Chicken bought at major supermarkets across Canada is frequently contaminated with superbugs — bacteria that many antibiotics cannot kill — an investigation by CBC TV's Marketplace has found.

Marketplace researchers — along with their colleagues at Radio-Canada's food show L'Epicerie — bought 100 samples of chicken from major grocery chains in Vancouver, Toronto and Montreal.

The chicken included some of the most familiar label names in the poultry business.

The 100 samples were sent to a lab for analysis. Two-thirds of the chicken samples had bacteria. That in itself is not unusual — E. coli, salmonella and campylobacter are often present in raw chicken.

What was surprising was that all of the bacteria uncovered during the Marketplace sampling were resistant to at least one antibiotic. Some of the bacteria found were resistant to six, seven or even eight different types of antibiotics.

"This is the most worrisome study I've seen of its kind," said Rick Smith, the head of Environmental Defence, a consumer advocacy group.

Resistance grows

The sampling results revealed that common illness-causing bacteria had turned into superbugs that are increasingly resistant to the usual treatment protocols.

How did these bacteria become superbugs? Doctors and scientists told Marketplace co-host Erica Johnson that chicken farmers are overusing antibiotics — routinely giving healthy flocks doses of amoxicillin, tetracycline, erythromycin and ceftiofur to prevent disease and to make the chickens grow bigger, faster.

A representative of the Chicken Farmers of Canada group denied that antibiotics are being overused. "I think there's judicious use that is going on," said Mike Dungate.

But it isn't clear what the industry means by "judicious use." The industry won't say how much antibiotic use is occurring, saying it doesn't keep track. The federal government doesn't track antibiotic use by farmers, and, unlike in Europe, there are no limits on the use of antibiotics in the feed and water given to chickens.

While thorough cooking kills bacteria — including superbugs — most contamination happens before the chicken is cooked through improper handling. If there's contamination by superbugs, the worry is that consumers could ingest illness-causing bugs that are then resistant to much of the available spectrum of traditional antibiotic therapy.

For Canadians who think they're safe by purchasing organic chicken or buying chicken raised without the use of antibiotics, Marketplace turned up results in its sampling that might surprise those consumers, too.