Recently, a growing number of studies have discovered diseases that are connected with changes in the gut’s microbiota.
Cancer, obesity, depression, and post-traumatic stress disorder are only some of the conditions that researchers have linked with an imbalance in the bacterial composition of our gut.
This imbalance bears the name “dysbiosis,” and observational studies have noted a link between microbial dysbiosis and allergies, irritable bowel syndrome, and cardiovascular disease.
More recently, Medical News Today reported on research that found connections between gut bacteria and age-related diseases, such as Alzheimer’s or age-induced paralysis.
Many of the studies that have illuminated these connections have been conducted in germ-free mice. In these tests, researchers replaced the rodents’ gut microbiotas with healthier bacteria by performing fecal transplants from a healthy donor.
Physicians use the same procedure of stool transplantation in human clinical trials. But new research suggests that some stools are better than others — that is, so-called super donors have certain bacteria in their guts that can help restore the microbial diversity that is lost in conditions like inflammatory bowel disease and diabetes.
If researchers gain a better understanding of the mechanisms through which these super donor stool samples help cure chronic disease, fecal transplantation could be a safe and effective therapy for a wide range of illnesses.
With this rationale in mind, Justin O’Sullivan, Ph.D., of the University of Auckland in New Zealand, and colleagues set out to review existing clinical trials of fecal transplantation.
The team published its findings in the journal Frontiers in Cellular and Infection Microbiology.
Studying the effects of fecal transplants
The researchers examined existing trials of fecal transplantation for chronic diseases associated with dysbiosis, such as inflammatory bowel disease, allergic colitis, and constipation, as well as some liver, metabolic, and even neurological conditions.
“The pattern of success in these trials demonstrates the existence of ‘super donors,’ whose stool is particularly likely to influence the host gut and to lead to clinical improvement,” O’Sullivan reports.
The average cure rate when using fecal transplantation for diarrheal infection is over 90 percent, the researchers note, but for other conditions, such as IBD or type 2 diabetes, the average rate is around 20 percent.
But some transplants lead to outstanding results, O’Sullivan explains, continuing, “We see transplants from super donors achieve clinical remission rates of perhaps double the remaining average.”
“Our hope is that if we can discover how this happens, then we can improve the success of fecal transplantation and even trial it for new microbiome-associated conditions, like Alzheimer’s, multiple sclerosis, and asthma.”
Justin O’Sullivan, Ph.D.
Key features of super donor fecal samples
The researchers also describe some characteristics of these fecal samples from super donors.
Microbial diversity and high concentrations of “keystone species” of bacteria are among these characteristics. Keystone species are bacteria that trigger the production of chemicals — such as butyrate — without which the body is more vulnerable to disease.
“In inflammatory bowel disease and diabetes, for example,” explains O’Sullivan, “keystone species that are associated with prolonged clinical remission produce butyrate — a chemical with specialized functions in regulating the immune system and energy metabolism.”
The researchers’ analysis also reveals that the interplay between viruses, the diet, and the immune system all influence the existence and development of beneficial bacteria.
“For example, the success of fecal transplants has been associated in some studies with the transfer of viruses [that] infect other gut microbes,” says O’Sullivan.
“Some cases of recurrent diarrheal infection have even been cured with transplants of filtered stool that has had all the live bacteria filtered out but still contains DNA, viruses, and other debris.
“Supporting the transplanted microbiome through diet could also improve success,” adds the researcher.
“It has been shown that a rapid change in diet, such as a switch from an animal-based to an exclusively plant-based diet, can alter the composition of the gut microbiota within 24 hours.”
Justin O’Sullivan, Ph.D.
Finally, in light of the above, the researchers advise that human fecal transplant trials should take into account the donors’ genetic backgrounds and diets, in order to better predict the clinical outcomes of the intervention.
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