Antibiotics and side effects : unthinkable consequences

Unwanted impact of antibiotics broader, more complex than previously known

CORVALLIS, Ore. – Researchers at Oregon State University have discovered that antibiotics have an impact on the microorganisms that live in an animal’s gut that’s more broad and complex than previously known.

The findings help to better explain some of the damage these medications can do, and set the stage for new ways to study and offset those impacts.

The work was published online in the journal Gut, in research supported by Oregon State University, the Medical Research Foundation of Oregon and the National Institutes of Health.

Researchers have known for some time that antibiotics can have unwanted side effects, especially in disrupting the natural and beneficial microbiota of the gastrointestinal system. But the new study helps explain in much more detail why that is happening, and also suggests that powerful, long-term antibiotic use can have even more far-reaching effects.

Scientists now suspect that antibiotic use, and especially overuse, can have unwanted effects on everything from the immune system to glucose metabolism, food absorption, obesity, stress and behavior.

The issues are rising in importance, since 40 percent of all adults and 70 percent of all children take one or more antibiotics every year, not to mention their use in billions of food animals. Although when used properly antibiotics can help treat life-threatening bacterial infections, more than 10 percent of people who receive the medications can suffer from adverse side effects.

“Just in the past decade a whole new universe has opened up about the far-reaching effects of antibiotic use, and now we’re exploring it,” said Andrey Morgun, an assistant professor in the OSU College of Pharmacy. “The study of microbiota is just exploding. Nothing we find would surprise me at this point.”

This research used a “cocktail” of four antibiotics frequently given to laboratory animals, and studied the impacts.

“Prior to this most people thought antibiotics only depleted microbiota and diminished several important immune functions that take place in the gut,” Morgun said. “Actually that’s only about one-third of the picture. They also kill intestinal epithelium. Destruction of the intestinal epithelium is important because this is the site of nutrient absorption, part of our immune system and it has other biological functions that play a role in human health.”