This study will evaluate efficacy and safety information about RBX2660 for the treatment of recurrent Clostridium difficile infection (CDI), and will compare the efficacy of one treatment with RBX2660 versus antibiotic-treated historical controls. Enrolled subjects will receive one treatment consisting of two doses of RBX2660 (microbiota suspension).

This is a prospective, multicenter, open-label study assessing the efficacy and safety of RBX2660 as an adjunct to antibiotics for the treatment of recurrent CDI. Efficacy of RBX2660, measured by the recurrence-free rate of CDI diarrhea without the need for retreatment with C. difficile anti-infective therapy or fecal transplant through 56 days after completion of study treatment with RBX2660, will be evaluated by comparing the recurrence-free rate observed in the study population to the recurrence-free rate identified from antibiotic-treated historical controls.

Patients who have had either a) at least two recurrences after a primary episode (i.e., at least three episodes) and have completed at least two rounds of standard-of-care oral antibiotics or b) have had at least two episodes of severe CDI resulting in hospitalization may be eligible to participate in the study. Study visits are 1- and 8-weeks after treatment with additional follow-up assessments at 3,6,12, and 24 months post treatment.

Inclusion Criteria:

• ≥ 18 years old.
• Medical record documentation of recurrent CDI including a positive C. difficile test within 60 days prior to enrollment and 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 CDI diarrhea despite being on a course of antibiotics prescribed for CDI treatment.
• Requires continuous antibiotic therapy for a condition other than CDI.
• Previous successful (resolution of CDI diarrhea) fecal transplant for recurrent CDI < 6 months prior to study enrollment.
• Previous unsuccessful (recurrent CDI diarrhea was unresolved) fecal transplant.
• Previous treatment with RBX2660.
• Diagnosis of inflammatory bowel disease (IBD), e.g., ulcerative colitis, Crohn's disease, or microscopic colitis.
• Diagnosis of irritable bowel syndrome (IBS) as determined by Rome III criteria.
• History of chronic diarrhea.
• History of celiac disease.
• Disease symptoms caused by a confirmed intestinal pathogen other than C. difficile.
• Colostomy.
• Planned surgery requiring perioperative antibiotics within 3 months of study enrollment.
• Life expectancy of < 12 months.
• Compromised immune system