Sask. student’s vaccine tightens net against E. coli

Food and water around the world could soon become safer for human consumption thanks to a new cattle vaccine created by University of Saskatchewan graduate student David Asper.

The veterinary microbiology student’s work, soon to be published, is premised on the idea that humans can be protected from harmful bacteria by vaccinating cattle that are the source of the bacteria.

Asper’s work builds on groundbreaking research by his supervisor Andrew Potter, director of the Vaccine and Infectious Disease Organization (VIDO) International Vaccine Centre.

Potter’s work led to the first cattle vaccine against E. coli O157, the leading cause of “hamburger disease.” The vaccine prevents the bacteria from attaching to the animal’s intestines and from colonizing, cutting the disease off at the source.

“The E.coli O157 vaccine is the first of its kind worldwide and is expected to significantly lessen the amount of E. coli O157 present in food products and also in the environment,” said Potter.

But while E. coli O157 is the most prevalent type of E. coli in North America, it’s just one of hundreds of E. coli bacteria around the world that cause disease by producing shiga toxin.

These shiga toxin-producing E. coli (STEC) produce infections that can range from very mild to severe or even life-threatening.

“Right now, STEC bacteria is the number one cause of renal (kidney) failure in children around the world,” said Asper. “It affects adults too, but children are the most susceptible.”

STEC bacteria cause disease in humans if meat becomes contaminated during slaughter or if feces mix with groundwater, polluting drinking or swimming water or food supplies. But the STEC bacteria that cause human illness generally do not make animals sick so healthy cattle often have STEC bacteria living in their intestines.


What Asper has been able to do is create a vaccine prototype to protect cattle against a number of non-O157 STEC bacteria that are responsible for human outbreaks of disease around the world.

“David has broadened the scope of the work we’ve done, and I think the impact is large,” said Potter. “He essentially created this vaccine on his own.”

With funding from the Canadian Institutes of Health Research, the Natural Sciences and Engineering Research Council (NSERC) and Bioniche, the commercial developer of Potter’s vaccine, Asper has created the second-generation vaccine prototype and participated in initial testing on mice and cattle.

The vaccine will now be put through extensive testing that could take three to five years.

Though E. coli O157 is the most prevalent STEC bacteria in North America, others are more dominant around the world. In Europe, O26 is the most common and in South America, it is O111.

“One place where this could make a huge difference is Argentina,” said Asper. “They have 10 times the cases of renal failure that we do in Canada. This vaccine could reduce sickness and deaths caused by E. coli by a large amount.”

Due to improved detection methods, cases of non-O157 E. coli infection are on the rise, increasing the importance of having the second-generation vaccine.

“We can protect humans by vaccinating animals before they come in contact with the pathogen. I think that’s very important work that will lead to a lot fewer infections,” Asper said.

His work could help prevent tragedies such as the 2000 incident in Walkerton, Ont. when fecal material from cattle seeped into the water system, contaminating drinking water and resulting in thousands of illnesses and seven deaths in the community.

Just as the E. coli O157 cattle vaccine will be a significant tool for use by beef and dairy producers to mitigate human infection risk, Asper’s vaccine could also lessen financial losses to meat producers. When STEC bacteria is found in just one meat sample, beef processors are required to destroy the entire shipment — a significant cost to farmers.

Asper recently defended his Ph.D. and is to begin a industrial post-doctoral fellowship in the fall.

— Anne-Marie Hickey is a student intern in the University of Saskatchewan’s research communications office. Article appears with permission of U of S.


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