A new study by Consumer Reports has found that two out of three whole broiler chickens are contaminated with illness-inducing bacteria, while certain types of organic chicken posed the lowest risk.

The researchers studied 382 whole broilers bought from more than 100 stores in 22 states and found salmonella or campylobacter bacteria on two-thirds of the birds tested. The research suggests that current safety and hygiene practices among poultry producers and handlers are inadequate and that consumers need to be vigilant at both the grocery store and at home to cook chicken well and prevent cross-contamination of countertops, hands and other foods.

Both types of bacteria are among the leading causes of food-borne illness in the United States, infecting at least 3.4 million Americans annually and sending 25,500 to hospitals. Every year about 550 people die from food-borne salmonella infections, and about 100 die after contracting campylobacter from food, according to estimates from the Centers for Disease Control and Prevention. Although a few products, including Perdue-brand broilers and organic air-chilled chickens, were the safest, the magazine called chicken suppliers “a very dirty industry that needs better practices and tighter government oversight.”

Over all, campylobacter was detected in 62 percent of the chickens, while salmonella was in 14 percent. Nine percent of the birds contained both pathogens. Based on the study, a consumer has a one in three chance of buying a broiler free of both pathogens.

The cleanest birds were organic “air-chilled” broilers – 60 percent of these broilers were free of both pathogens. Typically, chickens are dunked in cold chlorinated water. In the air-chilling process, the carcasses are refrigerated and may be misted, rather than dunked, according to the magazine.