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Fecal grafts have become routine treatment for recurrent and unpleasant diarrheal infections, but trials for other conditions have not yet been completed. Now scientists have re-examined the evidence.
Time and again, they found a donor whose stool was significantly more likely to lead to clinical improvement than others in the same trial. These "super donors" can provide the bacteria needed to restore intestinal chemicals that are lacking in diseases such as IBD and diabetes, according to a new journal published in The boundaries of cellular and infectious microbiology. With Alzheimer's disease, multiple sclerosis, cancer, asthma, allergy and heart disease, all badociated with changes in gut bacteria, understanding what makes a super stool donor could make crap the new panacea.
Fecal grafts of super donors have high success rates
"The last two decades have seen a growing list of medical conditions badociated with changes in the microbiome – bacteria, viruses, and fungi, particularly in the intestine," said Dr. Justin O. Sullivan, lead author of the University of Auckland.
"In fact, we already know that changes in the intestinal microbiome may contribute to the disease, based on studies conducted on germ-free mice and clinical improvement in human patients after the restoration of the Intestinal microbiome by stool transplantation from a healthy donor. "
Although the overall cure rate for recurrent diarrheal infections exceeds 90%, fecal transplantation tests for other conditions such as exacerbations of inflammatory bowel disease and type 2 diabetes have had much more mixed results, the average 20%.
"The successful model of these trials demonstrates the existence of" super-donors "whose stool is particularly likely to influence the host's bowel and lead to clinical improvement ", explains O & # 39; Sullivan.
"We are seeing super-donor grafts reaching clinical remission rates as high as double the average remaining, and we hope that if we can find out how this happens, then we can improve the success of fecal transplantation and even to test for new conditions badociated with the microbiome such as Alzheimer's disease, multiple sclerosis and asthma ".
Super stool is rich in bacteria that improve our metabolism
O & # 39; Sullivan and colleagues examined faecal transplant tests to find clues about the origin of the super-donor phenomenon.
"It is well known that responders generally have higher microbial diversity than non-responders, and in accordance with these observations, more of the species found in the donor's stool have been found to be present. 39, one of the most important factors affecting the outcome of fecal transplantation, "explains O. Sullivan.
In particular, the stool of super-donors tends to contain a high number of key species. These are bacteria that produce chemicals whose absence in the intestines of the host contributes to diseases.
"In inflammatory bowel disease and diabetes, for example, key species that are badociated with prolonged clinical remission produce butyrate – a chemical with specialized functions in the regulation of the immune system and energy metabolism." . "
Of course, key species theory can be tested by selecting donor stools rich in particular strains – or by designing "precision" grafts with a definite mix of beneficial bacteria, such as a probiotic.
"This approach has been successfully applied to prevent complications in a small sample of patients with liver disease.However, this study has shown that microbial enrichment in the donor does not completely guarantee the patient." 39, enrichment in the recipient. "
Viruses, immunity and diet also affect the success of fecal transplantation
It is clear that super-donors are not limited to key species.
The balance of other bacteria present and the interactions between them seem to affect the retention of key species.
But by digging deeper into the stool samples, the researchers found that it was important not only to know which bacteria were present, but also the presence in and around the bacteria.
"For example, the success of fecal transplants has been badociated in some studies with the transfer of viruses that infect other intestinal microbes.Some cases of recurrent diarrheal infection have even been cured with filtered stool transplants, all live bacteria that have been filtered still contain DNA, viruses and other debris.
"These viruses could affect the survival and metabolic function of bacteria and other transplanted microbes."
Abandonment of the approach "a stool suitable for all"
In the end, O & # 39; s Sullivan and colleagues recognize that super-donors may not be at the origin of a successful fecal transplant.
"Some failures of fecal transplantation may be attributable to the immune response of the gut to transplanted microbes, which may result from an underlying genetic difference between the donor and the recipient."
"Supporting the microbiome-grafted diet could also improve success.It has been shown that a rapid change in diet, such as switching from an animal-based diet to an exclusively plant-based diet, can change the composition of the microbiota hours. "
They recommend that future fecal transplant tests routinely record information on the recipients' genetic history and food intake, so that we can better understand their impact on engraftment and clinical remission.
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