Clinical Research Directory

Inclusion Criteria: 1. Age 18 to 65 years inclusive at the time of signing the informed consent. 2. Diagnosis of IBS-D according to the Rome IV criteria (Lacy 2017). 3. At least 1 of the following measures of microbiome dysfunction: 1. Primary bile acid proportion ≥ 12% in stool samples, or 2. Positive hydrogen breath test (with either glucose or lactulose substrate) (Rezaie 2017) 4. Normal C-reactive protein level 5. Gallbladder intact 6. Willing to use appropriate contraception during the treatment period and for one week after the last study visit. * Male participants with partners who are women of childbearing potential (WOCBP): Appropriate contraception includes condoms or other means considered adequate by the responsible Investigator. * Female participants who are WOCBP: Appropriate contraception includes condoms, an intrauterine device, hormonal contraception, or other means considered adequate by the responsible Investigator. 7. Capable of giving signed informed consent as described in Appendix 1, which includes compliance with the requirements and restrictions listed in the informed consent form and in this protocol. 8. Able to tolerate the planned course of antibiotics, EGD, and colonoscopy with bowel lavage. Exclusion Criteria: 1. Inflammatory bowel disease 2. Untreated enteric infections 3. History of gastrointestinal (GI) surgery: All participants with GI surgeries below the pylorus will be excluded from this study. This includes participants with a history of colectomy, segmental colonic resection, and small bowel resections. 4. Documented severe gastroparesis 5. Active intestinal obstruction 6. Dysphagia (oropharyngeal, esophageal, functional, or neuromuscular) 7. History of recurrent aspiration episodes 8. Any conditions associated with a high risk of bleeding, including but not limited to coagulopathy/bleeding disorder, severe liver disease, active or recent GI bleeding, or recent abdominal or other GI surgery 9. Active diagnosis of major depressive disorder 10. Severe immunodeficiency, inherited or acquired (e.g., human immunodeficiency virus, active chemotherapy or immunosuppressive medications \[including steroids, biologic therapy, or bone marrow suppressive agent\], or radiation therapy) 11. Any other significant medical condition that could confound or interfere with evaluation of safety or tolerability or prevent compliance with the study protocol at the discretion of the Investigator 12. Active antibiotic use (except protocol-specified antibiotics) 13. Active treatment with high levels of immunosuppressive therapies (active chemotherapy or immunosuppressive medications \[including steroids, biologic therapies, or bone marrow suppressive agents\], or radiation therapy) 14. Active anticoagulant or antiplatelet therapy, or use of other medications associated with a high risk of bleeding within 48 hours prior to endoscopy on Day 1 15. Use of a probiotic within one month prior to dosing of MITI-001 on Day 1 16. Simultaneous participation in another interventional clinical trial 17. Renal insufficiency (estimated glomerular filtration rate \< 50 mL/min) 18. Absolute neutrophil count \< 1000 μL, platelet count \< 50 × 109/L, or hemoglobin level \< 6.5 g/dL 19. Pregnant, breastfeeding, or planning pregnancy during the study period 20. Active drug or alcohol use disorder 21. Known allergy or anaphylaxis to vancomycin, metronidazole, ciprofloxacin, or polyethylene glycol 22. Inability to comply with research requirements