Stool transplants: A way to bring gut bacteria back to health | Science| In-depth reporting on science and technology | DW | 16.09.2020
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Stool transplants: A way to bring gut bacteria back to health

We often don't like talking about our bowels, but they are of great importance for our overall health. And if they don't work properly, serious problems can occur. Sometimes stool transplants can help.

What is the correct medical language when talking about human solid body waste? S…? Excrement? Or feces?

The common name among doctors is stool, says Maria Vehreschild,  the head of Infectiology at the University Hospital in Frankfurt,  Germany.

She knows that hardly anyone likes to talk about stool in general and their own in particular. And to even imagine what it would be like to have someone else's stool transplanted into one's own body is probably a rather repulsive idea for most people.

But patients who are about to undergo a stool transplant  are hardly bothered by this, says Vehreschild. After all, it could mean an improvement in their state of health. "The psychological problems of the recipients are mainly caused by the fact that intestinal diseases are usually recurrent. In other words, they come back again and again. This troubles the patients more than anything else," says Vehreschild.

In addition to her work at the University of Frankfurt, Vehreschild also heads the Medical Microbiome Research working group at the University Hospital of Cologne.  She is considered an expert in the field of stool transplantation, also known as fecal microbiota transplantation (FMT).

FMT is known to help people with certain bowel conditions, as fecal bacteria from a healthy donor introduced into another person's gut can restore the balance of bacteria there, creating a better microbiome.

Bacteria of the human microbiome

There are trillions of bacteria living in our intestines

Influential microorganisms

Our microbiome is a kind of fingerprint, because it is unique to each person. Billions of bacteria and other microorganisms live in our intestines.

"The microbiome describes the genes of all microorganisms that colonize us," says Vehreschild. "The organisms themselves would be described as microbiota. They play a very important role in the regulation of our body functions. There is hardly an organ that is not influenced in its functions by the composition of the microbiome."

That is why, she says, science has in recent years come up with the idea that so-called microbiome-organ axes exist. Vehreschild gives as examples the intestine-brain axis, the intestine-liver axis and the intestine-kidney axis.

"They indicate that there are interactions between the microbiota and different organs," Vehreschild says.

Stringent tests

Before the donor's stool is transferred to the recipient, both have to undergo several tests and interviews. "These are even more detailed than for a blood donation. After all, we have to look for indications of possible infections in the blood and also in the stool," says Vehreschild.

There are different methods for subsequently transferring the stool and thus the bacteria it contains.

First of all, the stool donation must be prepared. "The donor comes to us in the laboratory and donates his or her stool. The donation is filtered and centrifuged to extract the bacteria it contains. We then pipette these bacteria into capsules that the patient swallows," says Vehreschild.

Bacteria of the human microbiome

About 50% of the human feces consists of bacteria

But capsules are not the only option. A transfer can also be performed during a colonoscopy.  And the helpful bacteria can also be introduced directly into the large intestine by means of an enema. They must then establish themselves there to help the intestine regenerate and fulfill its functions.

Important requirements

In Germany, not everyone who has problems with stomach and intestines  can receive a stool transplant. So far, only people with a so-called Clostridium difficile infection  are eligible as recipients.

This bacterium can cause severe intestinal inflammation with bloody diarrhea. The infection is often triggered by the repeated use of antibiotics, because such therapies always carry the risk of damaging the intestinal flora  and allowing disease-causing germs such as Clostridium difficile to spread.

A woman sitting on the toilet.

For some humans, going to the toilet becomes an ordeal

If none of the usual therapies has worked, doctors can try to help the sufferer with a stool transplant. In her experience, Vehreschild says, there is an average success rate of 75% after a single therapy. However, this method is still in its infancy, and little is known about the risks.

Vehreschild's team is currently concentrating on technically optimizing the microbiota transfer and preparing the donor's stool for transplantation in the best way possible.

Stool transplantation under research

Whether the method can also be applied to other intestinal diseases has not yet been sufficiently researched.

For example, physicians have already successfully performed stool transplantation on people with ulcerative colitis,  but only in a very small number of cases. This also applies to irritable bowel syndrome. 

In all these diseases, there is an imbalance in the intestinal flora. If scientists could treat such cases in the future with a stool transplant, this would be a blessing for many people, including those suffering from Crohn's disease.

The gastric wall

Our digestive system is a miracle

Not yet approved

Even though FMT seems to be quite successful, the method is still not an approved procedure in Germany, and its application is subject to strict conditions. One of the most important of these is that a physician must have performed all other possible therapies on the patient.  A stool transplant can be performed only if none of these has been successful and the indication Clostridium difficile is given.

But despite all the strict regulations, there are still risks, Vehreschild says. And, she says, these often worry potential recipients.

"On the one hand, the patients naturally want to know, and rightly so, what we are testing the donor for and whether we are certain that nothing dangerous can be transmitted," she says. "But there is, of course, a certain amount of uncertainty remaining. Take cancer, for example — is there perhaps a microbiome configuration that promotes the development of cancer? If we don't know anything on this score yet, then, of course, I can't point it out to the recipient."

A man drinking Belgian beer.

With the self-brewer syndrome, the body develops alcohol on its own

The auto-brewery syndrome

The story of a 47-year-old Belgian man shows what our gut microbiome is capable of.

This man didn't drink a sip of alcohol and yet he was continually drunk. The whole problem lasted about two months.

Doctors at the University Hospital of Ghent finally found the solution: The man was suffering from the so-called auto-brewery syndrome.  In this rare disease, the body produces too much ethanol, i.e. alcohol, after a meal with carbohydrates because of a particular yeast fungus. This meant that the man was constantly above the alcohol limit.

The doctors were able to help him with a stool transplant. So now he no longer has to see everything double.