Encapsulated donor faeces for faecal microbiota transplantation: the Glyprotect protocol.

Background: Faecal microbiota transplantation (FMT) is a highly effective treatment for Clostridioides difficile infection. Its use is backed by solid evidence, but application methods differ. Encapsulated FMT is a non-invasive, patient-friendly and scalable application method that may be preferred over colonoscopy or nasoduodenal tube application.

Objectives: We describe a detailed protocol, the Glyprotect protocol, for producing glycerol-based capsules to increase FMT accessibility.

Design: Using iterative quality improvement methods, we developed and validated the Glyprotect protocol as a reproducible protocol for cryopreserving minimally processed donor faeces in a standard hospital laboratory setting.

Methods: We describe detailed standard operating procedures for producing glycerol-based capsules, including all necessary materials and troubleshooting guidelines. Capsule integrity was tested at various temperatures and pH levels. Flow cytometry was used to measure microbiota counts and dose accuracy.

Results: The Glyprotect protocol has been used for more than 2500 capsule-based FMT treatments and complies with European tissue and cell standards. The protocol is optimised to preserve microbes and minimise modulation of the donated microbiota by removing debris and water, which also reduces the number of capsules needed per FMT treatment. The intestinal microbiota is preserved in glycerol for cryoprotection and to prevent capsule leakage. Each capsule contains 650 µL microbe-glycerol mass, estimated to contain an average of 2.5 × 10⁸ non-specified bacteria.

Conclusion: The Glyprotect protocol enables hospitals and tissue establishments to set up capsule production in a standard laboratory, improving patients' access to FMT. The protocol facilitates the scalability of FMT services because capsule FMT is less time-consuming and less expensive than liquid-suspension FMT applied by colonoscopy or nasojejunal tube.

Trial registration: Not applicable.