The Clostridioides Difficile Trial of REC-3964

Key Inclusion Criteria: * Be 18 years of age or older with Clostridioides difficile infection (CDI) diarrhea associated with a positive stool test for C. difficile toxin\[s\] prior to the preceding curative treatment. * The CDI episode, severe or otherwise, must have resolved after receiving vancomycin with a standard duration of treatment. The participant must be randomized within 2 days of completing the preceding curative treatment. * Have high risk for rCDI (a recurrent CDI episode within the last 6 months, age ≥65 years, immunocompromised state, or severe CDI with resolution prior to enrollment into the study). Key Exclusion Criteria: * Have an active, symptomatic, chronic diarrheal illness from other causes, such as ulcerative colitis or Crohn's disease. * Diarrhea that requires on-study treatment with agents that would confound the interpretation of the study results.