of these bacteria or imbalances in the growth of various bacteria may lead to
recurrent gastrointestinal issues and fecal bacteriotherapy would be required
to treat the condition.
have become a
routine treatment for multiple intestinal disorders including
recurrent diarrheal infections.
However, using fecal
transplants to treat other conditions has remained only in the experimental
Fecal Transplants and
team that believes in the potential of fecal transplants has attempted to
re-examine the evidence. On many occasions, they have spotted a single donor
whose stool was considerably more likely to lead to clinical improvement than
others in the same trial. Referred to as 'super-donors,' they will be able to
provide bacteria to restore the gut chemicals that would have become
nonexistent owing to illnesses like inflammatory bowel disease
Alzheimer's, multiple sclerosis, cancers,
asthma, allergies and heart disease are all related to changes in the gut
delving into what makes a fecal super donor would potentially help in finding
the solution to all these diseases.
O'Sullivan of the University of Auckland, who is also the senior author of the
research has said:
"The last two decades
have seen a growing list of medical conditions associated with changes in the
microbiome -- bacteria, viruses and fungi, especially in the gut."
He added, "In fact, we know
already that changes to the gut microbiome can contribute to disease, based on
studies in germ-free mice as well as clinical improvement in human patients
following restoration of the gut microbiome by transplanting stool from a
cure rate for recurrent diarrheal infection using fecal transplant exceeds 90
percent. Whereas, in the trials for others illnesses like inflammatory bowel
disease exacerbations and type-2 diabetes, it has been mixed, averaging a cure
rate of 20 percent.
"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
On why it is important to understand
super-donors, he mentioned: "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
What Makes 'Super-Donors'
O'Sullivan and his colleagues have reviewed many fecal transplantation trials
to find evidence that will help understand the origin of super-donor
phenomenon. He explains:
"It is well-known that
responders typically exhibit a higher microbial diversity than non-responders.
In line with these observations, a larger number of species in the donor stool
has been shown to be one of the most significant factors influencing fecal
High levels of specific 'keystone species' are
commonly found in super-donor stools.
These are the species
of bacteria that produce chemicals whose absence may contribute to diseases in
the host gut. Dr. O'Sullivan illustrates this point with the following example,
"In inflammatory bowel disease and diabetes, for example,
keystone species that are associated with prolonged clinical remission produce
butyrate - a chemical with specialized functions in regulating the immune
system and energy metabolism."
There is a
possibility of testing the keystone species theory - donor stool rich in
particular strains could be selected or 'precision' transplants with a defined
mixture of beneficial bacteria, like a probiotic
could be designed.
"This approach has been applied successfully to
prevent complications in a small sample of patients with liver disease.
However, this study showed that microbial enrichment in the donor does not
completely guarantee enrichment in the recipient,"
What makes a Fecal Transplant Successful?
of the keystone species alone does not render a super donor. There are many
other influencing factors like the balance
of other bacteria present and the interactions between them which determine the
retention of the keystone species.
research has also revealed that is not only the bacteria type that matters but
also what's present in and around the bacteria. The following statement
explains this point - "For example, the
success of fecal transplants has been associated in some studies with the
transfer of viruses which infect other gut microbes. 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. These viruses could affect the survival and metabolic
function of transplanted bacteria and other microbes."
The Way Forward
O'Sullivan and team recognize that super-donors
may not solely account for success in fecal transplantation.
They have been
quoted saying that, "Some fecal
transplant failures may be attributable to the gut's immune response to
transplanted microbes, possibly stemming from an underlying genetic difference
between the donor and the recipient."
that "Supporting the transplanted
microbiome through diet could also improve success. 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
conclusion, the team recommends that the genetic background and dietary intake
of recipients should be recorded in all future fecal transplant trials. This
would immensely help in understanding better, their impact on transplant
engraftment and clinical remission.
- The Super-Donor Phenomenon in Fecal Microbiota Transplantation - (https://www.frontiersin.org/articles/10.3389/fcimb.2019.00002/full)