More than half of samples of ground turkey, pork chops and ground beef collected from supermarkets for testing by the federal government contained a bacteria resistant to antibiotics, according to a new report highlighting the findings.

The data, collected in 2011 by the National Antimicrobial Resistance Monitoring System — a joint program of the Food and Drug Administration, the Agriculture Department and the Centers for Disease Control and Prevention — show a sizable increase in the amount of meat contaminated with antibiotic-resistant forms of bacteria, known as superbugs, like salmonella, E. coli and campylobacter.

The government published the findings in February, but they received scant attention until the Environmental Working Group issued its report, “Superbugs Invade American Supermarkets,” which was partly underwritten by Applegate, which sells organic and antibiotic-free “natural” meats.

“The numbers are pretty striking,” said Dawn Undurraga, the nutritionist for the group, a health research and advocacy organization. “It really raises a question about the antibiotics we are using in raising animals for meat.”