Inclusion Criteria:

• Ability to provide written informed consent.
• Men or women 18 years of age or older.
• Previously enrolled in PRISM3, had a CDI recurrence within 8 weeks of receiving CP101 or placebo, and have completed their PRISM3 end of study visit. The following qualifications must be met:
  • The CDI recurrence must have met the PRISM3 protocol definition of:
    • Diarrhea (> 3 unformed stools [Bristol Stool Scale score of 6 or 7] per day) for 2 or more consecutive days;
    • A stool specimen testing positive for Clostridium difficile (C. difficile) by the PRISM3 testing algorithm; and
    • Requiring a course of standard-of-care CDI antibiotics.; AND
  • Subject has received a course of standard-of-care CDI antibiotics for the most recent CDI episode (for 10-42 days, with exact duration, antibiotic type, and dose at the discretion of the Investigator); AND
  • Subject has had an adequate clinical response, defined as ≤ 3 unformed stools in 24 hours for 2 or more consecutive days during standard-of-care CDI antibiotics prior to Treatment.
• Willingness to abstain from consuming non-dietary probiotics through Week 8 after Treatment
• Women must fulfill at least 1 of the following criteria:
  • Post-menopausal, defined as amenorrhea ≥ 1 year;
  • Surgically sterile: hysterectomy, bilateral oophorectomy, or tubal ligation; or
  • Abstinent or willing to use adequate contraception from Screening through the Week 24 visit.
• Deemed to have life expectancy of 8 weeks or greater.

Exclusion Criteria:

• Admitted to, or expected to be admitted to, an intensive care unit for any medical reason.
  • NOTE: Residents of long term care facilities, such as nursing homes and rehabilitation centers, are eligible for study entry.
  • NOTE: Patient visits to clinics, urgent care centers, acute care hospitals, or emergency departments are allowed; however, subject must be an outpatient prior to Treatment.
• Stools known to be positive for ova and/or parasite(s), or other enteric pathogens (e.g., Salmonella, Shigella, and/or Campylobacter) within 28 days prior to Screening.
• Inability to ingest capsules (e.g., severe nausea, vomiting, and/or dysphagia).
• Known or suspected toxic megacolon and/or known small bowel ileus.
• Prior history, evidence, or diagnosis of inflammatory bowel disease (e.g., Crohn’s disease, ulcerative colitis, indeterminate colitis, or microscopic colitis).
• Recent diagnosis (< 6 months prior to Screening) of diarrhea-predominant irritable bowel syndrome (post-infection or not related to an enteric infection). Subjects with diarrhea-predominant irritable bowel syndrome ≥ 6 months prior to Screening may be treated after consultation with the Medical Monitor.
• Current diagnosis of chronic diarrheal illness with pre-CDI baseline diarrhea (≥ 3 loose stools in a 24-hour period). This includes but is not limited to celiac disease, bile salt diarrhea, chronic pancreatitis, and short gut syndrome.
• Past administration of bezlotoxumab (Zinplava™), or past enrollment in a C. difficile vaccine study within 12 months of Treatment.
• Initiation of any systemic cancer treatment (e.g. chemotherapy, radiotherapy, biologic, other) for active malignancy that is planned 8 weeks prior to Treatment or during the 8 weeks following Treatment. Subjects on maintenance treatment for malignancy may be treated after consultation with the Medical Monitor.
• Initiation or escalation of immunosuppressive agents, at the discretion of the Investigator, for any condition during the 8 weeks prior to Treatment or planned during the 8 weeks following Treatment. Subjects on stable immunosuppressive agents or short-courses may be treated after consultation with the Medical Monitor.
  • NOTE: Solid organ transplant recipients are excluded.
• Compromised immune system, including, but not limited to, a known history of human immunodeficiency virus infection and a cluster of differentiation 4 count that is unknown or documented to be < 200 cells/mm3 within the last year, or an acquired immunodeficiency syndrome-defining illness; or at the discretion of the Investigator.
• Fecal transplant for any condition, regardless of route of administration in the last year or plans to undergo during the study.
  • NOTE: CP101 use in PRISM3 is not exclusionary.
• Major intra-abdominal surgery (e.g., bowel resection) within the past 60 days prior to Screening (excluding appendectomy or cholecystectomy), history of total colectomy/ileostomy and/or planned invasive surgery/hospitalization during the study.
  • NOTE: Subjects with history of bariatric surgery may be treated after consultation with the Medical Monitor.
• Use of a systemic antibiotic for any condition (other than CDI therapy for the current recurrence) during the Screening period, or any anticipated use of a systemic antibiotic for any condition other than CDI during the study for 8 weeks after Treatment. This includes subjects who have a known medical procedure that requires antibiotic prophylaxis (e.g., elective surgical procedure or dental procedure requiring prophylactic antibiotics) scheduled during the study.
• Unable to discontinue drugs that are specifically used as antiperistaltic agents (e.g., intended to control diarrhea, including but not limited to loperamide, diphenoxylate-atropine, or opioids).
  • NOTE: Opioids prescribed for chronic pain or other indications are allowed if stable dose or decreasing dose during the course of the study. Changes in regimen should be discussed with the Medical Monitor.
• Active drug, chemical, or alcohol dependency as determined by the Investigator through history or optional toxicology screen.
• Enrollment in any other investigational drug or device study within 30 days prior to Treatment (Day 1) or within 5 half-lives of the last dose of the previous investigational compound, whichever is longer.
  • NOTE: CP101 use in PRISM3 is not exclusionary.
• Pregnant, breast-feeding, or considering becoming pregnant during the study.
• Clinically significant abnormal laboratory values including, but not limited to, white blood cell count ≥ 15 x 109, laboratory evidence of acute kidney injury, or absolute neutrophil count of < 1 x 109 neutrophils at Screening.
• Any acute or chronic medical comorbidity, psychiatric, social, or other circumstances that, in the opinion of the Investigator, may interfere with study compliance, completion, or accurate assessment of study outcomes/safety.

• NOTE: To be eligible for Treatment, the above listed Inclusion/Exclusion Criteria as well as the following additional Inclusion Criteria must be satisfied:

Treatment (Day 1) Inclusion Criteria:

• An outpatient prior to Treatment.
  • NOTE: Subject may be enrolled while an inpatient in an acute care facility, but must be discharged prior to Treatment on Day 1. Subjects residing in an assisted living center, long-term care facility, or rehabilitation center may be treated.
• Has received a course of standard-of-care CDI antibiotics for the most recent CDI episode (for 10-42 days, with exact duration, antibiotic type, and dose at the discretion of the Investigator).
• Has an adequate clinical response defined as ≤ 3 unformed stools in 24 hours for 2 or more consecutive days during standard-of-care CDI antibiotics prior to Treatment.
• Subject has completed a washout (i.e., a minimum of 2 and a maximum of 6 days after cessation of standard-of-care CDI antibiotics). If the subject experiences diarrhea for 2 or more consecutive days during the washout period, the Investigator should contact the Medical Monitor.