Inclusion Criteria:  Patient has an established diagnosis of ulcerative colitis for at least 3 months prior to Screening Patient has active mild to moderate ulcerative colitis at Visit 2 Patient is taking at least one of the following oral medication: 5-ASA, Corticosteroids, Immunomodulators  Exclusion Criteria:  Patient has a possible or confirmed diagnosis of Crohn's Disease or other forms of inflammatory bowel disorders Patient has a persistent fever of ≥ 38.3°C Patient has current signs or symptoms of infection Patient has any immunosuppressant condition Patient has a known malignancy within 5 years prior to Screening Patient has a known allergy or intolerance to vancomycin Patient has any contraindication for use of vancomycin Patient who has a medical history of drug abuse or alcohol abuse Patient who, in the opinion of the Investigator, has a clinically significant co-morbid disease Patient has hepatic failure Patient is pregnant or plans a pregnancy within the study period Patient has no previous history of treatment for ulcerative colitis (treatment-naïve patient) Patient has ongoing or failed treatment for ulcerative colitis with calcineurin inhibitor Patient has received biologic medication Patient has received antibiotics within 4 weeks prior to Visit 2 Patient is unable to stop previous antibiotics treatment during study period Patient has received probiotics within 2 weeks prior to Visit 2 Patient with history of major surgery in any region of the gastrointestinal tract Patient has received any investigational product or participated in another clinical trial Patient has a stool culture or other examination positive for an enteric pathogen Patient tests positive for CMV by PCR test at Screening Patient tests positive for HIV at Screening Exclusion criteria based on results of Hepatitis B at Screening Exclusion criteria based on results of Hepatitis C at Screening