In a study sure to spark debate among health advocates and meat producers, researchers say they have found drug-resistant strains of bacteria in meat and poultry from U.S. grocery stores at alarmingly high rates.

The study by the Translational Genomics Research Institute (TGen) found nearly half of the meat and poultry samples - 47 percent - were contaminated with S. aureus, and more than half of those bacteria - 52 percent - were resistant to at least three classes of antibiotics, according to the study published today in the journal Clinical Infectious Diseases.

But in a response to the study, University of Minnesota researchers Peter Davies and Liz Wagstrom wrote that staph aureus is a common bacterium found on the skin of people and animals, so it would have been unusual to have not found it on meat.

Although Staph should be killed with proper cooking, it may still pose a risk to consumers through improper food handling and cross-contamination in the kitchen, the Tgen researchers say.

The study

Researchers collected and analyzed 136 samples - covering 80 brands - of beef, chicken, pork and turkey from 26 retail grocery stores in five U.S. cities: Los Angeles, Chicago, Fort Lauderdale, Flagstaff and Washington, D.C.

"For the first time, we know how much of our meat and poultry is contaminated with antibiotic-resistant Staph, and it is substantial," said Lance B. Price, Ph.D., senior author of the study and Director of TGen's Center for Food Microbiology and Environmental Health. "The fact that drug-resistant S. aureus was so prevalent, and likely came from the food animals themselves, is troubling, and demands attention to how antibiotics are used in food-animal production today."

Densely-stocked industrial farms, where food animals are steadily fed low doses of antibiotics, are ideal breeding grounds for drug-resistant bacteria that move from animals to humans, the report says.

Antibiotics are the most important drugs that we have to treat Staph infections; but when Staph are resistant to three, four, five or even nine different antibiotics - like we saw in this study - that leaves physicians few options," Price said.

Industry response

The American Meat Institute (AMI) joined in the critique of the study, calling it misleading.

"Authors of the new study, which involved a small number of samples from retail stores, claim that their findings suggest that a significant public health risk exists," AMI said in a statement. "However, federal data from the Centers for Disease Control and Prevention (CDC) show steady declines in foodborne illnesses linked to consumption of meat and poultry overall and indicate that human infections with Staphylococcus aureus comprise less than one percent of total foodborne illnesses."

The study, funded by the Pew Commission, says the U.S. government routinely surveys retail meat and poultry for four types of drug-resistant bacteria, but S. aureus is not among them. The paper suggests that a more comprehensive inspection program is needed.