(CNN) -- Meat and poultry produced in the United States is widely contaminated with "multi-drug-resistant" bacteria, according to a study published Friday in a medical journal.
The report, published in the April 15 edition of Clinical Infectious Diseases, found that nearly half of the samples of poultry and meat used in the study were contaminated with bacteria. Slightly more than half of the contaminated samples, one out of four in all, were resistant to various antibiotics, according to the study.
"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, the study's senior author. Price also heads the Translational Genomics Research Institute's Center for Food Microbiology and Environmental Health.
The study found drug-resistant strains of Staphylococcus aureus in 47% of the samples. Of the contaminated samples, the study determined that 52% were resistant to at least three types of antibiotics. The research involved 136 samples out of 80 brands of beef, turkey pork and chicken.
The samples were collected from 26 grocery stores in Chicago; Fort Lauderdale, Florida; Los Angeles; Washington, D.C.; and Flagstaff, Arizona.
A spokesman for the U.S. Department of Agriculture said in a statement Friday that the office's Food Safety and Inspection service "monitors emerging threats and we, along with our federal partners, are constantly evaluating whether new threats pose a risk to our food supply."
Spokesman Matt Herrick also said that "the public health relevance of these findings is unclear."
"As a public health regulatory agency, we will continue to review new data such as that presented in the study and determine if new information warrants changes in our policies to protect our nation's food supply. Our sole mission is to prevent food-borne illnesses and protect consumers from harm, and we are committed to that mission every day," he said.
Staphylococcus aureus has been linked to a variety of ailments, ranging from rashes to such potentially fatal illnesses as sepsis, endocarditis and pneumonia, according to the study's authors.
The bacteria can be killed by thoroughly cooking meat and poultry. However, consumers can still be at risk because of cross-contamination and improper handling of the food, according to the study.
The report pointed to large commercial farming operations that rely on providing animals low doses of antibiotics as "ideal breeding grounds for drug-resistant bacteria that move from animals to humans."
"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.
The federal government regularly examines meat and poultry for contamination from four strains of drug-resistant bacteria. Staphylococcus aureus is not one of them, according to the report.
The nationwide study was conducted by the Translational Genomics Research Institute in Phoenix, Arizona, and was funded by The Pew Charitable Trusts by way of The Pew Campaign on Human Health and Industrial Farming.
CNN's Samuel Gardner III contributed to this report.