Some imported eggs sold in fresh markets and supermarkets have tested positive for high levels of bacteria that can cause food poisoning.

After testing 14 egg samples this month, Polytechnic University's Department of Applied Biology & Chemical Technology said it discovered that the egg shells of five samples had as much as 1.5 million bacteria each.

The five samples came from Germany, Thailand, the mainland and an unknown source.

According to Food & Environmental Hygiene Department safety standards, more than 1 million bactiera in food is unsafe.

An additional two samples from the mainland and Japan contained more than 300,000 bacteria - an alert level.

In another egg test, it was found that five samples tested positive for food-poisoning risk after they were exposed to a temperature of 30 degrees Celsius for two hours.

That exposure, as well as being kept in dirty environments, most likely caused for the high bacteria levels, according to Associate Professor Peter Yu.

He advised caution when handling eggs.

"The bacteria are invisible to human eyes," he said, adding that it can easily spread from one food to another during preparation.

To protect ourselves from possible food poisoning, he said, we should put eggs in the refrigerator and eat them within a week.

Foods, such as the uncracked eggs, should also be rinsed. And pasteurized eggs, he said, contain less bacteria.

Through September of this year, there had been 516 cases of food poisoning reported to the Health Department.

Gastroenterology and hapatology specialist Desmond Yiu said food poisoning is usually caused by bacterial infections from salmonella or listeria.

People who have low immunity, particularly children, the elderly and pregnant women, have a higher risk of infection.

Yiu said that other than avoiding raw-egg consumption, people should wash their hands before and after handling eggs, store them below 4 degrees Celsius and don't expose them to room temperature for more than two hours.

(HK Edition 11/19/2008 page1)