This is the first prospective, multi-center, double-blinded, randomized controlled study of a microbiota suspension derived from intestinal microbes. Patients who have had at least two recurrences of C. difficile infection (CDI) after a primary episode and have completed at least two rounds of standard-of-care oral antibiotic therapy or have had at least two episodes of severe CDI resulting in hospitalization may be eligible for the study. Patients whose CDI returns in less than 8 weeks after the last assigned study treatment may be eligible to receive up to 2 treatments with RBX2660 in the open-label portion of the study.

This is the first prospective, multi-center, double-blinded, randomized controlled study of a microbiota suspension derived from intestinal microbes. The primary assessments for this study are (i) efficacy of RBX2660 compared to placebo at 8 weeks and (ii) safety via assessment of adverse events. Study visits are at 1-, 4- and 8-weeks after treatment with additional follow-up at 3, 6 12 and 24 months post treatment. Patients who have had at least two recurrences of C. difficile infection (CDI) after a primary episode and have completed at least two rounds of standard-of-care oral antibiotic therapy or have had at least two episodes of severe CDI resulting in hospitalization may be eligible for the study. Patients whose CDI returns in less than 8 weeks after the last assigned study treatment may be eligible to receive up to 2 treatments with RBX2660 in the open-label portion of the study.

Inclusion Criteria:

• ≥ 18 years
• Medical record documentation of recurrent CDI either: a) at least two recurrences after a primary episode and has completed at least two rounds of standard-of-care oral antibiotic therapy or b) has had at least two episodes of severe CDI resulting in hospitalization.
• Documented history that the subject's recurrent CDI is controlled while on antibiotics even if the subject is not currently on antibiotics.
• A positive stool test for the presence of C. difficile within 60 days prior to enrollment.

Exclusion Criteria:

• A known history of continued C. difficile diarrhea while taking on a course of antibiotics prescribed for CDI treatment.
• Requires antibiotic therapy for a condition other than recurrent CDI.
• Previous fecal transplant prior to study enrollment.
• History of inflammatory bowel disease (IBD), e.g., ulcerative colitis, Crohn's disease, or microscopic colitis.
• History of irritable bowel syndrome (IBS).
• History of chronic diarrhea.
• History of celiac disease.
• Colostomy.
• Planned surgery requiring perioperative antibiotics within 6 months of study enrollment.
• Life expectancy of < 12 months.
• Compromised immune system.