Changes in Microbiota and Metabolomic Profile Between Rifaximin Responders and Non-responders In Diarrhoea-Predominant Irritable Bowel Syndrome
Condition: Irritable Bowel Syndrome With Diarrhea
MeSH terms: Irritable Bowel Syndrome; Syndrome; Diarrhea
Study type: Interventional
Phase: Phase 4

Summary: 
      Irritable Bowel Syndrome (IBS) carries a high prevalence worldwide and imposes substantial
      economic burden on patients, healthcare systems and society. In recent years, dysbiosis of
      the gut microbiota and bile acid (BA) malabsorption have been identified as putative
      pathophysiological mechanisms. Bile acid metabolism and gut microbiota are closely related.
      When patients with IBS-D were compared to healthy subjects, total levels of faecal BAs do not
      differ, but increased faecal primary BAs and reduced secondary BAs have been repeatedly
      observed in patients with IBS-D, suggesting abnormal BA deconjugation. Rifaximin, a
      non-absorbable antibiotic, has been shown in a recent meta-analysis to produce a therapeutic
      clinical gain compared to other treatment options for IBS, including placebo, paralleled by a
      high safety profile. It is also now known that changes in fecal microbiota have been observed
      in patients with IBS who have responded positively to Rifaximin. The relationship between
      microbiota changes, metabolomics changes after Rifaximin is unclear. There is emerging data
      to suggest duodenal dysbiosis as a putative pathophysiology, which in one study, clustered
      together with salivary microbiota than with fecal microbiota. However, the oral microbiome in
      patients with IBS has never been explored, which could possibly explain the downstream
      observations of duodenal and fecal dysbiosis. The investigators aim to assess the changes in
      metabolomic and microbiota profile after Rifaximin treatment, between responders and
      non-responders. The investigators will also explore the oral microbiome in IBS patients, and
      assess its relationship with fecal microbiome between responders and non-responders.
    

Detailed description: 
      The primary hypothesis of the study is that amongst responders to Rifaximin, fecal primary
      BAs will be significantly reduced, and faecal secondary BAs significantly increased after
      treatment.

      The secondary hypotheses include:

        1. Reduction in Escherichia and increase in Lactobacillus after treatment, as a possible
           mechanism to explain the increased deconjugation of primary BAs observed.

        2. Oral microbiome correlates with gut microbiome dysbiosis in IBS-D subjects.

        3. Rifaximin therapy alters both oral and gut microbiota, and that responders to Rifaximin
           harbour different microbiota compared to non-responders.

             1. Primary Objectives Primary Objective: To compare oral microbiome and fecal
                microbiome in IBS-D patients before and after Rifaximin, examining differences
                between responders and non-responders.

             2. Secondary Objectives Secondary objectives: To examine the differences between stool
                and salivary metabolomics, urinary metabolomics and serum immunomics and
                metabolomics, between responders and non-responders to Rifaximin in IBS-D subjects.

      Responders to Rifaximin will be defined as patients having a 50 point or more reduction in
      the IBS Symptom Severity Score (IBS-SSS) after treatment. This indicates that the patient has
      experienced a significant improvement in the reduction of symptoms. The IBS-SSS is a
      well-validated questionnaire that is patient-administered. This questionnaire will be
      administered at Day 0 and Day 14 of Rifaximin.

      Up to 50 subjects with Diarrhoea-predominant Irritable Bowel Syndrome (IBS-D) will be
      recruited from the National University Hospital Gastroenterology clinic and Singapore General
      Hospital Gastroenterology clinic. There will be subject restrictions on race, so as to limit
      variation due to inter-racial differences and ensure homogeneity in the subject population.

      Determination of Sample Size Adopted from the sample size calculation table for human
      microbiome studies by La Rosa (La Rosa et al. 2012), the study will require 15 subjects to
      have 80% power at p<0.05 significance level. To account for multiple testing, investigators
      will require at least 25 subjects for each category to have 90% power at p<0.01 significance
      level. The investigating team will be recruiting a total of 40 respondents and 40
      non-respondents from both NUH and SGH.

      Statistical and Analytical Plans Pair-wise comparison will be conducted between the 2 sample
      groups for differences in the microbiome. Concordance will be examined between the oral and
      fecal groups, both before and after treatment. Identified species will be examined for
      possible metabolic pathways based on their genetic profiles generated by the metagenomic
      analysis.

      Data Quality Assurance Demographics will be collected from the patient medical records. The
      oral conditions will be recorded in data collection form after oral examinations. The data
      collection form will be checked and signed off by PI. All the records will be entered twice
      into database by the delegated study team members to ensure accuracy of data.

      Data Entry and Storage Initial collection will be on paper-based data collection form. All
      subjects will be assigned a unique study subject code and the data collection form will be
      labelled with subject recruitment number. The de-identified data will be transferred into
      analysis software and kept on an encrypted flash drive kept by the delegated study team
      members. The data collection form will be put in lockable cabinet for 6 years after study
      completion, being accessed by study team only. De-identified data may be provided to a
      biostatistician for further analysis.

      Study Visits and Procedures This is a multi-centre open-label prospective cohort study.
      Recruited subjects will be patients who are newly diagnosed IBS-D, who undergo a two-week
      course of Rifaximin as indicated by their primary physician. Patients with symptomatic
      improvement (responders) after treatment will be compared to patients who do not improve
      (non-responders), based on a validated IBS Symptom Severity Score. As this is a cohort study,
      there will be no randomization or blinding. All patients will receive Rifaximin and no
      placebo will be used.

      The study will consist of the following phases:

      Visit 1: Screening The screening phase will include assessing eligibility based on the
      inclusion and exclusion criteria, obtaining informed consent, followed by a one-week symptom,
      bowel and 3-day dietary diary. All subjects will undergo further oral examination to
      determine oral status such as caries and periodontal status. This is to accurately evaluate
      the patient's baseline symptoms, bowel and dietary habits. Patients will be given a stool
      collection kit for collection of stool sample (10-20g) to be returned before or at the next
      visit.

      Visit 2: Enrolment and treatment (Day 1 Rifaximin) After the screening phase, patients will
      complete the IBS-SSS, and will be enrolled if a score of 300 or greater is obtained. Urine
      (50ml), saliva (5-10ml), 2 buccal swabs and blood samples (20ml) will be obtained during this
      visit as well.

      Patients will then initiate Rifaximin for two weeks. During these two weeks, patients will
      continue the symptom, bowel and 3-day dietary dairy, and also whether they have remembered to
      take their medication, and any side effects observed.

      Visit 3: Follow-up post-treatment (Day 14 Rifaximin) Patients will be asked to provide stool
      (10-20g), urine (50ml), saliva (5-10ml), 2 buccal swabs and blood samples (20ml) again at or
      1-week after Day 14, and repeat the IBS-SSS. The diaries will be collected, and compliance to
      medication will be verified.

      Subjects who discontinue the study early due to an AE will be followed until resolution or
      stabilization of the event.

      Visit 4: Review of symptoms 90 days after completing Rifaximin treatment. Patients will be
      asked to repeat the IBS-SSS. The symptom, bowel and 3-day dietary dairy will be collected and
      patients will be asked to provide stool (10-20g), urine (50ml), saliva (5-10ml), 2 buccal
      swabs and blood samples (20ml).
    

Intervention name(s): Rifaximin Oral Tablet
Intervention type(s): Drug
Intervention description(s): PO 550mg TDS for 2 weeks
Intervention MeSH terms: Rifaximin
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Rifaximin