The Safety, Efficacy, and Tolerability of Microbial Ecosystem Therapeutic-2 in People With Major Depression

Inclusion Criteria: 1. Able to provide informed consent. 2. Not pregnant 3. Willing to participate in follow up as part of the study 4. Diagnosis of Major Depressive Disorder (MDD) by the Mini-International Neuropsychiatric Interview (MINI) 5. Current depressive episode with a Montgomery-Asberg Depression Rating Scale (MADRS) score of ≥15. 6. Able to understand and comply with the requirements of the study 7. Able to provide stool, urine, and blood samples. 8. Those who do not choose to use antidepressants for moderate-severe depression. Exclusion Criteria: 1. History of chronic diarrhea 2. Need for regular use of agents that affect gastro-intestinal (GI) motility (narcotics such as codeine or morphine, agents such as loperamide or metoclopramide) 3. Colostomy 4. Elective surgery that will require preoperative antibiotics planned within 6 months of enrolment 5. History of bariatric surgery. 6. Pregnant, breastfeeding, or planning to get pregnant in the next 6 months 7. Any condition for which, in the opinion of the investigator, the participant should be excluded from the study. 8. Current use of any antidepressant/antianxiety drug (eligible to participate after a 4-week washout period) 9. More than three depressive episodes throughout lifetime 10. Having failed an anti-depressant treatment during current depressive episode 11. Use of any antibiotic drug in the past 4 weeks (may be eligible to participate after a 1-month washout period) 12. History of alcohol or substance dependence in the past 6 months 13. Daily use of probiotic product in the past 2 weeks (may be eligible to participate after a 2-week washout period) 14. Use of any type of laxative in the last 2 weeks. 15. Consumption of products fortified in probiotics (may be eligible to participate after a 2-week washout period) 16. High suicidal risk, as measured by MADRS item 10 score more than 3 17. Current psychotic symptoms 18. Bipolar Depression 19. History of epilepsy or uncontrolled seizures 20. Immunodeficiency (immuno-compromised and immuno-suppressed participants; e.g. acquired immune deficiency syndrome \[AIDS\], lymphoma, participants undergoing long-term corticosteroid treatment, chemotherapy and allograft participants) 21. Unstable medical conditions or serious diseases/conditions (e.g. cancer, cardiovascular, renal, lung, diabetes, psychiatric illness, bleeding disorders, etc.) 22. The use of natural health products (NHP); e.g. St. John's Wort, passion flower, etc.) that affect depression 23. History of Electroconvulsive therapy (ECT)