It isn’t very often that a medical procedure inspires a patient-advocacy movement, let alone an Internet fan club. Especially not a procedure that is, well, icky. But that’s undeniably what has happened with fecal transplants, a low-tech practice from back in medical history that has worked its way from outlaw home procedure to papers in major medical journals and a Food and Drug Administration clinical trial.

In case you’ve missed all of this: Fecal transplants are just what they sound like. They involve taking one person’s feces and putting them inside the colon of someone else. The reason, usually, is because the assortment of bacteria that live in the recipient’s guts have gotten gravely out of balance, and the bacteria that make up most of the donor’s feces (and yours and mine) rebalance things back where they ought to be.

The cause of the imbalance, usually, is a serious illness caused by a bacterium called Clostridium difficile, or C. diff for short. And that’s where the short film above, being released first here, comes in.

C. diff illness occurs when gut bacteria are destroyed by taking antibiotics. The various communities of bacteria, also known as the gut microbiome, usually keep each other in check, but when that ecosystem becomes disordered, C. diff seizes the spare living space to reproduce. The bacteria produce toxins that harm cells in the intestines, causing diarrhea that resists treatment, recurs frequently, and can be deadly. More than 250,000 people get C. diff infection each year, and 14,000 die. (Here’s the CDC’s best information on C. diff infection, a story I wrote for WIRED about it, and one from National Geographic.)

C. diff infection not only is caused by antibiotic use; it is also treated with antibiotics. That pushes patients into a downward spiral in which the microbiome slides further out of balance, C. diff bacteria proliferate, more antibiotics are given, and so on all the way down. Fecal transplants stop that spiral cold. After one treatment, they cure C. diff infection 94 percent of the time, compared t0 31 percent for antibiotics.

But, legally, fecal transplants (sometimes known as FMT, for “fecal microbiota transplantation”) are problematic: Are they a drug? Or a donated tissue, like a cornea? Should the Food and Drug Administration regulate them? Does it even know how?

Director Michael Graziano knew none of this when he began researching his 2014 film Resistance, which examines what happens when antibiotics no longer work, through patients’ heartbreaking stories and lost archival footage. (Disclosure: I am in it.) One of the families he encountered was the Guintinis of Tennessee, whose 15-year-old daughter developed C. diff after she received powerful antibiotics for a MRSA infection. After two years of doctors’ trying to cure it, and Lauren getting worse and worse instead, the family learned about FMT. The film shows what happened next.

I asked Graziano a few questions about why he decided to spend months of his life making art about someone else’s poop.

Maryn McKenna: What made you decide to tell the story of FMT?
Michael Graziano: While making Resistance I developed a strong interest in the human microbiome, and the way our burgeoning understanding of the ecology of microbes that lives in and on us is shaping the frontier of human health. I’d never heard of C. diff and FMT, and once I learned about them I discovered hardly anyone I spoke with knew about them either. This made me think I should try to help fill that knowledge gap.

A fecal transplant is a pretty intimate thing. How did you convince this family to participate?
I’ve been fortunate to work with some candid, open and honest physicians, researchers and patients, including at Vanderbilt University Medical Center. One introduced me to Dr. Maribeth Nicholson, a gastroenterologist at Vanderbilt who appears in this film and frequently performs FMTs. Lauren was her patient, and Dr. Nicholson told her and her family about my project. They told me they wished they’d had more information when they first learned Lauren had the infection. They agreed with helping other families going through the same ordeal.

FMT is still considered a bit outlaw by parts of the medical establishment. Did it feel that way to you?
There are aesthetic reasons for the slow uptake: the “yuck factor.” There are also some concerns about long-term implications of the procedure, because it is not 100 percent understood. But, once I looked at the number of peer-reviewed journal articles that demonstrate the outstanding efficacy of FMT, and talked with physicians who perform them, the value became crystal clear.  The data suggest an incredibly high safety profile—zero adverse events!—compared to the very real and alarming concerns associated with antibiotics.

Can you see this becoming more widespread?
I can, as more people and physicians learn about it. But there are challenges. The medical system understands antibiotics; there are clear business and regulatory structures in place. This structural comfort doesn’t exist with FMT. Despite the fact that FMT can obviate the need for antibiotics, its clear effectiveness, and the crisis of resistant infections we’ve created by overusing antibiotics, there’s no clear business model for FMT, and the regulatory guidelines are still not 100 percent clear.