecting these farmers from the otherwise harmful pathogen. The Scotsman story reports that the Grampain region is said to have one of the highest E. coli infection rates in the world, and results of the study suggest a much higher rate of antibodies among that region’s population. According to the story:
Rates of E coli 0157 in Scotland are higher than the rest of the UK. Last year, there were 4.6 cases per 100,000 people in Scotland, compared with fewer than two per 100,000 in England. In Grampian there were 11.1 cases per 100,000…The reasons for the higher rates in Scotland remain unclear.
Fecal Shedding Underestimates E. coli 0157:H7 Volume in Cattle
New research published this week shows that testing for E. coli O157:H7 in cow feces underestimates the prevalance of the pathogen in the animals’ gastrointestinal tract.
The research, published August 1 by the journal Applied and Environmental Microbiology, was conducted by the USDA’s Agricultural Research Service.
E. coli 0157:H7 is a dangerous foodborne pathogen in humans that grows benignly in cattle.
It is common to test cattle feces to determine if any individual animal is shedding the bacteria, but scientists are seeking more information about where in the cattle gastrintestinal tract the E. coli can be found. The information is needed for the purpose of fighting the bug.
The research team found E. coli O157:H7 in samples from the mouth, pharynx, tonsils, lymph nodes, esophagus, all four sections of the stomach, and the small and large intestines, though the specific locations of positive cultures varied between animals.
“Although 31 percent of the animals were culture positive for E. coli O157:H7 somewhere along the intestinal tract, only 26 percent of those were fecal-culture positive. These data suggest that fecal shedding underestimated E. coli O157:H7 prevalence in the beef cattle gut and identified potential intervention sites,” the researchers concluded.
In short, fecal shedding underestimated E. coli O157:H7.
E. coli in Flour and Cookie Dough Addressed at Food Protection Conference
At this year’s annual meeting of the International Association for Food Protection (IAFP) in Anaheim, California, several presentations address the issue of E. coli contamination in refrigerated cookie dough and the flour used to make it.
One presentation, “Flour Food Safety: The Changing Landscape — Escherichia coli O157:H7,” was given by representatives from Cargill, Nestle and ConAgra and outlined how the industry is reexamining flour as a potential source for E. coli contamination in food. The importance of this issue is highlighted by last year’s E. coli outbreak associated with Nestle Tollhouse raw cookie dough that sickened roughly 75 people in multiple states. According to and IAFP summary of the presentation:
“Flour has been viewed as a raw agricultural product for years; but with a recent outbreak involving consumption of an uncooked product containing flour, regulators and industry are re-examining whether flour should be treated as a RTE ingredient in some foods that may be consumed uncooked by the consumer. This mini-symposium will examine the history of flour and what industry knows about the microbiology of this product during production, harvesting and milling; the regulatory perceptions of flour as a potential vehicle of pathogens; the transformation of microbiological criteria associated with flour and the verification testing required to gauge compliance with the new criteria; and one solution available to deliver RTE flour as an ingredient.”
Another piece of research included at the conference comes from researchers at the Silliker, Inc., Food Science Center in South Holland, Illinois, and focuses on validating testing methodologies for raw cookie dough and its ingredients.
