SwissGut - The Healthy Swiss Microbiome

Objective:

This study is designed to address the complex interplay between the gut microbiome, environmental factors, and inflammatory diseases, with a specific emphasis on serving as a healthy cohort for several related projects.

Primary hypotheses:

Since data from this study will be used as control data for four studies, four primary hypothesis will be defined.

Hypothesis H1: Levels of intestinal inflammation will be substantially higher in Zimbabweans living in rural areas and low-resource settings (i.e. high-density areas) compared to Zimbabwean and Swiss individuals living in high-resource settings.

Hypothesis H2: Bottlenecks and blooms of bacterial strains are less frequent in healthy participants than in inflammatory bowel disease (IBD) patients and bacterial strains will have lower mutation rates in healthy patients when compared to strains from IBD subjects (partner study: BASEC 2021-00871).

Hypothesis H3: Longitudinal changes of the faecal microbiome of healthy Swiss individuals differ systematically compared to longitudinal changes of the faecal microbiome of Swiss UC patients with active disease (partner study: BASEC 2022-02008).

Hypothesis H4: The HRV of healthy Swiss individuals differ systematically from HRV of Swiss IBD patients and can be associated with differentially abundant bacterial taxa (partner study: BASEC 2022-02008).

Objective:

This study investigates the relationship between lifestyle, gut bacteria, and diseases such as colorectal cancer and inflammatory bowel diseases (IBD). The investigators aim to understand how the gut microbiome, influenced by different environments, impacts disease development. Our research focuses on healthy Swiss individuals as a control group for ongoing projects.

Primary hypotheses:

Since data from this study will be used as control data for four studies, four primary hypothesis will be defined.

Hypothesis H1: Levels of intestinal inflammation will be substantially higher in Zimbabweans living in rural areas and low-resource settings (i.e. high-density areas) compared to Zimbabwean and Swiss individuals living in high-resource settings.

Hypothesis H2: Bottlenecks and blooms of bacterial strains are less frequent in healthy participants than in IBD patients and bacterial strains will have lower mutation rates in healthy patients when compared to IBD subjects (partner study: BASEC 2021-00871).

Hypothesis H3: Longitudinal changes of the faecal microbiome of healthy Swiss individuals differ systematically compared to longitudinal changes of the faecal microbiome of Swiss UC patients with active disease (partner study: BASEC 2022-02008).

Hypothesis H4: The heart rate variability (HRV) of healthy Swiss individuals differ systematically from HRV of Swiss IBD patients and can be associated with differentially abundant bacterial taxa (partner study: BASEC 2022-02008).

Secondary hypotheses Hypothesis H5: The faecal microbiome composition of healthy Swiss individuals differs systematically from the faecal microbiome composition of healthy Zimbabweans. (O1)

Hypothesis H6: The faecal microbiome composition of healthy Swiss individuals differs systematically from the faecal microbiome of Swiss UC patients experiencing a disease flare.

Hypothesis H7: The faecal microbiome composition of healthy Swiss individuals differs systematically from the faecal microbiome of Swiss UC patients after achieving disease remission.

Hypothesis H8: The faecal microbiome composition of healthy Swiss without symptoms of irritable bowel syndrome (Rome IV criteria) differs systematically from the faecal microbiome of healthy Swiss with symptoms of irritable bowel syndrome.

Design:

Observational cohort study with 200 healthy Swiss participants. Participants are followed-up during one year. During the study, 12 faecal samples, voluntary blood samples, and comprehensive data are collected from each participant. Assessed data include clinical assessments, detailed socio-economic information and voluntary heart rate variability (HRV) measurements. The study's longitudinal approach comprises 12 defined follow-ups at days 0, 3, 5, and 7; weeks 2, 3, 4, 8, and 12; and months 6, 9, and 12. The faecal samples will be collected by the participants at home with provided vials. In addition, each faecal sample is accompanied by a follow-up questionnaire to filled out by the patient. The questionnaires focus on gastrointestinal symptoms, fatigue, socio-economic variables, emotional well-being, five factor model (personality) assessment and type D personality, and a simple dietary assessment covering a 24-hour period. Participants will mail the stool vials and questionnaires, using a provided envelope, to Inselspital Bern via the Swiss postal service. Blood samples will be acquired only from a subset of the participants primarily at enrolment.

Recruitment:

Primarily at the Department of Visceral Surgery and Medicine of the University Hospital Bern (Inselspital Bern), and through outreach to the general population.

Eligibility Criteria:
Inclusion Criteria:

* Signed informed consent
* Age 18-90 years
* General ability to give consent for study inclusion, understand and follow study procedures
* No current or past diagnosis of IBD or colorectal carcinoma
* No current medical complaints typical for IBD or other severe intestinal diseases (e.g. Diarrhea, severe constipation, abdominal pain, blood in stool, weight loss). Minor symptoms, (not impairing daily activities) are permitted.
* No other current relevant gastrointestinal disease or condition plausibly interfering with microbiota assessment according to the discretion of the study physician.

Exclusion Criteria:

* All patients with recent acute gastrointestinal disease (e.g., confirmed infectious diarrhea) within the last month or relevant intestinal symptoms (impairing daily activities).
* Use of antibiotics within the last 3 months.
* Current pouch or ileostomy/ colostomy.
* Severe medical, surgical, or psychiatric comorbidities interfering with study procedure according to the judgement of the investigator (patients with comorbidities that would not interfere with the primary endpoints I-III but don't allow the assessment of HRV according to the judgement of the investigator (e.g. heart diseases) will be included in the study but the HRV will not be assessed).
* Participation in an interfering clinical study.