Superbugs Invade American Supermarkets
Antibiotic-resistant bacteria are now common in the meat aisles of American supermarkets. These so-called superbugs can trigger foodborne illness and infections that are hard to treat.
An analysis by the Environmental Working Group has determined that government tests of raw supermarket meat published last February 5 detected antibiotic-resistant bacteria in:
These little-noticed tests, the most recent in a series conducted by the National Antimicrobial Resistance Monitoring System, a joint project of the federal Food and Drug Administration, Centers for Disease Control and Prevention and U.S. Department of Agriculture, found that supermarket meat samples collected in 2011 harbored significant amounts of the superbug versions of salmonella and Campylobacter, which together cause 3.6 million cases of food poisoning a year.
Moreover, the researchers found that some 53 percent of raw chicken samples collected in 2011 were tainted with an antibiotic-resistant form of Escherichia coli, or E. coli, a microbe that normally inhabits feces. Certain strains of E. coli can cause diarrhea, urinary tract infections and pneumonia. The extent of antibiotic-resistant E. coli on chicken is alarming because bacteria readily share antibiotic-resistance genes.
Not surprisingly, superbugs spawned by antibiotic misuse -- and now pervasive in the meat Americans buy -- have become a direct source of foodborne illness. Even more ominously, antibiotic misuse threatens to make important antibiotics ineffective in treating human disease. In the past, people who became ill because of contact with harmful microbes on raw meat usually recovered quickly when treated with antibiotics. But today, the chances are increasing that a person can suffer serious illness, complications or death because of a bacterial infection that doctors must struggle to control.
The proliferation of antibiotic-resistant bacteria poses special dangers to young children, pregnant women, the elderly and people with weakened immune systems.
Among the most worrisome recent developments:
- The federal tests published in February determined that 9 percent of raw chicken samples and 10 percent of raw ground turkey sampled from retail supermarkets in 2011 were tainted with a superbug version of salmonella bacteria. Antibiotic resistance in salmonella is growing fast: of all salmonella microbes found on raw chicken sampled in 2011, 74 percent were antibiotic-resistant, compared to less than 50 percent in 2002. These microbes, frequently found on chicken and turkey and occasionally on beef and pork, commonly cause diarrhea and in extreme cases can lead to arthritis.
- In the same federal tests, a superbug version of the Campylobacter jejuni microbe was detected on 26 percent of raw chicken pieces. Raw turkey samples contained numerically fewer of these microbes, but 100 percent of those examined were antibiotic-resistant. The Campylobacter jejuni pathogen is a common cause of diarrhea and in severe cases can trigger an autoimmune disease that results in paralysis and requires intensive care treatment.
- In 2006 FDA scientists found superbug versions of a particularly troublesome strain of E. coli, responsible for more than 6 million infections a year in the U.S., on 16 percent of ground turkey and 13 percent of chicken. Fully 84 percent of the E. coli bacteria identified in these tests were resistant to antibiotics.
- In its own tests of raw pork, published last January, Consumer Reports magazine found that 63 percent contained a superbug version of Yersinia enterocolitica, a microbe that can cause long-lasting bouts of diarrhea.
- In 2011 tests, researchers at Northern Arizona University and the Translational Genomics Research Institute found that 74 percent of store-bought raw turkey samples were tainted with Staphylococcus aureus bacteria resistant to at least one antibiotic. Of these staph bacteria, 79 percent were resistant to three or more types of antibiotics. Staph can cause skin infections in exposed cuts or produce toxins that cause foodborne illness.
A significant contributor to the looming superbug crisis, according to scientists and health experts, is unnecessary antibiotic usage by factory farms that produce most of the 8.9 billion animals raised for food in the U.S. every year. Industrial livestock producers routinely dose their animals with pharmaceuticals, mostly administered with limited veterinary oversight and frequently without prescriptions, to encourage faster growth or prevent infection in crowded, stressful and often unsanitary living conditions.
Overuse of antibiotics in people, often for colds and other viral illnesses, has contributed to antibiotic resistance, too, but responsible doctors generally take care not to prescribe them unnecessarily.
Pharmaceutical makers have powerful financial incentives to encourage abuse of antibiotics in livestock operations. In 2011, they sold nearly 30 million pounds of antibiotics for use on domestic food-producing animals, up 22 percent over 2005 sales by weight, according to reports complied by the FDA and the Animal Health Institute, an industry group. Today, pharmaceuticals sold for use on food-producing animals amount to nearly 80 percent of the American antibiotics market, according to the Pew Campaign on Human Health and Industrial Farming. Pew calculates that the market for antibiotics for treatment of people has been flat for some years, hovering at around 7.7 million pounds annually.
As the superbug problem has exploded into a full-fledged global health crisis, medical authorities worldwide are sounding increasingly urgent alarms.
The federal government's Interagency Task Force on Antimicrobial Resistance warned last year that “drug choices for the treatment of … infections are becoming increasingly limited and expensive, and, in some cases, nonexistent.”
Also last year, Dr. Margaret Chan, director general of the World Health Organization, said that if important antibiotics become useless, “things as common as strep throat or a child's scratched knee could once again kill.”
Slowing the spread of antibiotic resistance will require concerted efforts, not only by doctors, patients and veterinarians but also livestock producers and big agribusinesses.
Antibiotics, the lifesaving drugs that treat bacterial infections, came into widespread use after World War II, laying the groundwork for modern medicine.
Along the way, livestock producers discovered that giving antibiotics to healthy pigs and chickens made them gain weight faster. Yet now scientists know that feeding antibiotics to healthy animals over time, especially in low doses, kills weak bacteria, allowing strains that can withstand the drugs to evolve and become dominant.
Bacteria that develop resistance to one antibiotic can often tolerate another, or several others. They can pass this trait not only to their offspring but to other microbes of different species.
Industrial-scale animal production is an ideal climate for breeding superbugs. It offers an environment in which bacteria can develop antibiotic resistance and spread it via human workers, animals, water, soil and air. Superbugs can travel on meat to stores - and into kitchens, where food safety missteps can make people sick.
Superbugs in meat
EWG's research has determined that the risk of bringing a superbug into a kitchen varies by type of meat and how it was raised. Some types of meats are more contaminated than others. The overall picture is disturbing.
In the most recent round of federal tests, scientists used Enterococcus bacteria, normally found in human and animal intestines, as a gauge. For one thing, their presence can indicate contact with fecal matter. For another, Enterococcus bacteria easily develop and transmit antibiotic resistance. Counting the number of antibiotic-resistant Enterococcus on a particular meat sample can signal that other microbes on the meat are also likely antibiotic-resistant.
The scientists determined that startlingly high percentages of store-bought meat samples were contaminated with antibiotic-resistant forms of Enterococcus faecalis.
Enterococcus faecalis and the related species Enterococcus faecium are the third leading cause of infections in intensive care units of American hospitals.
Fully 87 percent of store-bought meat collected by federal scientists in the most recent round of tests was contaminated with both normal and antibiotic-resistant Enterococcus bacteria, evidence that most of this meat likely came in contact with fecal matter at some point. To be safe, consumers should treat all meat as if it may be contaminated, mainly by cooking thoroughly and using safe shopping and kitchen practices (see EWG's downloadable Tips to Avoiding Superbugs in Meat).
Super Salmonella on the rise
Salmonella bacteria are often found on chicken and turkey that have been contaminated with animal feces. People can also encounter these microbes through cross-contamination - for instance, when salad greens are sliced on a cutting board that has been used to chop raw meat -- or by touching infected birds or reptiles. Infants have been known to contract salmonella by touching raw meat in a shopping cart. Salmonella-caused illnesses kill 400 people a year and cause 23,000 hospitalizations. They can lead to chronic arthritis.
The rise of antibiotic-resistant salmonella has heightened the risks that people will succumb to severe infection, hospitalization and death. In less than a decade, the proportion of antibiotic-resistant salmonella bacteria found on raw chicken has dramatically increased - from 48 percent in 2002 samples to 74 percent in 2011 samples.
About 20 percent of the salmonella microbes detected on chicken samples collected in 2002 were resistant to at least three drugs. By 2011, that number had risen to 45 percent. The proportion of antibiotic-resistant germs among all salmonella found on raw turkey rose from 62 percent in 2002 to 78 percent in 2011.
Super Campylobacter on the rise
Campylobacter is one of the most common causes of diarrheal illness in the U.S. As well, it can trigger Guillain-Barre syndrome, an autoimmune disease that usually requires intensive care treatment and can lead to paralysis. Campylobacter germs cause 2.4 million foodborne illnesses and 124 deaths a year. The CDC reports that the rate of Campylobacter infections per 100,000 population increased by 14 percent between 2006-2008 and 2011.
The most recent round of federal meat tests found that 26 percent of raw chicken pieces contained an antibiotic-resistant form of Campylobacter. Of all the Campylobacter microbes found on the raw chicken samples, 58 percent were resistant to at least one antibiotic, and 14 percent were resistant to several antibiotics. Most alarmingly, all Campylobacter found on turkey were resistant to at least one antibiotic.
For more than 40 years, scientists and health experts have known that dangerous microbes were developing the ability to defeat valuable drugs. As far back as 1970 the FDA concluded that dosing livestock with unnecessary antibiotics spurred development of superbugs. Last year, the agency recommended that important antibiotics in farm animals “should be limited to those uses that are considered necessary for assuring animal health.” It said that dosing animals with drugs solely to promote growth was “an injudicious use of these important drugs.”
Nevertheless, the FDA's efforts to curb antibiotic abuse consist of only voluntary guidance documents - not regulations that carry the force of law. EWG takes the position that the FDA must take more aggressive steps to prevent superbugs from proliferating and livestock producers from squandering the effectiveness of vital medicines.
Big agribusinesses must take responsibility for their actions by exercising the same restraint shown by good doctors and patients: use antibiotics only by prescription for treatment or control of disease.
EWG recommends that consumers assume that all meat is contaminated with disease-causing bacteria. They can avoid superbugs in meat by eating less factory-farmed meat, by buying meat raised without antibiotics and by following other simple tips in EWG's downloadable Tips to Avoiding Superbugs in Meat.
For more information on the health and environmental consequences of various meats, see ewg.org/meateatersguide.
Make your voice heard! Click here to find out how you can help preserve the effectiveness of antibiotics.
This guide was developed by EWG's Dawn Undurraga, nutritionist, Johanna Congleton, senior scientist, and Renee Sharp, director of research. Content was reviewed by Kari Hamerschlag, senior analyst, Brett Lorenzen, Mississippi River project coordinator, and Andrew Hug, analyst. It was edited by Elaine Shannon, editor-in-chief and publisher and Nils Bruzelius, executive editor and vice president for publications, and designed by EWG web designers Aman Anderson and Taylan "Ty" Yaniz. The authors thank Katie Clark and Lisa Frack for their assistance.
Thanks to those who reviewed and provided valuable feedback:
- Andrew Gunther, program director, Animal Welfare Approved
- Gail Hansen, senior officer, The Pew Charitable Trusts
- Avinash Kar, attorney, Natural Resources Defense Council
- Aaron Kornbluth, senior associate, The Pew Charitable Trusts
- Lance Price, Ph.D, director, Center for Food Microbiology and Environmental Health, Translational Genomics Research Institute
- Laura Rogers, project director, The Pew Charitable Trusts
We thank Applegate Organic & Natural Meats for helping make this guide possible through an educational grant.
The opinions expressed in this report are those of the authors and do not necessarily reflect the views of funders or reviewers.