The safety of our food and water is a serious concern for Canadians. We need to know that the food we eat and the water we drink to stay healthy won't accidentally make us ill.

Each year, more than five million people around the world die from diseases caused by unsafe drinking water and over two million deaths result from water-related diarrhea. 

That's why researchers at the National Research Council have been working to keep E. coli, a dangerous food- and water-borne bacterium, from entering our food or water supply.

A common contaminant

Escherichia coli is a naturally-occurring bacterium that lives in the intestines of cows. Although it causes no problems for cattle, the E. coli O157:H7 strain of the bacterium produces a toxin that is dangerous to humans. If ingested, E. coli causes cramping, diarrhea and in rare cases, kidney failure or even death.

When cows carrying the bacteria are slaughtered, E. coli can sometimes get into the food supply. People who eat undercooked ground beef are at risk of becoming ill from E. coli contamination. Since contaminated meat looks and smells normal, it is important that all ground beef be thoroughly cooked to destroy E. coli bacteria. Unpasteurized milk can also become contaminated if a cow's udder or the milking equipment has traces of bacteria.

Water contamination can be caused by run-off from nearby fields that have been treated with manure containing E. coli bacterium. This is believed to be the cause of a tragic case of tainted water in Walkerton, Ontario in 2000.  

E. coli research began 20 years ago when scientists realized people were getting sick from the E. coli O157:H7 strain present in undercooked hamburger meat. They discovered the source of the bacteria was inside the cows themselves. In the mid-1980s, NRC scientists identified a unique antigenic marker in the bacterium which identifies the pathogenic strain of E. coli, making it possible to detect the bacterium. This discovery proved handy years later as scientists worked to get rid of the bacteria altogether.

Building on their discovery of the antigenic marker that identifies E. coli, NRC researchers discovered that there were other, non-pathogenic bacteria (bacteria that don't cause disease) that carried markers identical or chemically similar to E. coli O157:H7. When mice were immunized with some of these non-pathogenic bacteria, the bacteria produced antibodies that prevented the mice from becoming infected with E. coli.

While exploring the idea of using this discovery to create a vaccine against E. coli, scientists realized they would face resistance from farmers who are wary about mass-immunizations of their cattle. So researchers started working on a feed-based delivery system.

The idea was to express an E. coli O157:H7 – specific antibody in plants and then incorporate the plant-based antibody into the cows' food. Once inside a cow's digestive system, the antibody attaches to any E. coli bacterium it encounters, preventing it from attaching to the lining of the cow's stomach and multiplying.

Because it would be administered through food instead of vaccination, this new method of eliminating E. coli from cows was more readily accepted by farmers and the public.

Detecting contamination to avoid disasters

Despite these promising efforts to eliminate E. coli, more work must be done before an effective product becomes available. In the meantime the bacteria continue to thrive and have the potential to contaminate our food and water. During the tragic events in Walkerton, a whole town drank dirty water for days before being warned of the danger. By that time, the damage had already been done. Through examples like this, it's easy to see why quick detection of water contamination is essential for public safety. 

The traditional culture method of water testing involves filtering bacteria from water samples, cultivating them in petri dishes, then counting the bacteria. Although this method can detect E. coli, it is prone to errors and does not detect some other potentially lethal water-borne pathogens. What's more, the process takes two days to complete, which is far too slow when it comes to saving people from drinking deadly water.

NRC scientists have been working on using DNA chips, also called "biochips" or DNA microarrays, to quickly detect water-borne pathogens, including E. coli, with almost no error. The process involves coating a chip with the DNA of a known pathogen, then applying DNA from a water sample to the same chip. If the DNA from the sample bonds to the original DNA on the chip, it means the water sample contains the same pathogen that was originally on the chip. 

Eventually, these chips will include the DNA for many different pathogens, allowing detection at very low levels in the water. The method is fast and affordable, important factors for improving water testing and safety.

For two decades, NRC scientists have been working to eliminate E. coli and detect dangerous contaminants before they reach humans. This research is essential for ensuring the safety of our food and water in the 21^st century.