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Probiotics are living bacteria taken to improve digestive health, but a study on mice suggests that they evolve in the intestine and can become harmful over time.
Researchers at the University of Washington School of Medicine studied a strain of E. coli bacterium sold as an anti-diarrheal probiotic in Europe. After a few weeks in the intestines of mice, the bacteria could damage the protective lining of the intestine, linked to irritable bowel syndrome.
For the study, they used mice with four types of intestinal microbiomes: one without any pre-existing bacteria; one with a limited set of bacteria, characteristic of an unhealthy gut; a normal microbiome; and a normal microbiome after antibiotic treatment. Each mouse received the probiotic E. coli Nissle (EcN) and fed a different diet consisting of a mouse food, which mimics the natural diet of the mouse; a diet rich in fat and low in fiber similar to the Western diet; or a western diet with fiber. After five weeks, the researchers took the bacteria from the gut of the mice and badyzed the DNA of the microbes.
The diet of mice and the composition of their intestinal bacterial community have influenced the evolution and modalities of evolution of the probiotic.
"In transit, EcN accumulates genetic mutations that modulate carbohydrate utilization, stress response, and adhesion to improve fitness, while prior antibiotic exposure reveals resistance acquisition." ", says the study.
Aura Ferreiro, graduate student and first author, said, "In a healthy and diverse context, we have not captured much adaptation, perhaps because it is the context that Nissle is used to.
"But you have to remember that very often, we do not use probiotics in people with a healthy microbiome. We would use them in sick people who have a poorly diversified and unhealthy microbiome. And this seems to be the case when the probiotic is most likely to evolve. "
The findings suggest that a probiotic relieving one person could become ineffective or even harmful in another.
"If we use living things as drugs, we have to recognize that they're going to adapt, which means that what you put in your body is not necessarily what you're going to have even a few hours later, "Gautam Dantas, senior author and professor of pathology and immunology, molecular microbiology and biomedical engineering. "No microbe is immune to evolution. This is not a reason not to develop probiotic-based therapies, but it's a reason to make sure we understand how they change and under what conditions. "
Probiotics are being developed for the treatment of serious diseases, such as inflammatory bowel disease and phenylketonuria (PKU), a metabolic disease that causes neurological damage. The findings of the study could not only serve to better understand the safety of probiotics, but also potentially personalize probiotic-based medicine in the future.
The search was published in Cell Host and Microbe.
