The Safety and Efficacy of Fecal Microbiota Transplantation in a Population With Major Depressive Disorder

Inclusion Criteria: 1. Between 18-65 years of age: Participants should be at least 18 years old and not older than 65 years at the day of screening 2. Have a primary diagnosis of MDD according to the M.I.N.I. International Neuropsychiatric Interview (MINI)47 3. Medical history suggestive of Treatment Resistant Depression (TRD). (inadequate response to at least 2 approved antidepressants. at least one of which is in the current episode of depression)48 4. Have been on a current treatment with a approved antidepressant at an adequate dose for at least 8 weeks 5. A MADRS score of ≥ 19 at screening and visit 2 Additional Inclusion Criteria: \- Participants who will be included in the IBS-D cohort should have a confirmed diagnosis of IBS-D as indicated by the referring gastroenterologist. Exclusion Criteria: * 1\. Participant meets Diagnostic and Statistical Manual of Mental Disorders (DSM-5)1 Criteria for the following conditions according to the M.I.N.I: f) Substance Use Disorder within the last 3 months. \*(Criteria should include Alcohol and non-alcohol substances except Cannabis) g) Moderate or severe Substance use disorder for Cannabis use the last 3 months h) Active Anorexia Nervosa or Bulimia nervosa i) Schizophrenia or schizoaffective disorder j) Active suicidality 2. Regular intake of non-steroidal anti-inflammatory drugs, antibiotics, or iron supplements for medical purposes in the 3 months prior to study entry 3. Use of prebiotics or probiotics for medical purposes for more than 2 weeks within the last 3 months 4. Clinically diagnosed chronic gastrointestinal diseases (IBD, Crohn's disease, Ulcerative colitis, Celiac disease) 5. Conditions causing immune suppression 6. Not breastfeeding, pregnant or seeking to get pregnant during the course of this study. Be using an acceptable method of birth control (implants, injectable, combined oral contraceptives, IUDs, sexual abstinence or a vasectomized partner) 7. Reported allergy to Vancomycin or Nitazoxanide