Antibiotics in Poultry May Pose Risk to Humans

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(HealthDay News) -- Could a turkey sandwich or a bowl of chicken soup be hazardous to your health?

Poultry has that potential, according to research that suggests people who eat drug-treated poultry may be at increased risk of developing antibiotic resistance.

Still, the findings are preliminary and shouldn't make anyone stop eating chicken or turkey, the study's lead investigator said.

"We don't want to suggest to anyone that they should alter their diet based on this," said Dr. Edward Belongia, director of the Marshfield Clinic Research Foundation's Epidemiology Research Center in Wisconsin.

But federal regulators should consider the results as they make rules about the kinds of drugs given to poultry, the investigator added.

At issue is the use of virginiamycin, an antibiotic used in farm animals to boost their growth.

The drug is banned in Europe, but farmers are allowed to use it in the United States.

Some studies have suggested that virginiamycin can cause germs in poultry to become super-powered, much as overuse of antibiotics in humans has made some people immune to certain drugs.

This phenomenon, known as drug resistance, happens when an antibiotic is used so often that germs mutate around it.

It's possible for drug resistance to be spread through food. "When we consume food with organisms that have resistance genes, these genes can be transferred to our natural organisms, causing them to become drug-resistant," explained Molly Marten, a clinical epidemiologist at Scripps Mercy Hospital in San Diego who's familiar with the study findings.

Belongia and colleagues launched their study to see if people who ate chicken or turkey treated with antibiotics would themselves become resistant to an antibiotic known as quinupristin-dalfopristin, or Synercid.

Synercid treats disease caused by Enterococcus faecium, germs that are normally found in the gut and can cause disease in some cases.

The illnesses caused by these germs are especially common in hospitals among patients whose immune systems are weakened.

The study authors looked for signs of drug resistance by looking at enterococcus bacteria found in stool samples from 105 newly hospitalized patients and 65 healthy vegetarians, all living in the Midwest.

They also looked for signs of drug-resistance in enterococcus bacteria found in 77 samples of ordinary poultry from retail stores and 23 samples of poultry raised without antibiotics.

The findings of the study, which was funded by the federal government, are published in the Nov. 1 issue of the Journal of Infectious Diseases.

The researchers said they did not find any sign that the humans had developed resistance to Synercid from eating poultry. However, they said that "plenty" of drug-resistant enterococcus was found in poultry treated with antibiotics, Belongia said.

Furthermore, 38 percent of the hospitalized patients had a genetic trait that might make it easier for them to develop resistance to Synercid; none of the vegetarians had the trait.

Patients who ate the most chicken seemed most susceptible to developing immunity to the drug, as did those who touched poultry.

Right now, this isn't a major problem because Synercid isn't used a great deal, Belongia said. That means germs haven't had a chance to become immune to it.

"But that could change," he said.

Belongia believes that the U.S. Food and Drug Administration should take the findings into account. In a written statement, Belongia said that antibiotics should not be used to promote growth in animals.

"This research makes a strong case for limiting the use of antibiotics in food-producing animals," added Marten, the epidemiologist. "By using antibiotics for strictly therapeutic purposes (such as treating an infection), rather than as a growth promoter, we will slow the emergence of drug-resistant organisms in human populations."

More information:

Learn more about drug resistance from the World Health Organization.