# Fecal Microbiota Transplantation Donor Screening: Is Dientamoeba fragilis a Valid Criterion for Donor Exclusion? A Longitudinal Study of a Swiss Cohort

## TL;DR

This study investigates whether Dientamoeba fragilis in fecal microbiota transplant donors affects treatment outcomes for Clostridioides difficile infection.

## Contribution

The study provides longitudinal evidence on D. fragilis transmission and clinical impact through FMT in a Swiss cohort.

## Key findings

- D. fragilis was detected in 43% of FMTs from positive donors.
- Four recipients tested positive post-FMT from D. fragilis-positive donors.
- No significant differences in efficacy or adverse events were found between D. fragilis-positive and -negative FMTs.

## Abstract

Dientamoeba fragilis is a protozoan of the human digestive tract, yet its transmission and pathogenic role remain poorly understood. This study aimed to evaluate its impact on the efficacy and safety of fecal microbiota transplantation (FMT) in treating recurrent Clostridioides difficile infection (rCDI). This longitudinal cohort study analyzed stool samples from FMT donors and recipients pre-treatment and at 2 and 8 weeks post-FMT. All samples were retrospectively tested using real-time PCR. Shotgun metagenomics was also performed on selected donor–recipient pairs to explore transmission. CDI cure rates, gastrointestinal adverse events (AEs), and serious adverse events (SAEs) were assessed prospectively. A total of 53 FMT were analyzed (179 samples), with 23 (43%) derived from D. fragilis-positive donor stool (4 of 10 donors, 40%). Four of 52 recipients (18.2%), initially negative and who received treatment from positive donors, tested positive post-FMT. Shotgun metagenomics could not definitely confirm transmission due to the lack of a good reference genome. No significant differences in efficacy, AE, or SAE were observed between FMT from D. fragilis-positive versus -negative donors, even in immunocompromised patients. No SAEs were attributed to FMT. D. fragilis may be transmitted via FMT without evidence of short-term clinical impact. Consequently, RT-PCR detection should be interpreted cautiously in the context of donor exclusion decisions.