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Science Matters

Misuse of Antibiotics

David Suzuki

More than a quarter-century ago, | did a television program that discussed the hazards of misusing antibiotics, including using antibiotics as growth-promoters in livestock. Today, this practice continues in much of the world even though it has been implicated in the rise of antibiotic resistance, which can make some of our most powerful drugs useless.

Antibiotics are an extremely important tool in modern med- icine. In the 1940s | came down with pneumonia and was close to death when a doctor injected me with penicillin. It was like a miracle—the next day | was up and out of bed. Antibiotics have saved countless lives by repelling bacteria. But bacteria evolve quickly and can become resistant to our drugs. So we create new drugs. Then the bacteria evolve again. Some have now evolved to the point that they are resistant to all of our drugs—they have become “superbugs.”

In July, the most recent superbug, a type of Staphyloccocus aureus, was found in an American patient suffering from a leg ulcer. S aureus is actually a common bacteria often found in healthy people, but it can sometimes lead to severe infections. In this case, doctors tried several different antibiotics, but to no avail. Their last resort was a powerful antibiotic called van- comycin. To their surprise, it had no effect. An older drug even- tually managed to stop the infection, but the patient was lucky to survive.

Although doctors have been expecting this to happen even- tually, finding such a resistant strain of a common bacteria was disturbing. Fifteen years ago, doctors discovered a van- comycin-resistant strain of the common stomach bacterium Enterococcus, and it now plagues the intensive-care sections of hospitals. S aureus has the potential to be a much bigger

Must be Curtailed

like Salmonella. The US Food and Drug Administration esti- mates that every year up to 10,000 Americans develop antibiotic-resistant infections from eating chicken containing such bacteria. Second, resistant bacteria found in food ani- mals can transfer resistance to normally harmless bacteria in humans through physical contact. These common bacteria are persistent and may spread from person to person. Occasionally, they can cause infections, and if the bacteria are resistant to antibiotics, the infection may prove difficult to treat.

Recently, a group of US scientists developed a mathemat- ical model to examine how feeding antibiotics to livestock can lead to resistance. Their findings, published in the Proceedings of the National Academy of Sciences, indicate that giving animals massive doses of antibiotics that are also used for humans reduces the useful life span of the drug by about 30 per cent.

Importantly, they also conclude that allowing antibiotics to be used in agriculture until resistant strains are discovered will not likely be effective “because once antibiotic-resistant bac- teria are detected, much of the damage has been done?’ They recommend that if antibiotics are to be used in agriculture as growth promoters at all, then only those that have ceased to be helpful to humans should be used.

Researchers are hard at work developing new antibiotics. Recent breakthroughs, including the sequencing of the genome of an important bacterium and the discovery of a key to antibiotic resistance in one of the superbugs, are promising advancements. But unless we stop the rampant misuse of antibiotics, the effectiveness of new drugs will continue to be compromised.

To discuss this topic with others, visit the discussion forum at www.davidsuzuki.org.

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