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Antibiotics and Asthma

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Taking antibiotics early in life can lead to asthma, according to a study in mice.


Transcript

Antibiotics and asthma. I’m Bob Hirshon and this is Science Update.

Kids who take antibiotics before the age of one are more likely to develop asthma. A new study in mice at the University of British Columbia suggests that’s no coincidence. Microbiologist Brett Finlay and his colleagues gave the mice one of two antibiotics: vancomycin or streptomycin.

Finlay:
And what we found is that vancomycin, but not streptomycin, caused a profound increase in the amount of asthma in these animals. And what also was really interesting is that it only worked if you gave the antibiotics to these mice when they’re very young, basically right after birth.

Finlay says that the two drugs kill different types of gut bacteria, some of which may protect us from asthma as the immune system develops. It’s part of a growing awareness that the bacteria in our bodies play a key role in keeping us healthy. I’m Bob Hirshon for AAAS, the Science Society.


Making Sense of the Research

Asthma and allergies have been steadily increasing in developed countries, and better diagnoses alone can't explain it. For instance, life-threatening peanut allergies are now so common that many schools have taken peanuts out of their cafeteria menus, and some schools even ban it in food brought from home. But just a few decades ago, allergies like that were much rarer. 

Yet in developing countries, asthma and allergies haven't been increasing like this. In fact, they're still relatively unheard of. Why? Scientists don't know for sure, but one popular explanation is called the “hygiene hypothesis.” Simply put, it states that life in modern, industrialized countries has become so sanitized that our immune systems don't have enough germs to fight—so instead, they attack harmless substances, like peanuts or pollen. 

Originally, the hygiene hypothesis focused on the effects of our surroundings—like living in solidly built homes scrubbed down with antiseptics, and consuming clean, parasite-free food and water. However, more and more research indicates that our body's internal environment may be just as important, if not more. All human beings are colonized with trillions of bacteria, most of which are harmless or even beneficial. However, since the mid-20th century, we've been taking more and more antibiotics to treat various illnesses. Most of these antibiotics kill far more types of bacteria than the ones causing the illness. As a result, we're greatly reducing the bacterial populations of our bodies on a regular basis, and probably wiping out countless species for good.

This study looked at this issue by testing the effects of two common antibiotics on asthma in mice. They found that one of the two antibiotics they chose did lead to an increase in asthma—but only if the antibiotic was given early in the mouse's life. That suggests that infants and young children may be especially vulnerable to the effects of antibiotics, perhaps because their native bacterial populations are still developing.

More work needs to be done to confirm this hypothesis. This particular study looked at the effects of only two antibiotics; many more are used in contemporary medicine. However, human studies do show that children who took antibiotics before age two are more likely to develop asthma later in life. So that's consistent with the findings from this mouse study. And of course, even if it's true that antibiotics contribute to asthma and allergies, doctors will still have to weigh the costs and benefits of these medicines. After all, antibiotics have saved countless lives, and abandoning them altogether wouldn't be beneficial. We may just need to be more judicious about using them, or develop better drugs that target only the source of the sickness.

Now try and answer these questions:

  1. What is the hygiene hypothesis? How does it relate to asthma and allergies?
  2. It was already known that children who took antibiotics early in life were more likely to develop asthma later on. What's the benefit, then, of doing this mouse study?
  3. What choices will we have to make about using antibiotics in the future? 
You may want to check out the April 6, 2012, Science Update Podcast to hear further information about this Science Update and the other programs for that week. This podcast's topics include: A promising new drug that could work on all types of cancer, new evidence linking antibiotic use to asthma, a test that takes the guesswork out of choosing the right antibiotic when one is needed, and how your biological clock affects your health.


The Science Update Anti-Asthma Bug describes an earlier study linking stomach bacteria to asthma. 

The Science Update M.S. And Gut Bacteria delves into a possible link between some kinds of gut bacteria and multiple sclerosis, a nervous system disease.

Another Science Update, Human Microbial Diversity, focuses on the rich variety of bacteria that live inside us. 

The booklet Asthma and Allergies: The Science Inside explains the basics of these respiratory conditions, their relationship to each other, prevention, treatments, and more.


Going Further


For Educators

The Science Update lesson Anti-Asthma Bug describes an earlier study linking stomach bacteria to asthma. 

The Science Update lesson M.S. And Gut Bacteria delves into a possible link between some kinds of gut bacteria and multiple sclerosis, a nervous system disease.

Another Science Update lesson, Human Microbial Diversity, focuses on the rich variety of bacteria that live inside us. 

The booklet Asthma and Allergies: The Science Inside explains the basics of these respiratory conditions, their relationship to each other, prevention, treatments, and more.


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