ATLANTA (AP) -- Half the meat and poultry sold in the supermarket may be tainted with the staph germ, a new report suggests.
The new estimate is based on just 136 samples of beef, chicken, pork and turkey purchased from grocery stores in Chicago, Los Angeles, Washington, D.C., Flagstaff, Ariz. and Fort Lauderdale, Fla.
Proper cooking kills the germs, and federal health officials estimate staph accounts for less than 3 percent of foodborne illnesses, far less than more common bugs like salmonella and E. coli.
The new study found more than half the samples contained Staphylococcus aureus, a bacteria that can make people sick. Worse, half of those contaminated samples had a form of staph that's resistant to at least three kinds of antibiotics.
"This study shows that much of our meat and poultry is contaminated with multidrug-resistant staph," Paul Keim, one of the study's authors, said in a statement. "Now we need to determine what this means in terms of risk to the consumer."
Keim and his co-authors work at the nonprofit Translational Genomics Research Institute in Arizona. Their study is to be published in the journal Clinical infectious Diseases, an institute spokesman said.
Staph germs are commonly found on the skin and in the noses of up to 25 percent of healthy people. The bacteria can be spread in many settings, including in the packing plant or in the kitchen, and it can cause food poisoning.
The Centers for Disease Control and Prevention estimates that staph accounts for roughly 240,000 cases a year. Handwashing and proper cooking are the best ways to avoid problems.
The study's authors note that livestock and poultry are steadily fed low doses of antibiotics at industrial farms. They suggest that may be a contributor to the antibiotic resistance seen in some meat samples.
Among the types of drug-resistant germs the researchers found, one was methicillin-resistant staph, or MRSA, a superbug that can be fatal. They found MRSA in three of the 136 samples.
Food and Drug Administration officials say meat does not seem to be a significant route for MRSA transmission, but health officials continue to study the issue.
The government doesn't routinely check retail meat and poultry for staph bacteria. However, a fairly recent FDA pilot study in the Washington area looked at more than 1,100 meat and poultry samples and found staph in 280 of them.
A Louisiana State University study of 120 meat samples found it in almost half of pork chops and 20 percent of beef steak samples. That study, published in 2009, calculated the superbug MRSA was in about 5 percent of pork samples and 3 percent of beef.
In a statement Friday, the American Meat Institute said the study is misleading.
"Despite the claims of this small study, consumers can feel confident that meat and poultry is safe," said James H. Hodges, the organization's president.