The Director-General of the World Health Organization was blunt. The world is facing “an end to modern medicine as we know it,” Margaret Chan warned last year. Strep throats could once again kill people, and hip replacements, organ transplants, and cancer chemotherapy “would become far more difficult or even too dangerous to undertake.” That’s because we’re losing our first-line antimicrobial drugs to antibiotic resistance, Chan noted. As for new antibiotics to replace them, Chan wasn’t optimistic: “The pipeline is virtually dry. The cupboard is nearly bare.”
On the evening before Halloween in 2011, Danielle Wadsworth, a healthy 31-yearold insurance agent, shared a dinner of beef tacos with friends at her home in Lewiston, Maine.“Then, seemingly out of nowhere, I started feeling like I had the flu,” she told the Web site keepantibioticsworking.com.
By the next day, “I just wanted to be left alone.”
But Wadsworth got worse. When her persistent bloody diarrhea wouldn’t stop, she went to the emergency room, where intravenous fluids brought temporary relief. But when the bloody diarrhea returned, she ended up back in the hospital.For the next four days, as she suffered intense pain and alternating pangs of hunger and thirst, Wadsworth was treated with morphine every few hours while her doctors tried to figure out what was wrong.
“I love life, but was beginning to wonder if fighting was worth it,” she recalled. “It never crossed my mind that it could be something I’d eaten.”
Nor did that occur to the hospital staff until the stool cultures came back positive for Salmonella typhimurium, one of the leading causes of food poisoning in the United States.
Wadsworth was one of 20 known victims infected with a new strain of S. typhimurium, one that was resistant to at least eight antibiotics, including streptomycin and tetracycline. The Centers for Disease Control and Prevention (CDC) eventually traced the resistant S. typhimurium to contaminated ground beef sold by a supermarket chain, but the CDC couldn’t identify the meat supplier because the chain hadn’t kept good records.
Fortunately, the bug was still susceptible to the antibiotic ciprofloxacin. Cipro helped cure Wadsworth’s infection, but it couldn’t heal the anxiety that she says she still feels about what can happen from eating tainted food.
Or what could happen to her loved ones. “I am the legal guardian for my grandfather. Considering that I cook for him, I hate to even think about the outcome had he eaten the same meat that made me sick.”
ANTIBIOTIC-RESISTANT BUGS GALORE
The seven-state outbreak that sickened Danielle Wadsworth was one of 55 food poisoning outbreaks since 1973 that were caused by antibiotic-resistant bacteria, according to a new report by the Center for Science in the Public Interest (publisher of Nutrition Action Healthletter).1
More than two-thirds of the bacteria fingered in those outbreaks were resistant to antibiotics that the World Health Organization considers “critically important” for treating humans or that the Food and Drug Administration (FDA) regards as “highly important.”
Of the 55 outbreaks, 14 involved dairy foods (usually raw milk or raw-milk cheese), while 10 came from ground beef, 7 from poultry, 4 from produce, 2 from seafood, 1 each from pork and eggs, and 3 from multiple ingredients. (In 13 of the outbreaks, no specific food could be identified.) Antibiotic-resistant Salmonella typhi murium, the bug that made Danielle Wadsworth so sick, was the bacterium found most often.
COURSE OF MOST RESISTANCE
“There’s this huge population of antibiotic resistance genes in bacteria in nature and nobody quite knows why they’re there,” says microbiologist Julian Davies of the University of British Columbia in Vancouver. “You can even find them in caves where no human has ever been.”
“What we do know,” explains Lance Price, an environmental health scientist at George Washington University in Washington, D.C., “is that when you use antibiotics, it’s very clear and undisputable that you promote the development of drug-resistant bacteria. It’s one of the strongest evolutionary forces in nature.”
Antibiotics stop bacteria by killing them or halting their growth. Resistant bacteria have genes that enable them to survive certain antibiotics by neutralizing the drugs, by pumping the drugs out of their cells, or by altering the cell structure that the antibiotic attacks so that it’s no longer vulnerable.
To make matters worse, bacteria can swap their resistance genes with each other, so that the instructions for resistance are passed on to other bacteria that have yet to be exposed to the antibiotic.
Every time an antibiotic is used, susceptible bacteria are killed, paving the way for resistant bugs to grow and multiply.
The consequences can be deadly. “People sickened by antibiotic-resistant bacteria are more likely to have longer and more expensive hospital stays, and may be more likely to die as a result of the infection,” Price notes. And these aren’t obscure bacteria, he adds. “They’re the same kind of E. coli, for instance, that cause urinary tract infections and sepsis, or blood infections.”
When the first-choice antibiotics are useless, physicians have to resort to drugs that may be less effective, more toxic, and more expensive, according to the CDC.
Unfortunately, much of the damage to the effectiveness of antibiotics has already occurred.
“There’s no doubt that antibiotic resistance is now widespread throughout the world,” says Davies.
A major cause: the chronic misuse of antibiotics in hospitals, physicians’ offices, and homes. Some doctors, for example, still prescribe—and some patients still demand—antibiotics to treat colds or the flu, even though both are caused by viruses, not bacteria. (Antibiotics don’t attack viruses.)
“Humans are to blame in large part for creating this huge problem,” says George Zhanel, a microbiologist at the University of Manitoba and director of the Canadian Antimicrobial Resistance Alliance.
But reducing the inappropriate use of antibiotics in human medicine alone won’t be enough, concluded a 2003 report from the National Academy of Sciences.2 “Substantial efforts must be made to decrease inappropriate overuse of antimicrobials in animals and agriculture as well.”
That’s because three-quarters of the antibiotics that are used in the United States are given to animals, not people.
ANTIBIOTICS TO GROW ON
Most meat and poultry farms rely on antibiotics to treat sick animals and to prevent healthy animals from becoming sick. Modern facilities crowd many animals together, which makes it easier for disease to spread throughout the herds or flocks. (Antibiotics are also widely used in fish farming.)
“The antibiotics approved by the FDA for use in animals represent nearly every class of antibiotic important for treating humans,” says Price.
Much of the antibiotics that are given to animals, however, are not to treat or prevent disease, but to stimulate growth.
In the 1950s, scientists discovered that animals fed small, “sub-therapeutic” doses of antibiotics grew more quickly on the same amount of food. And farmers need no prescription for those low doses.
“It’s a big economic advantage because the animals are larger and healthier, and their time to slaughter is shorter,” explains Zhanel. “The drawback is that this use of antibiotics selects out anti bioticresistant bacteria for survival.”
For example, fluoroquinolone antibiotics (which include the Cipro that helped Danielle Wadsworth) can kill a wide range of disease-causing bacteria. After the FDA approved their use in poultry in 1995, resistance to fluoroquinolones among Campylobacter bacteria on chickens tested at slaughter houses and supermarkets rose so sharply that in 2000, the FDA reversed its decision and tried to ban the use of fluoroquinolones in poultry. (The ban was delayed for five years while Bayer, which manufactures fluoroquinolones, fought it unsuccessfully in court.)
RESISTANT BACTERIA SPREAD
Antibiotic-resistant bacteria usually reside in an animal’s intestines and are excreted in its waste. From there, they can be spread by polluted water, farm workers, the wind, birds, and even flies.
In North Carolina, for example, swine waste is commonly stored in open pits before being sprayed onto nearby fields. “Many of these waste pits are located in flood plains and can overflow, while the fields sprayed with waste can contaminate groundwater,” says epidemiologist Steve Wing of the University of North Carolina.
“This clearly is a potential source for human exposure to antibiotic-resistant bacteria.”
BUGS ON FOOD
Some antibiotic-resistant bacteria wind up on the meat and poultry in the refrigerator case at the supermarket.
“Our food supply is tainted with disease-causing bacteria that are often resistant to many different antibiotics,” says George Washington University’s Lance Price, who serves on a U.S. Department of Agriculture advisory panel on food safety.
The National Antimicrobial Resistance Monitoring System (NARMS), which consists of the FDA, the CDC, and about a dozen state public-health laboratories, buys chicken, ground turkey, ground beef, and pork chops at retail stores nationwide every year and tests them for antibiotic-resistant bacteria. It has no trouble finding them.
In 2011, the latest year available, NARMS detected Salmonella in 12 percent of the chicken samples that it tested. About three-quarters of the bugs were resistant to at least one antibiotic, and more than a quarter were resistant to at least five classes of antibiotics. That’s eight times the level of multiple resistance found in 2002.3
Salmonella also turned up in 12 percent of the ground turkey samples. About three quarters of the bacteria were resistant to at least one antibiotic, and 19 percent— double the percentage found in 2002—were resistant to at least five classes of antibiotics.
E. coli was detected in two-thirds of the beef and around 40 percent of the pork samples. Roughly half of the E. coli on pork and a fifth of the E. coli on beef were resistant to at least one antibiotic. About 1 percent of the E. coli on each meat was resistant to at least five classes of antibiotics. For beef, that’s triple the percentage found in 2002, and for pork, it’s one-third the level.
“The evidence is unequivocal that drug-resistant pathogens have contaminated meat and other animal foods and infected people with drug-resistant infections,” says Price. “What we don’t know is the full extent of it.”
ENDING DRUG ABUSE
How practical would it be to end the routine use of antibiotics to promote growth in animals that are raised for food? Very practical, says Price, because it’s already been done.
In the late 1990s, Denmark, the world’s largest exporter of pork, banned the use of antibiotics on farms except to treat sick animals.
“Nothing bad happened as a result,” Price notes. Ending the use of antibiotics for growth promotion caused no sustained harm to animal survival, production rates, or feed efficiency, a World Health Organization expert panel found.4
“And these are industrial farms,” adds Price. “They’re cleaner, the density of animals is lower, and the quality of life is a little better than in the U.S., but these are still highly efficient industrial farms.”
Most importantly, ending the routine use of antibiotics helped slash rates of resistance.
According to the Danish Veterinary and Food Administration, the percentage of Campylobacter bacteria in pigs that was resistant to antibiotics like erythromycin dropped from 80 percent before the ban to less than 20 percent. And the percentage of vancomycinresistant E. coli in broiler chickens plummeted from 75 percent to less than 5 percent.5
The ban also led to a decline in resistant bacteria isolated from the intestines of healthy Danes.
LOWER YOUR ODDS OF FOOD POISONING FROM ANTIBIOTIC-RESISTANT BACTERIA?
It may help to buy meat or poultry that comes from animals that were never given antibiotics. According to a 2012 Stanford University meta-analysis, conventionally produced chicken and pork were 33 percent more likely than organic chicken and pork to be contaminated with bacteria that were resistant to at least three antibiotics.
But that won’t guarantee that you—or your child or parent— won’t get a bout of antibiotic-resistant food poisoning.
“As a society, we have to say that antibiotics are too valuable for treating sick people and that we cannot afford to squander them as production tools for raising animals,” says Lance Price, an environmental health scientist at George Washington University in Washington, D.C.
“We’re talking about the future of medicine. We don’t have new drugs coming up through the pipeline. And even if we did, if we abuse them the same way, they’re going to be useless again very quickly.”
6 Ann. Intern. Med. 157: 348, 2012.
Sources: 2012 survey by Rep. Louise Slaughter of New York, companies.
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