FRIDAY, March 23, 2018 (HealthDay News) -- More than one-quarter of non-antibiotic medicines inhibit the growth of bacteria in the human gut and may contribute to antibiotic resistance, new research suggests.
Many species of bacteria live in the human gut -- collectively known as the gut microbiome -- and antibiotics can affect the balance. But the effect of non-antibiotic medicines on gut bacteria had been unclear.
Researchers at the European Molecular Biology Laboratory, in Germany, tested about 1,000 medicines on 40 species of gut bacteria. Of 923 non-antibiotics tested, 250 affected the growth of at least one of species of gut bacteria.
"The number of unrelated drugs that hit gut microbes as collateral damage was surprising. Especially since we show that the actual number is likely to be even higher," study co-author Peer Bork said in a laboratory news release.
Bork noted that the shift in gut bacteria makeup contributes to drug side effects, but also might be part of the drugs' beneficial action.
Co-author Kiran Patil pointed out that scientists have much more to learn.
"We don't know yet how most of these drugs target microbes, how these effects manifest in the human host, and what the clinical outcomes are," Patil said. "We need to carefully study these relationships, as this knowledge could dramatically improve our understanding and the efficacy of existing drugs."
The findings open up the worrisome possibility that non-antibiotic drugs may contribute to antibiotic resistance, another co-author added.
"This is scary, considering that we take many non-antibiotic drugs in our life, often for long periods," said co-author Nassos Typas. "Still, not all drugs will impact gut bacteria and not all resistance will be common. In some cases, resistance to specific non-antibiotics will trigger sensitivity to specific antibiotics, opening paths for designing optimal drug combinations."
The researchers said their study is the first to investigate direct interactions between marketed drugs of all kinds and individual gut bacteria.
This line of research could also lead to personalized drug therapies, according to study co-author Georg Zeller.
"We all carry different bacterial species -- besides several common ones -- and on top of that, we carry different individuals of the same species called strains. These strains can have very different functionalities, including the response to drugs," Zeller said.
"Therefore," he added, "many drug-microbe interactions are likely to be individual, opening paths for personalized drug therapies aimed at the individual gut microbiome."
The findings were published March 19 in the journal Nature.
The U.S. National Institutes of Health has more on gut bacteria.