Dry alginate beads for fecal microbiota transplantation: From model strains to fecal samples

Clostridioides difficile infection (CDI) is a critical nosocomial infection with more than 124,000 cases per year in Europe and a mortality rate of 15-17 %. The standard of care (SoC) is antibiotic treatment. Unfortunately, the relapse rate is high (similar to 35 %) and SoC is significantly less effective against recurrent infection (rCDI). Fecal microbiota transplantation (FMT) is a recommended treatment against rCDI from the second recurrence episode and has an efficacy of 90 %. The formulation of diluted donor stool deserves innovation because its actual administration routes deserve optimization (naso-duodenal/jejunal tubes, colonoscopy, enema or several volu-minous oral capsules). Encapsulation of model bacteria strains in gel beads were first investigated. Then, the encapsulation method was applied to diluted stools. Robust spherical gel beads were obtained. The mean particle size was around 2 mm. A high loading of viable microorganisms was obtained for model strains and fecal samples. For plate-counting, values ranged from 10(15) to 10(17) CFU/g for single and mixed model strains, and 10(6) to 10(8) CFU/g for fecal samples. This corresponded to a viability of 30 % to 60 % as assessed by flow cytometry. This novel formulation is promising as the technology is applicable to both model strains and bacteria con-tained in the gut microbiota.

Automated summary

Clostridioides difficile infection (CDI) is a severe nosocomial infection with a high mortality rate. Although antibiotic treatment is the standard of care, the relapse rate is high and less effective against recurrent infection. Fecal microbiota transplantation (FMT) is a recommended treatment with a high efficacy. The formulation of diluted donor stool needs innovation, and the administration routes should be optimized.