How did a stool transplant go from last resort to tested medicine?

A stool transplant, formally a fecal microbiota transplant, moves gut microbes from a healthy person into someone whose gut community has been wrecked. It is the process of transferring fecal bacteria and other microbes from a healthy individual into an unhealthy individual, and for one illness it has turned from oddity to tested medicine. The illness is recurrent C. difficile infection, where FMT is more effective than the antibiotic vancomycin alone. It is approximately 85 to 90 percent effective in people for whom antibiotics have not worked or in whom the disease keeps coming back, and most patients recover with a single treatment.

The idea has a long and strange history. In the Ming dynasty, the physician Li Shizhen used a "yellow soup" containing fresh, dry or fermented stool to treat abdominal diseases. In western medicine the first published use came in 1958, when a team of Colorado surgeons led by Ben Eiseman used fecal enemas on four critically ill people with severe colitis, in a time before C. difficile was known as the cause. They returned to health rapidly.

The proof came much later. The first randomised controlled trial in C. difficile infection was published in January 2013 and was stopped early because FMT worked so well: 81 percent of patients were cured after a single infusion and over 90 percent after a second.

It is still not a casual treatment. Side effects include a risk of infections, so donors must be screened for pathogens. In 2019 a person in the United States died after receiving an FMT that contained drug-resistant bacteria, and another recipient of the same transplant was also infected.

Approved products have followed: in 2022 in Australia and the United States, and in 2023 the first fecal microbiota product taken by mouth.