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by Katya Frazier
Graduate student in the Committee on Molecular Metabolism and Nutrition

If you’ve had strep throat or an ear infection, you likely have deep respect for antibiotics. They powerfully fight off bacteria—by damaging their DNA, disarming their protein-making machinery, or causing their cell walls to explode.

But what happens if antibiotics inadvertently target the “good” bacteria in our bodies? These are the micro-organisms that help us digest our food, make our vitamins, keep our skin moisturized, tune our immune system, and so much more.

For over a decade, scientists and physicians have noticed a connection between early use of antibiotics and inflammatory bowel diseases (IBD)—chronic, painful gastrointestinal conditions that are growing in incidence at an alarming rate. IBD, the umbrella term for Crohn’s disease and ulcerative colitis, affects over 1.5 million in the U.S. alone. As many people can attest, there are few effective therapies that provide lasting relief.

Recently, Eugene Chang, MD, and his team at the University of Chicago published a study aiming to understand the connection between antibiotics and IBD development. In this study, Jun Miyoshi, MD, PhD, and Alexandria Bobe, PhD, treated pregnant, genetically susceptible mice with antibiotics and then observed both the mothers and their new pups over time.

Mouse pups whose mothers were treated with antibiotics did, indeed, tend to develop IBD-like symptoms, but the evidence showed a more complicated story. Since the antibiotics were not transmitted from mother to pups, Miyoshi and Bobe could determine that it wasn’t the antibiotics themselves that triggered the IBD symptoms. Instead, the antibiotics disrupted the bacterial community in the mothers, and this unbalanced microbiota (dysbiosis) was transferred to the pups during pregnancy, delivery, and nursing. The gut dysbiosis skewed the pups’ immune system, priming them for inflammation and increased development of IBD-like symptoms, as compared to non-treated mice.

Interestingly, the mothers of these pups, as well as other adult mice given the same antibiotic exposure, tended not to develop symptoms, which include weight loss and diarrhea. It was as if their immune systems, which were fully mature before they were exposed to the antibiotics, kept them from developing symptoms—even though they were genetically primed.

These experiments seem to indicate a direct, causal link between gut dysbiosis—an imbalance of bacteria in the gut, which can be caused by antibiotic use—and later development of IBD, especially in those with both immature immune systems and a background of genetic susceptibility. This is not to say that we should stop using antibiotics, as they can be crucial, life-saving treatments. What this study does show is the powerful, complex effects of gut bacteria during early life on our health. And this may be true not just for IBD, but other inflammatory diseases as well, from allergies to certain types of arthritis.

This research and others suggest promising new avenues to improve health. What if the balance of bacteria in our gut could be used as a biomarker to diagnose or even predict IBD? And what if we could find a way to reset the microbiota in the gut and tame the inflammation that results in IBD?

Diving into the complex mechanisms of the gut microbiome

Although research has revealed so much, the mechanisms by which the microbes in our bodies affect disease are still cloudy. Microbial communities in the gut are not only complex, but thrive only in an air-free environment, which makes them particularly difficult to study. But the more we discover about the dynamics of the microbiome—in both healthy and sick individuals—the better chance we have to turn the dial towards health. The Duchossois Family Institute was established to advance these discoveries.

But that is only part of the Duchossois Family Institute mission. It will also drive translation of bench research on the microbiome more efficiently into the clinic and back again to the lab. We need to better understand how our current lifestyles and treatments affect the bacteria living within us, so we can help countless other people achieve a lifetime of vigor and good health.

Photo by Seweryn Olkowicz/WIKIMEDIA COMMONS