Doctors warn against excess use of germfighting drugs
OVERDOSING ON ANTI BIOTICS
Doctors warn against excess use of germfighting drugs
The pressure tactics used by patients at Dr. Warren Mclsaac’s family practice in Toronto are both varied and subtle. “Sometimes, people will just sit there— there’s a sense of disappointment,” Mclsaac says, describing what happens when he tells patients they do not need antibiotics. “Other people say things like, ‘Look, every time I get a cold, it goes right to my chest if I don’t get antibiotics.’ ” Even though Mclsaac tries to explain to them that cold viruses are immune to antibiotics—and that the overuse of such drugs can make it harder to fight future infections—he admits he sometimes prescribes the drug anyway. “There are times I’ve given in when people are especially demanding,” he says. “You know that the only reason they’re at the doctor is because they feel you can give them antibiotics.”
It may all seem harmless enough, but experts warn that the unnecessary use of antibiotics is contributing to what may soon develop into a public health emergency. Around the world, bacteria that cause dysentery, gonorrhea and tuberculosis are becoming increasingly resistant to the antibiotic drugs most commonly used to treat them. And in Canada, infectious disease specialists are now identifying resistant germs with alarming regularity. “It’s sort of an arms race,” says Julian Davies, head of microbiology and immunology at the University of British Columbia in Vancouver. “And by using antibiotics the way we do, we’re providing microbes with the arms.”
As an illustration, researchers point to what is happening with Streptococcus pneumoniae, one of the most common causes of bacterial infection and the bug responsible for most ear infections, pneumonia and meningitis. Most strep infections are easily treated with a simple dose of penicillin. But Dr. Andrew Simor, head of microbiology at Sunnybrook Health Science Centre in Toronto, says the germ is becoming resistant to penicillin at a frightening rate. Some 13 per cent of strep germs can no longer be treated with normal doses of penicillin—up from 1.5 per cent in 1993. As many as half of those are also resistant to other common antibiotics such as tetracycline and erythromycin, forcing doctors to choose medicine that is more expensive and that causes more side-effects. “This is an important bug,” says Simor. “And because of this resistance, it is becoming extremely difficult to treat”
Doctors are also worried about a recent outbreak at The Toronto Hospital of a potentially dangerous strain of enterococcus—a bacteria commonly found in the bowel that if it migrates to other parts of the body, can cause blood, bladder and kidney infections in people who are already ill. Identified in 36 kidney patients during routine screening, the germ caused only one person to become seriously ill—requiring the use of experimental drugs.
But Dr. John Conly, the centre’s director of infection control, fears that if it turns up again it could pass its resistant DNA to a strain of staphylococcus bacteria—a common cause of wound infection, toxic shock syndrome and food poisoning—for which only one antibiotic, vancomycin, is effective. If that happens, says Conly, the antibiotic could be rendered ineffective, making some staph infections untreatable:
“We would be back in the era of acute infectious diseases causing serious mortality in our population.”
Unfortunately, bacteria have an extraordinary ability to adapt to their environment. Germs can thwart antibiotics with the use of genetic material called plasmids, which remodel the germs’ DNA Successfully altered bacteria can change their outer walls or rearrange their internal makeup to stop antibiotics from doing their job.
They can even produce enzymes that annihilate the drugs meant to destroy them. Bacteria are also among the most promiscuous of organisms, sharing their resistant DNA with a wide variety of other bacteria. And they procreate at a breakneck pace. Bacteria can divide every 20 minutes and, in ideal conditions, can produce a new colony of more than 250,000 cells within six hours.
Bacteria’s propensity for survival became obvious in the early 1940s, when staph infection developed penicillin resistance within a few years of the drug’s introduction. More than 100 new antibiotics have been developed since, but bacteria have generally found a way to outsmart them. One problem confronting doctors is that there has been no new class of antibiotics produced for at least 10 years—in part, because drug companies underestimated the need for new forms of treatment. But even if new approaches are found, experts say bacteria would eventually circumvent them. “Many of us feel we are on a treadmill,” says ’ Dr. Lindsay Nicolle, former director of the infection control unit at I Winnipeg’s Health Sciences Centre. “The bugs are a lot smarter than i we are, and are always two steps ahead of us.” j> Every exposure to an antibiotic—even if the drug is being properly Î used—gives bacteria another chance to utilize their evolutionary skill. I A steady increase in the use of such drugs has given the germs an even ; greater hand in their fight to survive. “The more you use an antibiotic,
: the more resistance you have,” notes Dr. Stuart Levy, co-founder of the \ Boston-based Alliance for the Prudent Use of Antibiotics. According to I market analyst IMS Canada, pharmacists dispensed 24.3 million pre: scriptions for oral antibiotics in the 12 months ending Oct. 31,1995—a
Bacteria will always find ways of resisting antibiotics. Experts say, however, that the problem can be kept to a minimum with proper drug use. Some factors to keep in mind:
• Colds, flu and up to 90 per cent of sore throats are caused by viruses and do not respond to antibiotics. Dr. George Miller, a Kitchener, Ont., family physician and a member of the Canadian Medical Association’s health-care committee, says antibiotics should never be taken to treat viral infections; such use promotes resistance among bacteria that reside in the body.
• So-called broad-spectrum antibiotics, designed to wipe out several types of bacteria at once, are often prescribed when a doctor has not made a clear diagnosis. Miller recommends waiting a day or two for test results so the doctor can prescribe the most specific antibiotic possible.
• Patients with bacterial infections often feel better and stop taking antibiotics after a few days. Failure to complete the full course of treatment, however, can give the hardiest germs a chance to develop resistance.
• Using antibiotic pills left over from a previous infection or passed on by a friend does more harm than good. The practice gives germs that live in the body an extra chance to adapt. It can also make diagnosis of the illness more difficult.
10-per-cent increase over the same period in 1991 and a number surpassed only by prescriptions for cardiovascular drugs. Hospital use of broad-spectrum antibiotics such as vancomycin—commonly used to treat infections after surgery—has also grown by as much as 30 per cent.
The increase is at least partly justified: patients who have undergone organ transplants, for example, need more powerful antimicrobials to keep infections at bay. But in many other instances, researchers say the use of antibiotics is unnecessary, a result either of unrealistic patient demands or hurried diagnoses. According to a recent study in The Journal of the American Medical Association, as many as half of all antibiotic prescriptions are not needed. “It’s almost a generational phenomenon that we want the quick fix in society, and antibiotics fall into that category,” says Conly.
Mclsaac, who is studying antibiotic use at the Institute for Clinical Evaluative Sciences in Toronto, says patients often expect to get the drugs even if they have a cold or flu, which are caused by viruses and cannot be treated with anything but fluids, rest and painkillers. Just as often, doctors have difficulty making an accurate visual diagnosis of an illness such as strep throat or an ear infection; patients, meanwhile, are unwilling to wait for test results. As a result, he says, physicians prescribe antimicrobials for up to a third of patients with a sore throat—twice the number who actually need it
Children with ear infections also appear to be receiving too many drugs, adds Dr. Ronald Gold, an infectious disease specialist at Toronto’s Hospital for Sick Children. Ear infections are routinely treated with antibiotics. Recent studies show, however, that as many as 60 per cent get better just as quickly without treatment. The problem, says Gold, is that doctors lack “a simple way of identifying which children don’t need antibiotics. We’re stuck.”
Many experts also believe the rampant use of antibiotics in animals grown for human consumption has contributed to germ resistance. Such drugs are commonly fed to animals so their energy can be directed towards quick growth rather than fighting infections. There is no evidence that animal germs that have developed resistance to antibiotics pose any threat to humans. The resistant DNA, however, can be transferred to human bacteria, resulting in an even greater pool of bugs for which there is no easy treatment
Given science’s inability to come up with drugs that can outsmart bacteria, researchers are working to develop new vaccines that could prevent the most common germs from causing infections in the first place. They have had recent success with hemofluous B influenza, a highly resistant childhood bacteria that in the past three years has been all but eliminated in Canada thanks to a vaccine routinely injected in two-month-old babies. A vaccine for Streptococcus pneumoniae has also shown promising results. But as Sunnybrook’s Simor points out, even vaccines are of limited value since they are only effective against 65 per cent of the targeted germs. For most people, the best advice is to treat antibiotics with equal doses of respect and sober second thought.
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