II. 6 Donor screening and the safety of the product

It is reassuring to know what stands behind your capsule: strict donor screening to international standards, blood testing done twice, an extensive pathogen panel and controlled manufacturing. Here you will get to know the full chain of safety.

The donor's journey – the strict screening

The contents of a DiffBiome capsule come from a healthy human donor^[G] – but for someone to become a donor, they must pass through a great many filters. The aim is twofold: on the one hand to ensure that the donor's flora is healthy, diverse and valuable, and on the other to exclude any risk that could deliver infections or other pathogens to the recipient^[G].

Donor screening^[G] is not a one-off test but a carefully constructed process that follows international professional standards. It begins with a detailed health and lifestyle questionnaire, which excludes a great deal: if someone has inflammatory bowel disease, for example, that is an outright exclusion criterion. We also pay attention to the donor's diet: the animal protein they eat must be free of antibiotics and anthelmintics, because these substances would reach the donor's gut flora through the meat and could degrade the quality of the graft. That is why we do not leave it to commercial supply: the MicroBiome Bank runs its own farm under the name Cservölgy Major, keeping goats, sheep and cattle – so this part of the donors' diet stays under our control throughout.

One cornerstone of the screening is that we carry out the blood test not once but twice, eight weeks apart. This matters because some infections have a "window period" during which they cannot yet be detected – the twofold, time-separated testing closes this gap. Only a donor who passes both rounds can proceed.

The safety of the product – from manufacturing to the capsule

From here, the screened donor's flora enters a controlled manufacturing process. We clear the raw material of pathogens, convert it into a living bacterial suspension, then dry it gently and fill it into capsules. The process is not industrial mass production but proceeds according to strict quality standards – so-called GMP, good manufacturing practice: we check every batch, among other things to ensure that it contains enough viable bacteria and nothing that it should not.

Every dose receives a traceable identifier, a so-called LOT number. This is like a birth certificate: it tells exactly which donor, when and from which batch your capsule was made. This is why it is important always to write the LOT number in your diary – if any question should arise, any dose can be traced this way. The LOT system also makes it possible to switch to another batch if needed.

The capsule contains not only living bacteria but also a few excipients that feed and stabilise the flora. These are all known, safe substances. The unopened bottle is best kept in a dark, cool place, standing upright – storage too has its own rules, so that the bacteria stay viable. This whole chain – from screening through manufacturing to storage – together provides the safety on which your course is built.

🍽️ Eating during these days

In these three days you come to know the product's chain of safety – donor screening, manufacturing and storage – while your diet continues to follow the gentle, firming line. Your tasks: take the daily dose according to the usual routine, drink an extra glass of water after every looser stool, and do not forget to write the LOT number in your diary, and to store the unopened bottle in a cool, dark place, standing upright.

For these days, the Plant Calendar recommends sources providing gentle, soluble fibre and resistant starch: on day 19 oats (the beta-glucan in them is a soluble fibre, gentle on the gut), on day 20 cooked carrot (soluble fibre, soothing in effect), and on day 21 cooked, cooled potato, in which resistant starch forms during the cooling. These fibres feed the good bacteria in the colon and support a firmer stool while your symptoms settle. Build the plant of the day into at least one meal, cooked or steamed; if you do not tolerate one of them well, leave it out and return to it later.

Why does this matter?

If you know what strict screening and controlled manufacturing your capsule goes through, it is easier to continue the course with trust and calm. Logging the LOT number is your part in this chain of safety: with it, every dose stays traceable – which serves your safety.

References

[015] Marcella C, Cui B, Kelly CR, Ianiro G, Cammarota G, Zhang F. Systematic review: the global incidence of faecal microbiota transplantation-related adverse events from 2000 to 2020. Aliment Pharmacol Ther. 2021. Link

Systematic review of FMT safety summarizing adverse events (AEs) over 20 years from 129 studies including 4,241 patients and 5,688 FMT courses (search of EMBASE, MEDLINE, Cochrane, CNKI, Wanfang from 2000 to 2020). AEs were classified as delivery-related or microbiota-related. The review provides the largest aggregate FMT safety dataset to date and supports the overall favourable safety profile of FMT for recurrent CDI, while flagging that complications may be under-reported in the literature.

[016] Cammarota G, Ianiro G, Tilg H et al. European consensus conference on faecal microbiota transplantation in clinical practice. Gut. 2017. Link

European consensus conference developing evidence-based recommendations on FMT for clinical practice, with 28 experts from 10 countries collaborating in working groups. Statements were generated through evidence-based review, evaluated electronically via a Delphi process, and finalized in a plenary consensus session. Recommendations cover FMT indications, donor selection, faecal material preparation, clinical management, faecal delivery, and minimum requirements for establishing an FMT centre. Provides the European standardization framework for safe and governed FMT delivery.

[033] Dethlefsen L, Relman DA. Incomplete recovery and individualized responses of the human distal gut microbiota to repeated antibiotic perturbation. Proceedings of the National Academy of Sciences of the United States of America. 2011. Link

Stanford-based longitudinal study tracking the gut microbiota of three individuals over 10 months across two consecutive courses of ciprofloxacin, with deep 16S rRNA sequencing. Loss of bacterial diversity was profound and rapid, occurring within 3-4 days of antibiotic initiation, and recovery toward the pre-treatment state was often incomplete months after cessation. Repeated antibiotic exposure produced incremental, non-recoverable shifts in community composition. With over 2,000 citations, this paper is the canonical reference establishing that antibiotic-induced dysbiosis is not a self-correcting disturbance but can leave a lasting ecological imprint – central to the case for MTT in patients with cumulative antibiotic exposure history.

[046] Chen RA, Wu WK, Panyod S, Liu PY, Chuang HL, Chen YH, Lyu Q, Hsu HC, Lin TL, Shen TD, Yang YT, Zou HB, Huang HS, Lin YE, Chen CC, Ho CT, Lai HC, Wu MS, Hsu CC, Sheen LY. Dietary Exposure to Antibiotic Residues Facilitates Metabolic Disorder by Altering the Gut Microbiota and Bile Acid Composition. mSystems. 2022. Link

Empirical study quantifying how chronic dietary exposure to subtherapeutic antibiotic residues (specifically tylosin at theoretical maximum daily intake, or TMDI, doses) alters gut microbiota composition and bile acid metabolism, producing measurable metabolic dysfunction in animal models. The obesity-related phenotype was transferable to germ-free recipient mice, indicating the effect is mediated by the altered microbiota itself. Early-life exposure produced lasting metabolic consequences via FGF15 signalling. Provides the most current empirical evidence cited in Section 8.2 supporting the categorical exclusion of conventional antibiotic-treated animal protein from donor and post-MTT recipient diets.

[097] Palleja A, Mikkelsen KH, Forslund SK et al. Recovery of gut microbiota of healthy adults following antibiotic exposure. Nature Microbiology. 2018. Link

Shotgun-metagenomic study of 12 healthy men: after a 4-day course of three last-resort antibiotics (meropenem, gentamicin, vancomycin) the gut microbiota largely but incompletely recovered over six months — several common species stayed missing and resistance genes were transiently enriched.

[098] Karmisholt Grosen A et al. Effects of clinical donor characteristics on the success of faecal microbiota transplantation for patients in Denmark with Clostridioides difficile infection: a single-centre, prospective cohort study. The Lancet Microbe. 2025. Link

Single-centre, prospective Danish cohort: clinical donor characteristics — including antibiotic exposure in the 12 months before donation and donation stool consistency — affect FMT success in recurrent C. difficile infection; donor antibiotic use worsens outcomes, supporting strict donor screening.

[100] Kelly CR, Ihunnah C, Fischer M, Khoruts A, Surawicz C, Afzali A, Aroniadis O, Barto A, Borody T, Giovanelli A, Gordon S, Gluck M, Hohmann EL, Kao D, Kao JY, McQuillen DP, Mellow M, Rank KM, Rao K, Ray A, Schwartz MA, Singh N, Stollman N, Suskind DL, Vindigni SM, Youngster I, Brandt L. **. American Journal of Gastroenterology. 2014. Link

Clostridium difficile infection (CDI) is especially dangerous in immunocompromised patients, yet the safety of fecal microbiota transplantation (FMT) in this group had been uncertain. This 16-centre retrospective series studied 80 immunocompromised patients (75 adults, 5 children) whose CDI was recurrent (55%), refractory (11%) or severe/overlapping (34%); causes of immunocompromise included HIV/AIDS, solid-organ transplant, oncologic disease, inflammatory bowel disease immunosuppression and other conditions. The CDI cure rate after a single FMT was 78%, and the procedure was generally safe: serious adverse events within 12 weeks were uncommon and did not indicate FMT-transmitted infection. The authors conclude that FMT is an effective and safe option for CDI even in immunocompromised patients.

[735] Cammarota G, Ianiro G, Kelly CR et al. International consensus conference on stool banking for faecal microbiota transplantation in clinical practice. Gut. 2019. Link

This international consensus from FMT experts in Europe, North America and Australia provides statements on stool banking for FMT, covering general principles, organization, donor selection and screening, stool collection/preparation/storage, services and clients, registries, outcome monitoring, ethics and FMT's evolving clinical role. Consensus was achieved through Delphi rounds plus plenary discussion, with statements supported by best available evidence. The document guides global stool-bank development to promote safe, equitable FMT access for recurrent C. difficile infection.