(NaturalNews) Two out of every three store-bought chickens may be contaminated with bacteria that commonly cause human illness, according to a study conducted by the Consumers Union."Consumers still need to be very careful in handling chicken, which is routinely contaminated with disease-causing bacteria," said Urvashi Rangan, the union's director of technical policy.Researchers conducted tests on 382 fresh broiler chickens purchased at 100 retailers in 22 states in spring 2009. A full two-thirds of the chickens were contaminated with either one or both of the bacteria strains most often responsible for food-borne illness. Although this figure is an improvement over the 2007 figure of 80 percent, the Consumers Union still called the numbers "far too high" and called for stricter government regulation.Sixty-two percent of chickens tested positive for campylobacter, the number two cause of food-borne illness. Fourteen percent tested positive for salmonella, the number one cause, and 9 percent tested positive for both.In contrast, the U.S. Department of Agriculture found only 5 percent of chickens contaminated with salmonella in its tests of chicken packing plants in April, May and June 2009. The Consumers Union noted that its own tests were conducted farther down the supply chain, when more opportunities for contamination had arisen. It also pointed to prior studies finding widespread campylobacter contamination at chicken processing plants, and called upon the government to set a maximum safe threshold for levels of the bacteria.Although cooking destroys both salmonella and campylobacter contamination, people can be exposed to the pathogens while cooking or otherwise processing the raw meat. In addition, contamination can spread from uncooked chicken to other foods more commonly eaten raw. For this reason, health experts recommend that chicken always be bagged separately from other foods and refrigerated or frozen within two hours of purchase. The Centers for Disease Control and Prevention recommend keeping a separate cutting board exclusively for use on uncooked poultry, in order to prevent contamination of other foods.Sources for this story include: abcnews.go.com.