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.”
“The No. 1 misunderstanding about antibiotics in animal agriculture is that it is not understood well enough that antibiotics are used to keep animals healthy, period,” said Randall Singer, a professor of veterinary science at the University of Minnesota.
Professor Singer noted the limited number of samples in the federal data, 480 samples each of ground turkey, pork chops and ground beef, and chicken breasts, wings and thighs, compared with the huge amount of meat sold in the United States. “We should not assume that when we find resistance to antibiotics in humans, it means it was caused by the use of antibiotics in animals,” he said.
Many animals grown for meat are fed diets containing antibiotics to promote growth and reduce costs, as well as to prevent and control illness. Public health officials in the United States and in Europe, however, are warning that the consumption of meat containing antibiotics contributes to resistance in humans. A growing public awareness of the problem has led to increased sales of antibiotic-free meat.
The Agriculture Department has confirmed that almost 80 percent of all antibiotics sold in the United States are used in animal agriculture, and public health authorities around the world increasingly are warning that antibiotic resistance is reaching alarming levels.
“We don’t have a problem with treating animals with antibiotics when they are sick,” Ms. Undurraga said. “But just feeding them antibiotics to make them get bigger faster at a lower cost poses a real problem for public health.”
The F.D.A. has recommended that the use of antibiotics in farm animals be “limited to those uses that are considered necessary for assuring animal health,” but its guidance is only voluntary.
Supermarkets increasingly are labeling meat that does not contain antibiotics, just one sign of the growing consumer awareness of the issue.
The federal researchers tested for the enterococcus bacteria, which is an indication of fecal contamination. Enterococcus also easily develops resistance to antibiotics, and it easily can pass that resistance on to other bacteria.
Two species of the bacteria, Enterococcus faecalis and Enterococcus faecium, are the third-leading cause of infections in the intensive care units of United States hospitals.
Some 87 percent of the meat the researchers collected contained either normal or antibiotic-resistant enterococcus, suggesting that most of the meat came in contact with fecal material at some point.
“That’s a big percentage they’re throwing around, but that organism itself on food or in an animal has little or no relationship to human health,” Professor Singer said.
Of the chicken breasts, wings and thighs the monitors tested, 9 percent of the samples were contaminated with a variety of salmonella that resists antibiotics, while 26 percent contained antibiotic-resistant campylobacter.
Ten percent of the ground turkey tested contained resistant salmonella.
More stark was the proportion of microbes identified that were resistant. Of all the salmonella found on raw chicken pieces sampled in 2011, 74 percent were antibiotic-resistant, while less than 50 percent of the salmonella found on chicken tested in 2002 was of a superbug variety.
This article has been revised to reflect the following correction:
Correction: April 24, 2013
An article last Wednesday about a report that found a sizable increase in the amount of meat contaminated with antibiotic-resistant forms of bacteria misstated part of the name of the organization that issued it. It is the Environmental Working Group, not the Environmental Work Group.
