Fecal microbiota transplantation (FMT) is used to prevent Clostridioides difficile infection and for the treatment of infections that are not responsive to standard therapies. However, prospective data on outcomes and safety are limited. An ongoing national registry study was designed to provide a real-world view of clinical practice, patient outcomes, safety, and the comparative effectiveness of FMT.

In the first two years of the study, 259 participants with post-FMT follow-up were enrolled at 20 sites. All patients who were diagnosed with C. difficile infection, which was moderate or mild in most cases, had undergone FMT.

Of the 222 patients for whom one-month follow-up data were available, 200 were cured of C. difficile infection, with 197 of these patients requiring only one transplant to achieve this. Of the 112 patients who were cured at one month and had a six-month follow-up, four had a recurrence of C. difficile infection post-FMT. Of the 11 patients in whom FMT failed initially and who were followed for six months, seven were cured of C. difficile infection at six months.

Three procedure-related complications were reported at one month. A total of 106 patients reported one or more post-FMT symptoms; 13 of the 212 symptoms reported were severe. Eleven patients had infections, two of which were thought to be related to the procedure. Twenty-seven patients were hospitalized within one month of FMT, most often for C. difficile infection recurrence. Six of 156 patients whose data was collected at six-month follow-up had one or more new infections, and 30 were hospitalized, most for an infection other than C. difficile.

Limitations of the study were missing or incomplete data, patients lost to follow-up, and the potential for recall bias when patients were queried at follow-up. Also, donor screening protocols varied at participating sites, and FMT and post-FMT practice was at the providers' discretion.