What Is a Fecal Transplant? (Gross, Yes, But Also Life-Saving)

What is a fecal transplant and who would want one? It all boils down to your gut microbiota. Ask Science explains.

Sabrina Stierwalt, PhD
5-minute read
Episode #295

We have roughly the same amount of bacterial cells in our body as we do human cells, if not more. Our microbiome of bacteria, fungi, and viruses are populated by more than 10,000 different species that help protect us against infections and even assist in our reproductive health. The microscopic creatures living in our gut specifically help us digest food, aid our metabolism, and fight off gastrointestinal infections. In fact, our gut microbiome plays such an important role in our health that doctors are looking at ways to harness that power for fighting off infections.

Harnessing the power of the gut microbiome may sound pretty sophisticated, but what I’m really talking about here is poop. Specifically, poop transplants. How do poop transplants work and why would someone go in search of a poop donor in order to get a transplant?

What Is a Fecal Transplant?

A fecal (or stool or insert other of your favored words for poop here) transplant—also called a fecal microbiota transplantation (FMT for short) or, more generally, bacteriotherapy—is the transfer of stool from a person with a healthy gut microbiome to a sick person whose gut bacteria has somehow been disturbed from its natural order. The transfer is usually done directly to the colon or large intestine via a colonoscopy. Fecal transplants can also be done by a tube inserted into a patient’s stomach or sometimes by pill.

In standard medical practice, the majority of fecal transplants are used to treat an infection known as Clostridium Difficile (or C. diff). C. diff typically arises when a patient has taken a strong course of antibiotics that ends up killing too much of the desirable bacteria in the digestive tract. This can irritate the colon and cause painful, intense diarrhea that can even lead to death. One particularly horrific-sounding result of C. diff is known as toxic megacolon, where the colon becomes dangerously enlarged.

As many as half a million people in the United States suffer from C. diff annually and the infection results in as many as 15,000 deaths per year, usually among the elderly. C. diff infections and their associated treatments are also estimated to cost healthcare facilities in the United States $496 million and insurance companies over $547 million.

C. diff infections are most commonly treated with antibiotics but with limited success, particularly because antibiotics often caused the infection to begin with. Antibiotics disturb the healthy microorganisms, the very ones needed to fight off the C. diff, and the most common strains of C. diff are antibiotic-resistant.

Fecal transplants offer a potential simple, effective, and cheap alternative. By placing a healthy person’s stool, and the healthy microorganisms that come with it, into the sick patient’s colon, the balance of good versus bad bacteria can be re-established. The “good” bacteria competes with the C. diff and inhibits the invading infection’s growth.

Fecal transplants aren’t entirely new. There is some evidence that they were used in ancient Chinese medicine, offered in the form of yellow "soup," to treat food poisoning and severe diarrhea. Veterinarians also use a practice called transfaunation to transfer stomach microorganisms from a healthy animal to a sick one, like through cud from cows.

But how effective are fecal transplants? Broader studies still need to be done on larger groups of patients in order to definitively determine the effectiveness of sharing stool, but the initial results are promising. In a recent clinical trial, 20 patients with C. diff were given treatment: 9 had fecal transplants and 11 had a 10-day course of antibiotics. Five patients in each group were cured, as in they did not see a recurrence of the infection within 70 days. The four patients not cured by the transplants were then given antibiotics which cleared the infection for two of them.


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About the Author

Sabrina Stierwalt, PhD

Dr Sabrina Stierwalt earned a Ph.D. in Astronomy & Astrophysics from Cornell University and is now a Professor of Physics at Occidental College.