Universitas Helsingiensis


The quarterly of the University of Helsinki
"It Must Be Something That I Ate"
The number of food poisoning cases in the EU has rocketed in the past five years. According to Mirja Salkinoja-Salonen, Professor of Microbiology, the health effects of food-borne microbial toxins are grossly underrated. These toxins may have effects other than just gastric trouble: research links them to dementia, loss of hearing, and even depression.

Henrikki Timgren

Back to winter issue 2002


According to our current knowledge, there is a total of 5,007 different species of bacteria.

For millions of years, they have led their own peculiar lives, not minding the ways of the rest of the world. Nevertheless, bacteria are extremely important to us humans: without them we would not be able to function. On the other hand, every single day, they are responsible for sending millions of people running for the bucket or even to hospital.

Risks at work and at home

Mirja Salkinoja-Salonen is head of a research team on industrial and environmental microbiology at the University of Helsinki. She says that the most salient reason for the increase of food poisonings is the increase of mass catering. Yesterday’s pasta is a real hotbed for bacteria.

“Re-heating food is the commonest cause of food poisoning. This is why food that has not been consumed needs to be refrigerated immediately. Few catering facilities, however, have such refrigerating lines,” Salkinoja-Salonen explains.

Pre-prepared foods, which are nowadays commonly used at home, constitute another serious risk. “Semi-finished foods, such as meat pies, are the worst. They are usually packed in a protective atmosphere but as soon as you open the package, the microbes begin to multiply. Within a few hours, pre-prepared food left at room temperature may become inedible. This is something many consumers cannot understand.”

Some extremely toxic bacteria do not cause any strange taste or smell at all in the food. “Quite recently, a Finnish couple contracted serious food poisoning after having eaten re-heated meat and macaroni pie. They got sick after the first time they re-heated it but didn’t think it was the food because it tasted so good. So they ate of it a second time and got an even more serious case of poisoning,” Salkinoja-Salonen recounts.

Bacteria vs. politicians

According to Professor Salkinoja-Salonen, the battle against food poisoning is hampered by the lack of education among consumers and catering personnel.

“It’s awful that teachers of home economics, nowadays, are taught almost nothing about the hazards of microbes to foodstuffs and how to avoid them. On the whole, the current atmosphere is hostile to natural sciences. Nobody wants to listen to the experts,” Salkinoja-Salonen snaps.

European politicians and authorities have participated in building this bacteria bomb. “The British Parliament agreed to pass a bill making salmonella controls mandatory only after the entire House of Commons happened to contract salmonella,” Salkinoja-Salonen says with a wry smile.

In Finland, the legal limit for listeria bacteria in milk products is practically zero, whereas in cold-smoked fish, the level allowed is hundredfold.

Cleaning the basins at fish farms all the time is said to be unreasonably expensive. So the authorities are content with just recommending that people at risk should avoid cold-smoked fish.

“The decision-makers seem to reason that the poisoning can’t be all that serious as there aren’t more people dead,” Salkinoja-Salonen ponders.

Permanent damage

Unfortunately, the microbial toxins do not stick to the politicians’ bipolar logic. “The toxins produced by the bacteria Bacillus cereus, common in foodstuffs, cause apoptosis in the border patrol of the human body, that is, the killer cells commit suicide. The killer cells having been knocked out, the body’s capability to fend off infections is diminished.”

Although the killer cells are renewed after the microbe attack, the microbial toxins remain in the body and may over the years cause permanent damage to non-renewable tissues such as nervous and cardiac cells.

“Apoptosis of the cells in the central nervous system is a major cause of dementia. Moreover, microbial toxins destroy cells in the auditory nerve. Consequently, loss of hearing with age may be caused by microbial toxins. Even depression may partly be caused by the accumulation of toxins in the nervous system,” Salkinoja-Salonen lists.

Pig sperm to EU laboratories

A while back, Salkinoja-Salonen’s research team made an internationally remarkable discovery: bacteria of the Bacillus cereus group contain the extremely dangerous toxin cereulide. Cells in the human colon are destroyed in the same way as pig spermia are when they come in contact with food containing cereulide.

“Gastric cells are just as sensitive to this toxin as the spermia are. Pig sperm, then, helps to identify whether a particular foodstuff has caused food poisoning. And it is available at insemination stations year round. Moreover, using pig sperm makes experiments on animals for the most part unnecessary.”

The new method has received wide acclaim. Among others, the Swedish Dairy Association’s research centre has already adopted it. The EU committee on feedingstuffs also requires that the sperm test be made before registration of new additives in animal feed.

“I’m sure that with time it will be commonly used in all EU countries. Last week alone, we received 60 samples for testing, even all the way from Italy. I wish that the national research institutes would learn to carry out these tests themselves. But the change will take time,” Salkinoja-Salonen muses.

top Back to winter issue 2002