Nutrition Action Healthletter
May 2000 — U.S. Edition 
Magic Bullets Under Siege

Food poisoning is bad enough. But when your insides are making a beeline for the nearest exit and you go to the doctor for some relief, the last thing you need is an antibiotic that doesn’t work. Yet, increasingly, that’s what’s happening.

   Antibiotics—drugs that kill bacteria— account for much of our success in the war against infectious illness. But the miracle drugs of medicine are in danger.

   The more we use antibiotics—to treat humans and to promote growth in animals on factory farms—the more bacteria become resistant to those antibiotics. And much of that use is unnecessary.

   “Bacteria evolve at a frightening pace,” says expert Glenn Morris of the University of Maryland School of Medicine in Baltimore. “And we’re losing the battle.”

Q: What is antibiotic resistance?

A: It’s the ability of bacteria to resist being killed by an antibiotic. The bacteria evolve and acquire or develop new genes that protect them from being destroyed by the antibiotic. Then you go to the doctor with pneumonia or a serious diarrheal illness, and suddenly the bacteria are no longer being killed by the antibiotic that the doctor prescribes.

Q: So you get sicker before the doctor finds a drug that works?

A: Yes. But potentially more serious are patients in hospitals, where no antibiotic may work because some bacteria have become resistant to just about all our main antibiotics.

Q: Has that happened yet?

A: Yes. Vancomycin-resistant enterococci, or VRE, is one of several bacteria that are being seen with increasing frequency in hospitals and that are, at best, minimally responsive to antibiotics.

Q: So a patient infected with VRE might die?

A: Yes. Keep in mind that our bodies have evolved reasonable defense mechanisms, so a healthy young adult can frequently fight off an infection without major difficulty. But when you’re dealing with an older person or a young child or a person whose immune system may not be working that well, antibiotics can spell the difference between life and death.

Q: Why are bacteria becoming resistant to antibiotics?

A: Bacteria evolve in response to what’s happening in their environment. If there are antibiotics in the environment, most of the bacteria will be killed off. But every now and then a bacterium will acquire or develop the necessary genes to resist being killed by the antibiotics. This becomes a selective advantage, and the resistant bacteria are better able to live and multiply.

   So when you use antibiotics a lot, it is almost inevitable that ultimately the bacteria will figure out some way to avoid being killed.

Q: Haven’t we kept up by making new antibiotics?

A: Over the last five decades we’ve kept up. And it’s taken a while for the bacteria to acquire resistance. But antibiotics are being used with increasing frequency in hospitals, on outpatients treated by doctors, and in agriculture. And in each case there are examples of rapid recent emergence of resistance.


Q: How are antibiotics used in animals?

A: They’re used therapeutically—that is, to treat a specific infection—and they’re used subtherapeutically, which means at levels lower than are used to treat an infection, to promote growth.

   But think about how you treat a chicken. You don’t take one chicken out and give it a pill. You treat the entire flock of 15,000 chickens. Once resistant organisms get into the flock, given the close quarters, they tend to spread rapidly to all chickens. And if you administer an antibiotic therapeutically even once, potentially every flock that goes back into that chicken house is at risk for acquiring a resistant organism until the litter is changed. That could be anywhere from six months to three years, depending on the company.

   In other words, with factory farming, it doesn’t take much therapeutic use of antibiotics for resistant strains of bacteria to spread very rapidly.

Q: And they’re spreading to humans?

A: Yes. Campylobacter is the leading cause of bacterial food-borne disease in the U.S. You’re most likely to get it from chicken. There are probably more than two million cases—and hundreds of deaths—a year. And Ciprofloxacin—one of a class of antibiotics called quinolones—is an excellent drug for treating Campylobacter infections.

   But over the last decade the rates of Campylobacter resistance to quinolones have gone from one or two percent to 21 percent. As a physician, when resistance hits 21 percent, you have to stop using the antibiotic because there’s too great a chance that your patient has a resistant strain of bacteria, so he or she won’t be helped by the drug.

   Since 1995, when the Food and Drug Administration approved quinolones for use in poultry, the rates of resistance have gone up dramatically. In many ways it’s already too late. We’ve essentially lost the use of these very valuable drugs in human medicine.


Q: How do the resistant bacteria spread to people?

A: Campylobacter is a normal inhabitant of the chicken’s intestinal tract. When chickens go to market there is widespread contamination. Have you ever seen the stacks of cages on trucks going to market? When a chicken in the top cage defecates, the fecal material goes down on all the chickens to the bottom of the stack.

   Once the fecal material—which contains the resistant Campylobacter—gets on the feathers and then into the feather follicles, it becomes virtually impossible to get it out. That’s why, when chickens are slaughtered, there is inevitably some contamination of the surface of the meat. In the supermarket, anywhere from 40 to 95 percent of all chickens or chicken parts carry Campylobacter on their surface.

Q: And people don’t always cook their chicken thoroughly?

A: You can get sick from the Campylobacter if you eat undercooked contaminated chicken. But most people probably get infected by Campylobacter through cross-contamination. If you put the raw chicken on your counter and then you move the chicken and put your fresh lettuce where the chicken was, the resistant Campylobacter that are on the surface of the chicken can end up on the lettuce. Since you eat the lettuce without cooking it, the Campylobacter can get into your intestinal tract and make you sick.

   People need to be aware that raw chicken is frequently contaminated with Campylobacter and other bacteria. You have to treat it with respect. The kicker now is that not only are Campylobacter causing disease, but there’s one chance in five that the bacteria won’t be killed by Ciprofloxacin, the antibiotic that physicians have traditionally used to treat it.

Q: What can doctors do?

A: With Campylobacter, the alternative antibiotic is erythromycin. The problem is that erythromycin tends to upset your stomach, which is not exactly what you want when you’ve got GI problems from a Campylobacter infection. Nonetheless, erythromycin does work…at least for now.

   But at the back of my mind is this concern: Will Campylobacter remain treatable five or ten years from now? Fortunately, Campylobacter is less likely to kill people than Salmonella. Unfortunately, we’re seeing suggestions of decreased susceptibility to quinolones in Salmonella bacteria, which you can also get from eating undercooked contaminated chicken.

   So wherever we look, we’re seeing increasing problems—not just in one organism or one drug. It’s multiple organisms and multiple drugs that give us this sense of foreboding.


Q: How can the use of antibiotics to promote growth in animals harm humans?

A: The best example is virginiamycin, an antibiotic that has been used for a number of years subtherapeutically as a growth enhancer in poultry. Not unexpectedly, we find a high level of resistance to it in enterococci, which are bacteria that are common in the intestinal tract of poultry.

   We always assumed that virginiamycin would never be used in human medicine. But then we were faced with vancomycin-resistant enterococci in hospitals. Those infections are untreatable with any antibiotic except a variant of virginiamycin called Synercid, which is usually able to kill the resistant bacteria.

Q: So suddenly people needed Synercid?

A: Yes, because we’d lost all our other drugs to treat vancomycin-resistant enterococci. In 1999, Synercid was licensed for use in humans. The problem is that when we screen normal, healthy adults, we find that about one percent are already carrying bacteria with resistance genes to Synercid. While we don’t know for certain where those genes come from, one possibility is poultry. Since genes that are resistant to Synercid are already in humans, as we begin to use Synercid, we may find a rapid increase in resistance in human enterococci.

Q: Can residues of the antibiotics that are given to animals end up in the meat and chicken sold at the supermarket?

A: No. The residues are trivial or nonexistent.

Q: Genetically modified foods contain antibiotic-resistance genes. Can the genes cause resistance in the bacteria in our gut when we eat those foods?

A: There is no evidence that this happens.

Q: Should we stop using human antibiotics on farms?

A: We should restrict them. Subtherapeutic use of antibiotics is clearly the best way to develop resistance becuase you're giving the bugs just enough antibiotic to promote their evolution, but not to kill them.

   The more basic question is whether it is appropriate to be using subtherapeutic levels of any antibiotics in agriculture. Europe has cut out the subtherapeutic use of antibiotics. But U.S. agricultural producers argue that the U.S. is not Europe, because Europe generally has smaller operations. So it’s an extremely complex issue.

   Therapeutic uses are also complex. If chickens are sick, we should treat them. But the FDA approved quinolone use on that logic, and now we have a major problem with resistance in humans.



Q: Why are we using more antibiotics in hospitals?

A: We do sophisticated procedures where we knock out patients’ immune systems with chemotherapy or prior to transplants. That makes people more susceptible to infection, so we use antibiotics more frequently.

Q: And that means more resistance?

A: Yes. Vancomycin-resistant enterococci were first seen in the late 1980s. They spread rapidly from the mid-Atlantic region and are now a major problem in hospitals across the country.

   And it’s not just enterococci. We’re seeing increasing levels of resistance in all of the major pathogens: Staphylococci, Pseudomonas, E. coli, Klebsiella. There have been steady increases in both the percentage of bacteria that are resistant to antibiotics and the number of antibiotics to which they are resistant.

Q: What’s causing that increase?

A: The genes for resistance to different antibiotics are getting linked together in bacteria. Unlike humans, bacteria trade genes with each other. So the capacity to resist several antibiotics can be linked together and transferred to other bacteria that may never have been exposed to the antibiotics. The combination of resistance genes in bacteria is becoming a major problem.

Q: And resistance is spreading beyond hospitals?

A: Right. These days, people are being sent home from the hospital more quickly. So many of the bugs that we assumed were confined to the hospital are now spreading into the community. For example, there are increasing reports of methicillin-resistant Staphylococcus aureus, which is a fairly nasty bug that used to be found only in hospitals. Now it’s beginning to cause problems everywhere.


Q: Does some antibiotic resistance start in the doctor’s office?

A: Yes. The best example is pneumococci, which causes pneumococcal pneumonia. When I was a medical student, one of the absolutes was that pneumococci were always killed by penicillin. That’s not true any more.

   Over the last decade, we have watched the rates of resistance to penicillin in pneumococci skyrocket. Depending on where we survey, we’re talking 20 to 30 percent of pneumococci that show some level of resistance to penicillin. In parts of Europe, it’s over 50 percent.

   Interestingly enough, the rates of resistance are highest in wealthy suburban areas. One of the main causes seems to be the antibiotics used by pediatricians to treat kids with ear infections. Pneumococci are a major cause of ear infections and penicillin is usually the treatment.

   So if you’re a good parent and always take your kid to the doctor, your child is much more likely to have a resistant pneumococci because the child received so many antibiotics. Low-income kids, who don’t go to doctors that often, are less likely to have resistant pneumococci.

Q: Are antibiotics often unnecessary?

A: Yes. When people with an upper respiratory infection go to the doctor, they often expect to walk out of the office with an antibiotic. In reality, most colds, sore throats, flus, and general I-don’t-feel-good low-grade fevers that everybody gets during the winter are caused by viruses, which are not killed by antibiotics. All antibiotics do is help bacteria become resistant to them.

   When it comes to bacterial infections, there are certain groups of people— the elderly, babies, people who have weakened immune systems— who need antibiotics. But for most normal healthy adults and children, antibiotics are vastly overused.

Q: Does bronchitis require antibiotics?

A: Not always. Physicians sometimes use bronchitis as a “wastebasket” diagnosis. They’re not sure what’s going on and the patient is coughing, so they’ll say, “We’ll just put you on antibiotics.” Many of those infections are caused by viruses, and won’t be helped by antibiotics.

Q: Why do doctors prescribe antibiotics unnecessarily?

A: Doctors feel pressure because they’re afraid they’ll lose their patients. Pediatricians say, “Parents will think I’m a lousy doctor because they took off time from work, they pulled their child out of day care, and I looked at the kid and said, ‘Yup, he’s got a cold. Bye.’”

   And patients feel like, “Why did I spend all this time going to the doctor when I didn’t get anything?” There’s a sense that if I don’t walk out of the office with a prescription, I got shortchanged. That mindset has got to change.

   The most important message for consumers is to be aware that most of the time you see a doctor for an upper respiratory infection like a cold or sore throat, you don’t need an antibiotic. Rather than say, “Why don’t you give me an antibiotic?” the question consumers should ask is, “Are you absolutely sure that I need this antibiotic?” Frequently, the answer will be, “I’m not sure you really need it.” And in those circumstances, you shouldn’t take it.

Q: But people say: “I took antibiotics and I got better.”

A: Of course. But in most cases they would also have gotten better without them. The danger is that if you take antibiotics for an upper respiratory infection, for example, you may well develop resistant pneumococci. It’s sitting in the back of your throat, so the next time you—or someone you infected with those bacteria— really need antibiotics, it may be more difficult to treat the infection.

   Antibiotics are not innocuous. The problem is that the consequences don’t happen immediately.

Q: What needs to change?

A: We need to vaccinate more people, especially seniors, against the flu and pneumonia, so that there are fewer situations in which questions about antibiotic use arise. And we need new antibiotics. But it takes a long time for a new drug to make it all the way through testing, development, licensing, etc. So we also need to minimize the unnecessary use of drugs—in both animals and people— to preserve what we have as long as possible. Virtually any antibiotic will ultimately develop resistance. We can no longer assume that an antibiotic will work forever. There is no forever.

Infectious-disease expert Glenn Morris is a physician and epidemiologist at the University of Maryland School of Medicine in Baltimore. Morris, a member of Nutrition Action Healthletter’s Scientific Advisory Board, spoke to NAH’s Bonnie Liebman.


While it’s always best to ask your doctor if antibiotics are necessary for you or your child, here are some basic guidelines to keep in mind:

 Don’t expect or demand antibiotics from your doctor. Let your physician determine whether or not you can fight off an infection by yourself.

 If you’re taking an antibiotic, take the full course of treatment. If you stop taking antibiotics early—even if you feel better—the bacteria that are still alive can breed resistance and possibly rekindle an infection.

 Don’t save antibiotics for later use or share them with others. A doctor should evaluate each person each time he or she is sick.

 Antibiotics may cause mild to severe side effects such as nausea, diarrhea, and allergic reactions. They also may kill naturally occurring bacteria that protect your body from yeast infections. If you experience any of the above symptoms, call your doctor.

 Sore throats, colds, and flu are caused by viruses, not bacteria, so taking antibiotics won’t help. One exception is strep throat, which is caused by bacteria. A throat culture can determine what you have and whether it’s best treated with antibiotics.

 Coughs and bronchitis are almost always caused by viruses. Exception: if your symptoms last for more than two weeks, or if you have a lung condition, it could be caused by bacteria.

 Ear infections come in several types. If your doctor doesn’t recommend an antibiotic, don’t ask for one.

 Sinus infections may be caused by bacteria or viruses. Antibiotics should only be used for severe infections, or ones that last more than two weeks, since those are more likely to be caused by bacteria.

Sources: Adapted from information provided by the American Academy of Family Physicians, the American Academy of Pediatrics, the Alliance for the Prudent Use of Antibiotics, and the Centers for Disease Control and Prevention.


For more information

about what can be done to prevent antibiotic-resistance, visit CSPI’s Web site ( If you know of someone who was made seriously ill by antibiotic-resistant bacteria, please write to:

CSPI–Resistance, Suite 300,
1875 Connecticut Ave. N.W.,
Washington, D.C. 20009.


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