A growing number of medical researchers say more than 8 million women are at risk of difficult-to-treat bladder infections because superbugs - resistant to antibiotics and growing in chickens - are being transmitted to humans in the form of E. coli.

"We're finding the same or related E. coli in human infections and in retail meat sources, specifically chicken," said Amee Manges, epidemiologist at McGill University in Montreal.

If the medical researchers are right, this is compelling new evidence of a direct link between the pervasive, difficult-to-cure human disease and the antibiotic-fed chicken people buy at the grocery store.

"What this new research shows is, we may in fact know where it's coming from. It may be coming from antibiotics used in agriculture," said Maryn McKenna, reporter for the Food & Environment Reporting Network, working on a joint investigation with ABC News.

The Food and Drug Administration says 80 percent of all antibiotics sold in the United States are fed to livestock and even healthy chicken to protect them from disease in cramped quarters. It also helps the chickens grow bigger and faster.

"We're particularly interested in chickens. They, in many cases, are getting drugs from the time that they were in an egg all the way up to the time they are slaughtered," Manges said.

The chicken industry disputes the researchers' conclusions, and quoted Dr. Randall Singer, associate professor epidemiology at the University of Minnesota's Department of Veterinary and Biomedical Sciences, who said: "These studies have nothing to do with antibiotics in poultry product and further changes to antibiotic use in poultry will not change the potential human health risks associated with these foodborne E.coli."

Researchers acknowledge that there is no study showing a definitive link between the E.coli in chicken and infection in women, but point out that a study like that would be unethical because it would require intentionally exposing women to the bacteria.

They say that there is persuasive evidence that chicken carries the same bacteria with the highest levels of resistance to medicine as causes the drug resistant infection in women.

See the National Chicken Council's full statement on the ABC News report.

Adrienne LaBeouf, 29, is among the women suffering from a constant infection.

"It feels like I have some kind of infection that just won't go away," she said.

LaBeouf of Washington, D.C., has visited her doctor about her persistent bladder infection. "It was cured for a little while," she added, "and then it comes back with a vengeance."

ABC News' Brian Hartman contributed to this report.