Antibiotics may have long-lasting effects on gut flora

Repeated antibiotic treatments can alter the gut’s bacterial flora and weaken its protective mucus barrier, according to new research from the Universities of Umeå and Tartu.

The study, published in the scientific journal Gut Microbes, examined patients who had undergone at least five courses of antibiotics. The researchers analyzed stool samples from these patients, where it had been at least six months since their last antibiotic treatment. The results were then compared with samples from people who had not taken antibiotics for 10 years.

The analyses showed significant changes in the composition of gut bacteria.

– These results indicate that repeated antibiotic use has a lasting effect on gut bacteria composition that can persist at least months after the last treatment, said Kertu-Liis Krigul, a PhD student at the University of Tartu, in a press release.

The researchers transplanted the gut flora from these patients into mice to analyze the function of the mucus barrier. In mice that received bacteria from patients with repeated courses of antibiotics, the mucus layer was damaged and mucus production decreased, making it more permeable and allowing bacteria to get closer to the intestinal wall.

A separate study, conducted in international collaboration and published in Science Advances, showed that the antibiotic vancomycin directly disrupted the mucus barrier. When the antibiotic was given to both normal and “germ-free” mice, mucus production in the gut was disrupted within minutes.

– Together, these two studies suggest that antibiotics can damage the mucus layer through at least two independent mechanisms, and that they may have long-lasting effects through an altered gut bacteria. This further supports the notion that antibiotics should be administered in a responsible manner, says Björn Schröder, Associate Professor of Infection Biology at the Department of Molecular Biology at Umeå University.