Antibiotics in Your Food: What’s Causing the Rise in Antibiotic-Resistant Bacteria in Our Food Supply

As the use of antibiotics in farming and raising livestock has increased, new antibiotic resistant bacteria, or "superbugs" are emerging. Here's what you need to know.

Last fall I flew halfway across the country to go grocery shopping with Everly Macario. We set out from her second-story apartment in Hyde Park near the University of Chicago and walked to the supermarket to buy a couple of rib steaks that Macario planned to serve to her husband and two children, ages 7 and 13. Macario, who is 46, holds a doctorate in public health from Harvard University and has spent decades as a consultant, working to prevent deaths from chronic conditions such as cancer and cardiac disease.

Yet she believes that what she buys—or more accurately, refuses to buy—in the supermarket is the most important action she takes, not only for her family’s health but for the health of every person in this country. “I am determined that no product from an animal that has been fed antibiotics will ever enter my home,” she said as we walked along the meat counter peering at beef, poultry and pork. “I look for labels that read ‘certified organic,’ ‘no antibiotics’ or ‘raised without antibiotics.’”

It’s not the antibiotics themselves that are troubling: animals pass the drugs through their systems long before they are slaughtered and animal products are tested for traces of antibiotics. What really worries Macario is the increasing wave of antibiotic-resistant bacteria that might be traveling on her food.

Macario has reason to be vigilant. Her 18-month-old son, Simon, died in 2004 from an infection known as methicillin-resistant Staphylococcus aureus (or MRSA, pronounced “mersa”). Simon was a husky, happy toddler. On his first birthday, Macario marveled to her husband that the baby had never been sick. Then one morning the boy awoke with, in Macario’s words, a “blood-curdling shriek.” Rushed to the hospital, Simon was put on a heart-lung machine. “The doctors administered every available antibiotic,” she said. “It didn’t work. The bacteria were resistant to all of the medication.” In less than 24 hours he was dead. “The bacteria released toxins that destroyed his vital organs,” Macario said.

No one knows how Simon contracted the bacteria. He had never been to a hospital, once thought to be the primary incubators of MRSA. He had a robust immune system. He wasn’t in child care. He had no cuts through which the bacteria could infect him. The germs that killed him were “community-acquired” MRSA-CA, meaning that he came in contact with them through everyday living, as opposed to “hospital-acquired” MRSA, a strain that is associated with medical centers and nursing homes.

While it remains unclear how MRSA infected Simon, what is known is that these antibiotic‑resistant bacteria are on the rise. According to the Centers for Disease Control and Prevention, the incidence of MRSA in the United States more than doubled between 1999 and 2005, from 127,000 to 280,000, and MRSA-related deaths rose from 11,200 to 17,200. Perhaps it’s no coincidence that while the quantity of antibiotics given to humans has remained stable, the amount fed to livestock has soared. According to Food and Drug Administration records, antibiotic use on farms grew from about 18 million pounds in 1999 to nearly 30 million pounds in 2011.

Today 80 percent of the antibiotics used in the United States are fed to livestock. Theirs is a diet laced with low “subtherapeutic” doses of antibiotics, not to cure illness but to make the animals grow faster and survive cramped living conditions. The low doses kill many bacteria, but some develop mutations that make them immune to the same drugs that once destroyed them.

“It is very hard to prove that a specific antibiotic given to an animal for food production led to the development of a resistant bacterium in a specific patient,” said Stuart Levy, M.D., president of the Alliance for the Prudent Use of Antibiotics and a professor at Tufts University School of Medicine. “But it is a truism that antibiotic use leads to resistance, and the more antibiotics you use, the more resistance you get.”

By avoiding foods from animals that have been fed antibiotics, Macario believes she is doing more than just protecting her family from direct exposure to these “superbugs.” She is attacking the plague at its source.

That Which Does Not Kill Me…

It’s hard to imagine that until World War II, infectious diseases such as pneumonia and tuberculosis were dreaded killers in this country. Beginning with the introduction of penicillin in the 1940s, these scourges could finally be cured with antibiotics. It was nothing short of a miracle. But scientists have always been aware that the miraculous antibiotics could become useless if they were underdosed and failed to knock out an infection completely. Bacteria are reproductive dynamos; a single Staph can divide every 30 minutes, meaning that one resistant bacterium is able to erupt into a colony of more than 1 million in less than a day. In the presence of a nonlethal dose of antibiotics, bacteria can mutate to become resistant, breeding a new strain. Which is exactly what began to happen on farms across the U.S.

In the early 1950s, drug companies began marketing antibiotics for livestock after studies showed that low doses of penicillin, tetracycline, bacitracin and other drugs used to cure infections in humans made animals grow more quickly. Unfortunately, within two decades there was persuasive scientific evidence that the low-dose antibiotics were a recipe for disaster. In a seminal 1976 study, Levy administered small amounts of the antibiotic tetracycline to a flock of chickens. Soon, the chickens were carrying E. coli bacteria that were resistant not only to tetracycline, but to other antibiotics as well. Within weeks, the farmers who tended those birds also carried resistant bacteria.

A year later (1977), the Food and Drug Administration, the federal agency mandated to protect Americans’ health, announced plans to ban feeding livestock low doses of antibiotics, which, according to the FDA, had not been “shown safe for widespread, subtherapeutic use.” But bowing to pressure from legislators and agribusiness, the FDA failed to act on its recommendation, even after the American Academy of Pediatrics, the Centers for Disease Control and Prevention, the National Academy of Sciences, the U.S. Department of Agriculture and the World Health Organization identified subtherapeutic use of antibiotics as a human health issue. More than 30 years later, when the Natural Resources Defense Council and other groups sued in 2011, the FDA revoked its recommendation and said that a “voluntary” effort would be more effective.

Hog Heaven, Hog Hell

If there is a ground zero for the abuse of antibiotics in the United States, it’s probably Iowa, where hogs outnumber humans seven to one. During the 90-minute drive up I-35 from Des Moines to visit one farm, I was rarely out of sight of rows of long, low barns—each home to at least 2,000 pigs confined shoulder-to-shoulder in pens—known as CAFOs (Concentrated Animal Feeding Operations). In 2009, Tara Smith, Ph.D., a researcher at the University of Iowa, published a study that found that nearly half of the hogs at two large Iowa farms carried MRSA. More worrisome, 45 percent of the workers at those farms harbored the bacteria.

A study published in 2011 by the Translational Genomics Research Institute showed that MRSA was finding its way into our meats. Researchers analyzed 136 samples of beef, poultry and pork from 36 supermarkets in California, Illinois, Florida, Arizona and Washington, D.C. Nearly one-quarter of the samples tested positive for MRSA.

A Plague of New Superbugs

And it’s not only MRSA. During studies that lasted from 2005 to 2012, Amee Manges, a researcher at McGill University, found that supermarket chicken in Ontario and Quebec carriedE. coli bacteria that bore a close genetic relation to strains that caused stubborn, drug-resistant urinary tract infections in 350 women she examined in Montreal. In 2011, antibiotic-resistantSalmonella in ground turkey sold by Cargill sickened 136 consumers in 35 states, killing one. An examination of pork chops and ground pork published by Consumer Reports in 2012 showed that almost two-thirds of samples tested positive for resistant Yersinia enterocolitica, a bacterium that causes food poisoning. Some meat was also contaminated with drug-resistant SalmonellaStaphylococcus and Listeria. While cooking meat properly will kill bacteria, every year thousands of people are sickened by them, and for some (especially the very young, the very old and those with weak immune systems) the illnesses can be fatal.

“We are calling on retailers and grocery stores… to commit to stopping these practices and stocking only meat that was raised without feeding antibiotics to healthy animals,” Jean Halloran, director of food policy initiatives at the Consumers Union, said in a statement accompanying the release of the report.

Companies that sell the drugs used on livestock deny that there is a connection between resistant bacteria found in animals and humans. “There isn’t sufficient data to draw the conclusions drawn by Consumer Reports that attribute resistant bacteria in pork to the animals receiving antibiotics,” said Ron Phillips, vice president for legislative and public affairs at the Animal Health Institute, a trade group representing Bayer, Merck and other pharmaceutical companies. “Resistant bacteria are out there and can come from a lot of different sources. In fact, there have been numerous studies over the past decade that have examined potential pathways for antibiotic-resistant material to transfer from animals to humans.”

Phillips contends: “Several of these assessments have been done on different kinds of antibiotics and each and every one of them, including one performed by the FDA itself, have come to the conclusion that there is a vanishingly small level of risk.”

But it is virtually impossible to find a microbiologist unaffiliated with industry who agrees with him. “There are decades of evidence linking antibiotic use in food production with the emergence of drug resistance,” said Lance B. Price, a professor at George Washington University’s School of Public Health and Health Services. “There’s very clear, sound science showing that the multi-drug-resistant strains emerged from drug use in food animal production then spread to humans. Anyone saying that there’s no data is either deceiving themselves or lying.”

Price led a team of 33 researchers from 19 countries who tracked the origins and evolution of Staphassociated with pigs and other meat animals. They discovered a nonresistant strain of Staph that originated in humans and was transmitted to livestock. There, it quickly became resistant to antibiotics and was passed back to humans as a virulent form of MRSA, according to a paper they published in 2012.

A Better Solution?

Supermom and DaughterSo could keeping antibiotics off the farm keep humans out of the hospital? In 2009, Tara Smith of the University of Iowa sought to answer that question. As part of the study, she took nasal swabs from Sarah Willis, Willis’s 11-year-old daughter, mother and father and their farm workers to test for MRSA. Smith was interested in the family because Sarah’s father, Paul Willis, founded Niman Ranch’s pork collective in the late 1990s. The operation has since grown to include more than 500 family farmers. Niman farmers never administer antibiotics to livestock nor do they confine their animals in CAFOs. On the day I visited Sarah Willis, the pigs on her family’s 800-acre property were playing chase with each other or snoozing in the late-autumn sunshine of their paddocks—a rare sight in Iowa.

Smith also tested nine other farmers who did not use antibiotics. And she tested nine farmers who did administer the drugs to their animals. The results? Even though all the farmers in her tests ran large, commercial pig operations, not one of the producers who avoided antibiotics tested positive for MRSA, while nearly half the farmers who routinely used antibiotics on their pigs carried resistant bacteria. In other words, avoiding the drugs on the farm might be one way of reducing the prevalence of these virulent strains.

The findings resonated with Sarah Willis. One of those pig CAFOs is less than a mile from her house. In 2011, there were seven cases of MRSA in her daughter’s school district. It took two rounds of antibiotic treatment to cure the youngsters. “I avoid meat raised on antibiotics due to health concerns,” Willis said. “But it’s more important to me that I am voting with my dollars. I would rather spend my money on food that is raised responsibly.”

The real tragedy of subtherapeutic antibiotic use is that it is unnecessary. Before joining Niman, Paul Willis administered antibiotics to his hogs. “And we had more health problems with our animals then than now,” he said, when Sarah and I met him at a cafe. “Going antibiotic-free is not only good for people, but animals as well.” Studies in Denmark, a major pork-producing country that banned subtherapeutic antibiotics in 2000 (followed by the rest of the European Union in 2006), confirm Paul Willis’s observations. In Denmark, incidences of resistant bacteria fell dramatically, in both people and animals, after the ban. Pork production rose.

A Demand for Drug-Free

For Willis, though, “it was a customer issue. My biggest customers pushed for the animals to be free from antibiotics, so I banned drugs.” Companies that now refuse to sell meat produced with antibiotics include Whole Foods Market and Chipotle Mexican Grill, and the list is growing. Hyatt Hotels now offers antibiotic-free options at all its restaurants. At a time when sales of most meat and poultry products are flat, antibiotic-free-meat sales are climbing at a rate of 10 to 15 percent annually and sales from antibiotic-free pork alone now approach $500 million a year, according to Kevin Kimle, a faculty member in the economics department at Iowa State University.

Everly Macario is convinced that conscientious shoppers are the key to boosting those numbers. “If we buy only antibiotic-free meat, then demand for conventional meat will drop and more farmers will stop drugging their animals. It’s something every shopper can do.” She does not stop at shopping: Macario helped found the MRSA Research Center at the University of Chicago Medical Center. She also became the leader of Supermoms Against Superbugs, which met with food-policy legislators in Washington, D.C., in 2012 to discuss ways to keep antibiotics viable.

But to date, there has been no solid progress. Congresswoman Louise Slaughter, a Democrat from upstate New York and a microbiologist by training, has repeatedly tried to legislate limits on the use of the drugs in animals, without success. In an email, Slaughter said, “With the threat of antibiotic resistance higher than ever, I will once again introduce the Preservation of Antibiotics for Medical Treatment Act at the start of the 113th Congress. As the science continues to make clear, there is no more time for delay.”

Macario is frustrated. But while the FDA stonewalls and Congress dithers in the face of intense lobbying from agribusiness and pharmaceutical companies, there is one way to effect change.

“I love meat,” Macario said during our visit to the supermarket. “I crave it. I’m originally from Argentina. My grandfather raised cattle.” At the store, Macario zeroed in on Rain Crow Ranch grass-fed steaks. The package was not labeled “antibiotic-free,” but Macario had researched the company and its farms and was confident that they never used antibiotics. The steaks, at $21.99 a pound, were pricier than the same cuts raised with antibiotics (though the Consumer Reports survey found that many antibiotic-free meats cost the same or in some cases less). All the other meats, dairy products and eggs she chose had similar assurances of avoiding antibiotics.

“When I shop for food, I always try to remember what one consumer advocate in Washington told me,” Macario said. “Congress and big agricultural interests are scared to death of moms.”

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