Inclusion Criteria:

• Male or female age 18-75 years.
• Have successfully completed a full course of a standard of care CDI antibiotic for a qualifying CDI episode (primary or recurrent) within 3 to 7 days of randomization:
  • Qualifying episode of CDI meets the following definition:
    • Positive stool C. difficile toxin (NAAT, EIA, CCTA, or equivalent test) as documented by study site; AND
    • History of ≥ 3 unformed (Bristol scores of 5, 6, or 7) bowel movements per day for at least 24 hours; AND
    • Received standard of care antibiotic treatment for CDI diagnosis.
• Prior to the first dose of study drug, completion of standard of care antibiotic therapy with oral vancomycin, metronidazole, or fidaxomicin for CDI with a treatment duration of 10 to 21 days.
• Clinical cure assessed and confirmed at screening and reconfirmed at Day 1 visit (randomization). Clinical cure must meet the following definition:
  • ≤ 2 unformed stools per day for at least 2 consecutive days and maintained through Day 1 without the need for further antibiotic therapy.
• Subject is able to begin treatment with study drug within 3 to 7 days following completion (i.e., last dose) of the CDI antibiotic course for the qualifying CDI episode.
• For female subjects of childbearing potential, be using an insertable, injectable, transdermal, or combination oral contraceptive approved and deemed highly effective by the United States Food and Drug Administration through 30 days after the last dose of study drug and have negative results on a serum pregnancy test at the Screening visit and a urine pregnancy test on Day 1.
  • NOTE: women who are surgically sterile or postmenopausal (i.e., no menses for at least 2 years or documented by follicle stimulating hormone) are also eligible to participate.
• For male subjects, vasectomized more than 6 months prior to study drug administration, or if non-vasectomized are required to practice reliable birth control methods (condom) or female partner of childbearing potential must use an effective birth control method through 30 days after the last dose of study drug.
• Understand the risks and benefits of participation and are able and willing to provide written informed consent.
• Willing and able to meet all study requirements including collection, handling, storage, and transport of stool samples to clinical site and attending all assessment visits and phone calls.

Exclusion Criteria:

• Body mass index ≥ 40.0 kg/m^2.
• Life expectancy of ≤ 12 months.
• Inpatient (in hospital or skilled nursing facility) at the time of randomization.
• Current (i.e., qualifying) CDI episode required admission to an Intensive Care Unit.
• Pregnant, breastfeeding, or seeking pregnancy while on study.
• Have, as determined by the Investigator, a history or clinical/laboratory manifestations of significant neurological, renal, hepatic, hematologic, cardiac, pulmonary, metabolic, endocrine, psychiatric, gastrointestinal disorders other than CDI (including infectious, ischemic, or immunological diseases), HIV, HBV, and/or HCV infection, or other condition that could interfere with the evaluation of safety or efficacy, or put the subject at risk of harm from study participation.
• Have an active malignancy of any type or history of a malignancy within past 5 years, except for treated basal cell or squamous cell carcinoma of the skin or carcinoma in situ of the cervix.
• Have an acute febrile illness (fever > 38°C [100.4°F]) at Day 1.
• Drug, alcohol, or substance dependence within the last 2 years.
• Anticipated hospital admission for any reason while on study.
• Any of the following laboratory results at Screening:
  • White blood cell count ≥ 15,000 cells/mm^3;
  • Absolute neutrophil count 1.8 mg/dL.
• Use of systemic antibiotic therapy for conditions other than CDI within 7 days of randomization or expectation to require antibiotic therapy for conditions other than CDI for 12 weeks following the first dose of study drug for Cohort A or 16 weeks following the first dose of study drug for Cohort B, including subtherapeutic doses of oral antibiotics (e.g., for rosacea).
• Have a known immunodeficiency disorder, including but not limited to:
  • An immunodeficiency disease;
  • Receiving, or plans to receive, treatment with systemic corticosteroids equivalent to > 10 mg prednisone per day;
  • Receiving, or plans to receive, myelosuppressive chemotherapy.
• Previous fecal transplant or live biotherapeutic product within 1 year of randomization.
• Treatment with bezlotoxumab (Zinplava™) for the qualifying CDI episode.
• Diagnosis of inflammatory bowel disease (including but not limited to: Crohn’s disease, ulcerative colitis, microscopic colitis), active irritable bowel syndrome [those with diarrhea predominant or alternating constipation and diarrhea] (in past 2 years based on Rome IV criteria and subject deemed not suitable for study by Investigator’s judgment), celiac disease not well controlled on gluten-free diet, active gastroparesis, toxic megacolon, pseudomembranous colitis, colostomy, intestinal resection (except appendectomy), ileus or short gut syndrome.
• History of chronic diarrhea.
• Intra-abdominal surgery, including laparoscopic procedures, within 8 weeks of Screening (appendectomy and cholecystectomy excluded).
• History of difficulty swallowing food or liquids.
• Taking antidiarrheal agents (e.g., loperamide) on a regular basis.
• Use of non-dietary probiotic supplements within 7 days of Day 1 or plan to use non-dietary probiotic supplements while on study through Week 12 in Cohort A and Week 16 in Cohort B.
• Known to have consumed fermented or other foods that may contain B. amyloliquefaciens (such as miso, soybean paste, or fermented rice- or locust bean-derived products) within 7 days prior to Day 1, or plan to consume them prior to Week 12 for Cohort A and prior to Week 16 for Cohort B.
• In the opinion of the Investigator, unable to comply with the study protocol.
• Participation in a clinical trial of an investigational drug or medical device within 30 days prior to the Screening visit.

Eligibility last updated 8/30/21. Questions regarding updates should be directed to the study team contact.