by Sarah Whyte

Eschericia coli is a family of bacteria that lives in the digestive tracts of humans and animals, a family that has about 170 members. One of them,O157:H7, produces a toxin that breaks down the human gut lining and can damage the kidneys.

All E.coli infections begin with fecal material, so any contact with feces bacteria can be a potential problem, for example, by changing diapers, drinking improperly treated water, or handling animals directly (a particular risk for farmers).

Consumption of contaminated meat is one of the more common modes of O157:H7 transmission. Controlling O157:H7 in meat begins with understanding how it gets there. All it takes is one animal to shed E.coli O157:H7 in the pen during or before slaughter. Even small amounts of the bacteria in manure matted on the hides of animals can then contact and contaminate carcasses.

Processing equipment is another concern. It can be contaminated by contact with manure or rumen contents, and, in turn, spread the bacteria to many other carcasses.

Consumers, too, have a role, in handling raw meat hygienically, keeping it cold, and cooking it adequately to eliminate risk.

Producers, processors, and inspectors all have important roles in reducing the risk of E.coli O157:H7 contamination. Their job isn’t an easy one. Bacteria can never be eliminated completely, and they can easily spread between animals. To make matters more difficult, animals carrying O157:H7 are hard to spot because they don¹t get sick.

Research is improving the ability to reduce E.coli O157:H7 contamination from farm-to-fork and a number of research goals have been identified:

• reducing the amount of E.coli O157:H7 carried by cattle;
• designing the safest possible processing procedures;
• evaluating pasteurization systems;
• evaluating environmental sources of transmission;
• developing ways to test for the presence of E.coli O157:H7; and,
• enhancing consumer understanding.

Since 1997, OCA has committed more than $250,000 to E. coli-specific research. OCA’s Research committee has also allocated a further quarter of a million dollars from the yet unreleased round three Safety Net funding to the same cause. The following projects being funded by the Ontario Cattlemen’s Association are currently addressing several of these important objectives.

Preventing E.coli O157:H7 contamination

By Sarah Whyte

The following project is budgeted to receive up to 24,000 in research funding from the Ontario Cattlemen’s Association’s Research committee

The tests that are currently available for finding harmful bacteria like E.coli O157:H7 in foods are often not very practical. The tests take time and they're often not sensitive enough to meet the needs of the food industry.

According to research by Dr. Mansel Griffiths at the University of Guelph, a step can be added to make testing both faster and more effective.

By using "biosorbents", solutions that are designed to absorb a certain kind of bacteria, researchers and technicians can separate the bacteria they want to test for from any other bacteria. With the help of special techniques, they can then count the number of bacteria in the biosorbent.

For his research, Dr. Griffiths first designed two slightly different biosorbents, each designed to absorb only E.coli O157:H7. He then tried the biosorbents out to see how well they captured the bacteria, comparing them with a different biosorbent that is already commercially available.

In order to see how effective the biosorbents were, Dr. Griffiths used two different methods for tracking E.coli O157:H7 absorption. First, he genetically altered the E.coli O157:H7 by adding genes from a "bioluminescent" bacteria -- one that naturally emits light – called Photorhabdus luminescens.

With the added genes, the E.coli O157:H7 literally glowed, making it easy to detect both the bacteria captured by the biosorbent and the bacteria left behind. Because this method only detects modified bacteria, it is useful in a laboratory, but not in a practical setting.

The second method also involved a bioluminescent agent, but this one was added later and attached to ATP, a substance present in all cells. This test is not specific for E.coli O157:H7 on its own, but with the help of a biosorbent that has sorted out the right bacteria, it can be used to measure the harmful E.coli strain both in a laboratory and in practical settings.

Both of Dr. Griffiths’ biosorbents proved to be more effective than the commercially available one at absorbing E.coli O157:H7, capturing up to 100 per cent of the target cells. None of the biosorbents captured other kinds of E.coli cells, proving that they were effective at sorting out only O157:H7.

Some fine-tuning remains before these procedures will be ready for use in the food industry. For example, the method is not as effective in high-volume samples as it is for low-volume samples. It hasn¹t yet been tried on actual samples of ground beef, nor has it been tested on samples with small concentrations of the target organism and larger concentrations of other bacteria.

When these additional research objectives are met, Dr. Griffiths’ testing methods will provide an accurate way to detect E.coli O157:H7 in less than two hours.

Detecting E.coli O157:H7 in beef processing environments

By Sarah Whyte

The following project is budgeted to receive up to $21,000 in research funding from the Ontario Cattlemen’s Association’s Research committee

Contaminated cutting equipment in meat processing facilities can spread harmful bacteria from one carcass to the next. Keeping the equipment clean, therefore, is an extremely important precaution, but not one that’s simple to achieve.

Knowing what bacteria can adhere to the equipment, how to eliminate those bacteria, and how to detect the presence of the bacteria can all contribute to better bacterial control, and, ultimately, safer food.

These were the goals of research conducted by Heidi Schraft at the University of Guelph. First, Dr. Schraft tested 18 different E.coli strains, including O157:H7, to see if they could grow on stainless steel. All of them could, and none could be removed with simple rinsing.

Next, she fed four of the strains and let them grow into a biofilm on the stainless steel. Biofilms are dense layers of bacteria and other substances, which support the continued growth of bacterial colonies. They can form in a short period of time and are often not visible to the eye.

The different biofilms were then examined under a microscope. A good understanding of how different biofilms are made up can lead to the use of an effective cleaning agents, or, if necessary, the development of new ones. Schraft is now testing the sanitizers commonly used in meat processing environments to see how effective they are at removing the biofilms produced by harmful bacteria.

The final goal of this research project was to test for E.coli biofilms in actual beef processing environments, which proved difficult because there is still no reliable way to detect E.coli bacteria without culturing it and growing it in a laboratory. When there is, inspectors will be able to test for harmful strains on-site quickly and easily.

Using vaccines to reduce fecal shedding of E.coli O157:H7

By Sarah Whyte

The following project is budgeted to receive up to $24,740 in research funding from the Ontario Cattlemen’s Association’s Research committee

On farms, newly-weaned calves have the highest rates of E.coli 0157:H7 infection. Researchers believe that these calves play a major part in spreading the bacteria within herds.

Reducing the level of E.coli O157:H7 in newly-weaned calves, therefore, would have a great impact on overall farm levels. Vaccination has been proposed as one way to achieve this goal.

A team of researchers at Health Canada and the Ontario Veterinary College at the University of Guelph has developed and tested an E.coli 0157:H7 vaccine.

So far, the vaccine does not appear successful at controlling E.coli O157:H7 infections, but the researchers are optimistic that a successful vaccine can eventually be developed.

Led by Dr. Roger Johnson, the team of researchers vaccinated six calves, three times each with inactivated samples of the bacteria, the toxin it produces, and another protein, intimin, which the bacteria uses to attach itself to the intestine wall.

These six calves and another six control calves were then infected with active E.coli 0157:H7 under strict infection confinement conditions. The researchers collected blood and feces samples to monitor how the two groups of calves responded to the bacteria. After 50 days, the calves were euthanized, and the researchers looked for O157:H7 in their colon and intestines. Some encouraging evidence was found in the calves’ blood samples after vaccination. All vaccinated calves produced high levels of antibodies to O157:H7 and to its toxin, indicating that they were mounting a defense to the bacteria.

However, after the calves were challenged with active bacteria, the control calves quickly caught up. They developed their own antibodies to the vaccine, while antibody levels in the vaccinated calves stayed about the same.

Similar amounts of E.coli O157:H7 were shed by the control and vaccinated calves. In all cases, the most bacteria were shed three days after infection, and the bacteria dropped to low levels again between days 10 and 19. It did appear that the vaccinated calves, on average, stopped shedding more quickly than the control calves.

The researchers conclude that this particular vaccine is not a viable solution to the E.coli O157:H7 problem. The immediate results are somewhat discouraging, but the researchers say that into vaccines continues and the goal of developing a safe, efficacious vaccine for this important infection can be realized. According to team leaders Dr. Johnson and Dr. Scott McEwen, "we should not give up on developing an effective vaccine. It is just not as simple as we had hoped for and the benefits to public health could be very substantial."