Novel alginate formulation for fecal microbiota transplantation: comparative and long-term stability evaluation

Fecal microbiota transplantation (FMT) is the reference treatment against recurrent Clostridioides difficile (rCDI) infection with an efficacy of 80-90 %. The current standard-of-care FMT formulation, frozen oral capsules, suffers from several drawbacks complicating treatment storage and administration. This observational study aimed to bridge current gaps in FMT treatment by proposing a novel formulation produced with alginate and evaluating the bacterial load, viability, and composition of the microbiota over a 24-month period. Twelve stool samples obtained from four different healthy donors were collected to produce two formulations each: frozen oral capsules and lyophilized alginate beads. The formulations' composition and viability were compared using plate-counting, flow cytometry, and metagenomic 16S amplicon sequencing. Additionally, the stability of the novel formulation was evaluated in a longitudinal study. Batches of particles contained up to 109 and 1014 viable bacteria, as assessed by plate-counting and flow cytometry, respectively. The novel alginate formulation was comparable to the oral capsules in terms of microbiota diversity measured by the metrics Chao1, Pielou, Shannon, Jaccard, and Bray-Curtis. Furthermore, the composition and viability of the alginate particles remained stable over time. A novel FMT formulation successfully encapsulated live bacteria in alginate, effectively preserving both the viability and stability of the bacterial composition over time.