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Antibiotic Overuse May Be Bad for Body's Good Bacteria

Some Researchers Believe Changes in Helpful Bacteria May Be Contributing to Obesity, Asthma

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“That works so well that it accounts for more than half of antibiotic use in the United States,” Blaser says. “Since it works in chicken, turkeys, cows, and sheep, I presumed it would work in mice, and it does.”

Antibiotics, he thinks, may also be contributing to obesity in humans, though Blaser says no one yet understands how.

Beyond obesity, he says studies have shown that a child’s risk for inflammatory bowel disease increases with the number of courses of antibiotics taken.

He also says antibiotics may be a factor behind the unexplained rises in allergies, asthma, and type 1 diabetes in children.

But his commentary in Nature does not prove that. Blaser's paper is his opinion, not a new study.

Other research, directed by the Human Microbiome Project, which aims to catalogue and understand the microorganisms that live in the body, has suggested that a bacterial environment that’s out of balance in the stomach and esophagus may contribute to cancer.

An out-of-balance bacterial environment in the digestive system may lead to inflammation, and inflammation may cause changes in cells that lead to cancer, Proctor says.

Protecting Good Bacteria

Though such research is in its early stages, some experts say Blaser’s call to action is on target.

“There’s really only a limited number of studies that have been done on this so far, but I think we’re going to see more because I think it’s going to be a big deal for us to understand this,” says George Weinstock, PhD, a professor at the Genome Institute at Washington University in St. Louis.

But "the evidence is all circumstantial," Alexander Khoruts, MD, associate professor of medicine at the University of Minnesota, tells WebMD in an email. He says there is an "urgent need" to see if overuse of antibiotics are causing the problems Blaser describes, and that there is "little doubt that antibiotics have been overused in clinical and veterinary medicine, and farming practices." But Khoruts says he is "less than convinced that we have enough data to revise guidelines for solid indications for antibiotic usage."

Because studies have already shown that antibiotic overuse is contributing to the problem of drug resistance, Blaser believes it’s not rash to act in advance of more definitive science.

“We all know that there’s antibiotic overuse early in life, and I’m giving us yet another reason why we have to control it,” he says.

Among measures he’d like to see in place are better diagnostic tests that would help doctors more quickly pinpoint the cause of an infection.

Blaser says it’s critical to swap the widely used broad-spectrum antibiotics, which can kill many different kinds of bacteria, for agents that more narrowly target the bug that’s causing the disease.

And he says effective probiotics are needed to replace lost good bacteria.


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