In recent decades, the incidence of non-infectious diseases, such as asthma, allergies, diabetes, and others has risen dramatically—a change Martin Blaser of New York University School of Medicine suspects might be due to the increased use of antibiotics, which not only kill pathogenic bacteria, but our bodies’ “friendly flora” as well. In a comment in this week’s Nature, Blaser laid out his approach to understanding the impact of antibiotics on microbiota in humans. The Scientist spoke with Blaser about his travels to the depths of our guts and the Peruvian Amazon to find the answers.
The Scientist: What is the role of friendly flora in our bodies?
Martin Blaser: Animals have had colonizing bacteria ever since we were animals, let’s say a billion years. There’s evidence that as we’ve evolved, so have our friendly flora. There’s lot of evidence that they’re doing beneficial roles for us, including metabolic roles and helping us fight invading organisms. And my hypothesis is that in the 20th century things started to change, and this is due in part by the use of antibiotics.
TS: What is the evidence that our friendly flora never recover from antibiotics?
MB: There is epidemiological evidence on Helicobacter pylori, which has been the dominant ancient organism of the human stomach since time immemorial, that it is disappearing. Helicobacter is becoming extinct. This is what has got me thinking in this area, because if Helicobacter can become extinct, so can other organisms.
TS: What evidence is there that killing friendly flora might be linked to non-infectious diseases like type I diabetes and inflammatory bowel disease?
MB: In Danish kids, the more courses of antibiotics they get, the more likely they are to get IBD. There are studies from Canada showing the same thing for asthma. More courses of antibiotics, more asthma.
Type 1 diabetes has been going up pretty dramatically. It’s basically doubled. So I’m postulating that there might be a role [for] changing microbiota as well.
TS: How can antibiotic use be limited? For instance, it’s standard policy to give antibiotics to babies when they’re born.
MB: This is an example of how, for very good reasons, we’re exposing mothers and babies to antibiotics based on the idea that there’s no cost. But what if there is a cost?
About 30 percent of women carry group b strep in their vaginas. And the policy is that all get antibiotics to prevent transmission to their babies. But only one out of 200 babies will get ill. So we’re treating 200 women to save one baby from getting sick. In terms of policy, we have to figure out, to a much better degree, how to find that one in 200 babies.
TS: What current research projects do you have in place?
MB: I mentioned that we’re conducting studies in the Amazon with Maria Gloria Dominguez Bello, [a professor at the University of Puerto Rico]. We’ve been working together for a number of years to understand the microbiota of people who have not been much affected by modern society. We recently went on an expedition in Peru with Oralee Branch [from NYU’s Langone Medical Center] to study people in the Peruvian Amazon who’ve had little contact with antibiotics because we want to compare their microbiota with our modern ones.
Part of our study is to culture some of these organisms and put them in the freezer. It’s archival. We’re just really at the beginning of this, because microbiota is very complex. It might not be the same for everybody. We don’t know.
TS: Is there a way to replace friendly flora once it’s been wiped out?
MB: Now we’re moving into a futuristic time frame, but I believe that doctors of the future are going to be doing that. When babies are born they’re going to figure out what’s missing, and just as a child gets their immunizations, they’ll get a dose of the missing bacteria so that they can get the early life benefits just as all their forebears have.
TS: Are there any policies that can be effective now?
MB: It’s already a broad policy to decrease antibiotic overuse. It’s just that everybody wants somebody else to decrease it, somebody else’s kids. If we can decrease antibiotic overuse, then we can slow down what’s happening. But we can’t turn it around. We need to invest in narrower spectrum antibiotics. We need to invest in better diagnostics, so doctors know which organism is involved.
M. Blaser, “Stop the killing of beneficial bacteria,” Nature, 476: 393-4, 2011.