Retail pork products in the U.S. have a higher prevalence of methicillin-resistant Staphylococcus aureus bacteria (MRSA) than previously identified, according to new research by the University of Iowa College of Public Health and the Institute for Agriculture and Trade Policy.

MRSA can occur in the environment and in raw meat products, and is estimated to cause around 185,000 cases of food poisoning each year. The bacteria can also cause serious, life-threatening infections of the bloodstream, skin, lungs and other organs. MRSA is resistant to a number of antibiotics.

The study, published Jan. 19 in the online science journal PLoS ONE, represents the largest sampling of raw meat products for MRSA contamination to date in the U.S. The researchers collected 395 raw pork samples from 36 stores in Iowa, Minnesota and New Jersey. Of these samples, 26 -- or about 7 percent -- carried MRSA.

"This study shows that the meat we buy in our grocery stores has a higher prevalence of staph than we originally thought," says lead study author Tara Smith, Ph.D., interim director of the UI Center for Emerging and Infectious Diseases and assistant professor of epidemiology. "With this knowledge, we can start to recommend safer ways to handle raw meat products to make it safer for the consumer."

The study also found no significant difference in MRSA contamination between conventional pork products and those raised without antibiotics or antibiotic growth promotants.

"We were surprised to see no significant difference in antibiotic-free and conventionally produced pork," Smith says. "Though it's possible that this finding has more to do with the handling of the raw meat at the plant than the way the animals were raised, it's certainly worth exploring further."