A new study from Washington University School of medicine in St Louis says that probiotics are living bacteria. They are taken to improve digestive health. They are able to evolve when inside a body and can become less effective or harmful.
On March 26th, findings suggesting that probiotics are not a one-size-fits-all therapy were published. A probiotic can be effective on one person and harmful or ineffective on another person. Serious infections have been linked with probiotics.
Gautam Dantas, Ph.D., a senior author said if we are to use living things like medicine, we should realize they will adapt. No microbe is immune to evolution. We should understand the conditions under which probiotic-based therapies change.
Everybody’s digestive tracts host a lot of viruses, fungi and bacteria called the gut microbiome. It serves the purpose of supplying us with vitamins, digesting food, regulating inflammation and monitoring disease-causing microbes. The marketing of dietary supplements and probiotics in foods is to keep digestion running smoothly and healthy bacteria plentiful.
They are also developed for the treatment of serious medical conditions like inflammatory bowel disease. For it to be used on people, the probiotic-based treatment should be proven effective and safe. This will be a problem considering the therapy can change once administered since it is a living thing.
The major step to creating safe and effective probiotic therapeutics is understanding the principles governing evolution in the digestive tract. The researchers turned to a probiotic called E. coli Nissle 1917 isolated from a World War I soldier. He came out unaffected by an epidemic of severe diarrheal disease that made his comrades sick.
The mice study
The researchers studied the way the probiotic responded to different microbial communities using mice. The mice harbored four kinds of gut microbiomes. They gave mice the probiotic and then fed them with different types of food. Five weeks later, the bacteria were obtained from the mice’s guts and the DNA of the microbes analyzed.
Ferreiro said that they did not capture a lot of adaptation in a healthy, high-diversity background. This could have been because that was the background that Nissle was used to.
These findings were applied by Dantas and his colleagues to design a probiotic therapy for PKU. It is not possible for people with PKU to breakdown phenylalanine. A high level of it causes brain damage.
A gene was inserted into Nissle which enabled it to degrade phenylalanine and the bio-engineered bacteria were given to mice that were not able to metabolize phenylalanine. By the next day, its levels had reduced by half in some mice.
After a week of treatment, researchers never found major changes to the engineered strain’s DNA. This suggests that over short time scales, the use of Nissle for probiotic therapies could be safe.
Dantas said that evolution was given and we should embrace it so as to design a better therapeutic.
- Medicine, W. U. (2019). medicine.wustl.edu. Retrieved 04 17, 2019, from Medicine: https://medicine.wustl.edu/news/probiotic-bacteria-evolve-inside-mices-gi-tracts/