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Can probiotics have a negative impact on bacteria in the intestine?
It has been known for a long time about so-called probiotics that they have a positive influence on the bacteria in our intestines. However, researchers have now found that probiotics in the intestine can also cause bacteria found there to function less effectively or even turn completely against their host.
A recent study by Washington University in St. Louis found that probiotics not only have a positive effect on our intestines. Probiotics can lead to health problems. The results of the study were published in the English-language journal "Cell Host and Microbe".
Microbes in the gut are important for health
Various studies have already shown how important the microbes in our gut are for our health and how they even affect our risk of cancer, depression and diabetes. Probiotics are said to restore intestinal balance, cure certain food allergies, or increase the effectiveness of antibiotics. In the worst case, the actually healthy bacteria can get out of control in the intestine and lead to an unpleasant feeling of fullness, forgetfulness and mental confusion.
Bacteria can change their mode of action
In the intestine there is a delicate balance between healthy and unhealthy bacteria. This complicated system can adapt to new conditions over time and bacteria can change their abilities and effects in the body. If living beings are used as medicines, it must be clear that they will adapt in the body. The researchers say there is no microbe that is immune to evolution. This is no reason not to develop probiotics-based therapies now, but it is important to do more research to better understand how and under what circumstances the bacteria in the body change, the authors add.
How was the experiment set up?
The current study looked at how a probiotic known as E. coli Nissle (EcN) adapts to the different conditions in the gut of mice. During the study, groups of mice with different types of gut microbiomes started eating different forms of food. After five weeks, the researchers examined the DNA of the probiotics in the intestine to see how it had changed under these different combinations. There were four groups with different types of gut microbiomes. One group had a normal gut microbiome with healthy bacteria. One group had a normal gut microbiome treated with antibiotics. The third group had no bacteria present in the gut and the last group had a limited diversity microbiome that mimicked an unhealthy gut. The animals received three different forms of nutrition. One group regularly ate mouse food in the form of a high-fiber diet that was designed to mimic the animals' natural diet. Another diet included pellets that were high in fat and sugar, low in fiber and reminiscent of a modern Western human diet. The last form of nutrition contained the pellets in the style of a western diet with fiber additives.
What effects have been observed?
At the end of the five weeks, the DNA of the microbes was analyzed. The team found that probiotics had adapted fairly well in animals with less healthy microbiomes and nutrition, while there was not much evolution in the healthy mice. In the case of diets with a high sugar content, the probiotics changed in order to be able to absorb more types of sugar. If the bacteria encountered antibiotics, they quickly developed resistance to them. Other bacteria even developed the ability to consume the intestinal mucosa and effectively turn against the host.
Results could improve future treatments
Evolution is a matter of course. The principles of evolution can be used to develop a better therapeutic that is carefully tailored to the individual. The team of researchers explains that understanding how gut probiotics develop can lead to more personalized treatments based on a person's microbiome, which can help treat a range of diseases. The researchers used the results to develop a potential probiotic treatment for a metabolic disorder called phenylketonuria. People with this disorder are unable to metabolize phenylalanine, which can cause brain damage at a high level. Genetically modified mice that were unable to process phenylalanine were added a gene that the bacteria could use to break down phenylalanine. In fact, the phenylalanine level was halved in a day in some mice. (as)