Mystery of listeria food poisoning revealed
September 10, 2010
Lesley Ciarula Taylor
STAFF REPORTER
Scientists have cracked the mystery of why listeria in food makes some people deathly ill and not others.
“Food poisoning is unpredictable,” said Dr. Colin Hill of University College Cork in Ireland. “We’ve found that listeria is a clever bacteria always able to sense and adapt to its surroundings.”
In 2008, 22 Canadians died in the largest listeria outbreak in the country’s history, traced to a Toronto-area Maple Leaf Foods plant. Just six months ago, two Ontarians were hospitalized with food poisoning traced to processed deli meats.
“Pathogens are normal parts of the environment, present everywhere,” said Hill. “To completely eliminate listeria from food is very difficult.”
What Hill found, however, was that people who eat contaminated food that is also high in glutamate, such as soft cheese or meat products, have a higher chance of coming down with food poisoning than people who eat contaminated low glutamate food.
The listeria bacteria can adapt itself to withstand the acid in a person’s stomach – the first line of defence against food poisoning – if it’s exposed to an “acid shock” on the food before it’s eaten. Suddenly, it’s far more lethal.
While Hill’s research found these parameters, it doesn’t mean there are hard and fast rules to what and how to eat, he said.
“You can eat low glutamate food and wash it down with highly acid tomato juice and that could trigger the bacteria, while eating the same food without the tomato juice wouldn’t have. But the tomato juice itself won’t give you food poisoning.”
Because listeria typically attacks more vulnerable people – young children, the elderly, pregnant women – harder, future research may be able to better construct high-risk diets, he said.
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