125 mg Vancomycin over-encapsulated capsule administered orally, four times daily for a daily total dose of 500 mg, for 10 days

Placebo for Surotomycin over-encapsulated tablet administered orally, twice daily for 10 days

An AE is any untoward medical occurrence in a participant administered a pharmaceutical product that does not necessarily have to have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medicinal product, whether or not related to the medicinal product. AEs may be new events or may be pre-existing conditions that have become aggravated or have worsened in severity or frequency; or may be clinically significant changes from baseline in physical examination, laboratory tests, or other diagnostic investigation (e.g. laboratory results, x-ray findings).

Sustained clinical response at the end of study was achieved by participants who had a clinical outcome of cure at the end of treatment (Days 40-50) and did not experience a recurrence of CDAD, did not die, were not lost to follow-up, and did not have end of study visit prior to Day 40. The estimated adjusted percentage was a weighted average across all strata, constructed using MRc stratum weights.

Sustained clinical response at Day 24 was defined as participants who had a clinical outcome of cure at Day 24, who did not experience a recurrence of CDAD, did not die, were not lost to follow-up. Only the first failure event was counted per participant. The estimated adjusted percentage was a weighted average across all strata, constructed using MRc stratum weights.

Participants with recurrences were defined as those who were cured at the end of therapy and had a recurrence or were lost to follow-up, died or had a Day 40 -50 contact prior to Day 40. The estimated adjusted percentage was a weighted average across all strata, constructed using MRc stratum weights.

Time to resolution of diarrhea with =< 2 unformed bowel movements (UBM) per 24-hour period was calculated as the date/time of last UBM minus the date/time of the first dose of study drug.

Time to reappearance of diarrhea with >= 3 UBM per 24-hour period was calculated as the last date/time of study drug dose to the date/time of first reappearance of 3 or more UBMs among participants who were cured at end of treatment.

Clinical response corresponded to a clinical outcome of cure at the end of treatment, and was achieved by participants with infections deemed to be caused by the C. difficile BI/NAP1/027 strain at baseline, who did not fail treatment, did not die, or were not lost to follow-up at the end of treatment. The estimated adjusted percentage was a weighted average across all strata, constructed using MRc stratum weights.

Clinical response corresponded to a clinical outcome of cure at the end of treatment, and was achieved by participants who did not fail treatment, did not die, or were not lost to follow-up at the end of treatment. The estimated adjusted percentage was a weighted average across all strata, constructed using MRc stratum weights.

Sustained clinical response at the end of study was achieved by participants with infections deemed to be caused by the C. difficile BI/NAP1/027 strain at baseline, who had a clinical outcome of cure at the end of treatment (Day 13) and did not experience a recurrence of CDAD, did not die, were not lost to follow-up, and did not have end of study visit prior to Day 40. The estimated adjusted percentage was a weighted average across all strata, constructed using MRc stratum weights.

Sustained clinical response at the end of study was achieved by participants who had a clinical outcome of cure at the end of treatment (Days 40-50) and did not experience a recurrence of CDAD, did not die, were not lost to follow-up, and did not have end of study visit prior to Day 40. Only the first failure event per participant was counted. The estimated adjusted percentage was a weighted average across all strata, constructed using MRc stratum weights.

Total of all reporting groups

Number of participants <75 or >=75 years old at First Dose

Randomized participants with Confirmed CDAD

Number of participants with previous episodes of CDAD

Randomized participants with Confirmed CDAD evaluated for previous episodes of CDAD

Number of participants with the BI/NAP1/027 Strain

Randomized participants with Confirmed CDAD evaluated for BI/NAP1/027 Strain

Clinical response over time as measured by those without treatment failure, recurrence, death, or lost to follow-up, measured as the number of participants without failure events (survivors) through the end of therapy (reported for Day 14) and from end of therapy to Day 40 (reported for Day 41).

The mMITT population consisting of all randomized participants who had a confirmed diagnosis of CDAD regardless of whether they received any amount of study drug, based on the treatment to which they were randomized

Sustained clinical response at the end of study was achieved by participants who had a clinical outcome of cure at the end of treatment (Days 40-50) and did not experience a recurrence of CDAD, did not die, were not lost to follow-up, and did not have end of study visit prior to Day 40. The estimated adjusted percentage was a weighted average across all strata, constructed using MRc stratum weights.

The mMITT population consisting of all randomized participants who had a confirmed diagnosis of CDAD regardless of whether they received any amount of study drug, based on the treatment to which they were randomized.

An AE is any untoward medical occurrence in a participant administered a pharmaceutical product that does not necessarily have to have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medicinal product, whether or not related to the medicinal product. AEs may be new events or may be pre-existing conditions that have become aggravated or have worsened in severity or frequency; or may be clinically significant changes from baseline in physical examination, laboratory tests, or other diagnostic investigation (e.g. laboratory results, x-ray findings).

All randomized participants who received any amount of study drug

A SAE is any adverse experience occurring at any dose that results in any of the following outcomes: death; a life-threatening experience, referring to a situation in which the participant was at risk of death at the time of the event, requires in-patient hospitalization or prolongation of existing hospitalization; results in persistent or significant disability or incapacity; is a congenital anomaly or birth defect; or is considered to be an important medical event.

All randomized participants who received any amount of study drug

An AE is any untoward medical occurrence in a participant administered a pharmaceutical product that does not necessarily have to have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medicinal product, whether or not related to the medicinal product. AEs may be new events or may be pre-existing conditions that have become aggravated or have worsened in severity or frequency; or may be clinically significant changes from baseline in physical examination, laboratory tests, or other diagnostic investigation (e.g. laboratory results, x-ray findings).

All randomized participants who received any amount of study drug

Sustained clinical response at Day 24 was defined as participants who had a clinical outcome of cure at Day 24, who did not experience a recurrence of CDAD, did not die, were not lost to follow-up. Only the first failure event was counted per participant. The estimated adjusted percentage was a weighted average across all strata, constructed using MRc stratum weights.

The mMITT population consisting of all randomized participants who had a confirmed diagnosis of CDAD regardless of whether they received any amount of study drug, based on the treatment to which they were randomized.

Participants with recurrences were defined as those who were cured at the end of therapy and had a recurrence or were lost to follow-up, died or had a Day 40 -50 contact prior to Day 40. The estimated adjusted percentage was a weighted average across all strata, constructed using MRc stratum weights.

The mMITT population consisting of all randomized participants who had a confirmed diagnosis of CDAD regardless of whether they received any amount of study drug, based on the treatment to which they were randomized.

Time to resolution of diarrhea with =< 2 unformed bowel movements (UBM) per 24-hour period was calculated as the date/time of last UBM minus the date/time of the first dose of study drug.

The mMITT population consisting of all randomized participants who had a confirmed diagnosis of CDAD regardless of whether they received any amount of study drug, based on the treatment to which they were randomized

Time to reappearance of diarrhea with >= 3 UBM per 24-hour period was calculated as the last date/time of study drug dose to the date/time of first reappearance of 3 or more UBMs among participants who were cured at end of treatment.

The mMITT population consisting of all randomized participants who had a confirmed diagnosis of CDAD regardless of whether they received any amount of study drug, based on the treatment to which they were randomized; and were cured at end of treatment.

Clinical response corresponded to a clinical outcome of cure at the end of treatment, and was achieved by participants with infections deemed to be caused by the C. difficile BI/NAP1/027 strain at baseline, who did not fail treatment, did not die, or were not lost to follow-up at the end of treatment. The estimated adjusted percentage was a weighted average across all strata, constructed using MRc stratum weights.

Randomized participants who had a confirmed diagnosis of CDAD regardless of whether they received any amount of study drug, based on the treatment to which they were randomized; and with infections deemed to be caused by the C. difficile BI/NAP1/027 strain at baseline.

Clinical response corresponded to a clinical outcome of cure at the end of treatment, and was achieved by participants who did not fail treatment, did not die, or were not lost to follow-up at the end of treatment. The estimated adjusted percentage was a weighted average across all strata, constructed using MRc stratum weights.

The population analyzed is the Per Protocol 1 (PP1) population composed of participants from the mMITT population, according to the actual treatment they received; without any protocol deviations from enrollment through 2 days after end of treatment, which could affect the efficacy conclusions.

Sustained clinical response at the end of study was achieved by participants with infections deemed to be caused by the C. difficile BI/NAP1/027 strain at baseline, who had a clinical outcome of cure at the end of treatment (Day 13) and did not experience a recurrence of CDAD, did not die, were not lost to follow-up, and did not have end of study visit prior to Day 40. The estimated adjusted percentage was a weighted average across all strata, constructed using MRc stratum weights.

All randomized participants who had a confirmed diagnosis of CDAD regardless of whether they received any amount of study drug, based on the treatment to which they were randomized; and with infections deemed to be caused by the C. difficile BI/NAP1/027 strain at baseline

Sustained clinical response at the end of study was achieved by participants who had a clinical outcome of cure at the end of treatment (Days 40-50) and did not experience a recurrence of CDAD, did not die, were not lost to follow-up, and did not have end of study visit prior to Day 40. Only the first failure event per participant was counted. The estimated adjusted percentage was a weighted average across all strata, constructed using MRc stratum weights.

The Per Protocol 2 (PP2) population composed of cures and failures from the PP1 population. Additionally, to be included in the PP2 population, PP1 participants who were cured at end of treatment must not have had any protocol deviations which could affect the assessment of recurrence and have had follow-up contact through at least Day 40.

125 mg Vancomycin over-encapsulated capsule administered orally, four times daily for a daily total dose of 500 mg, for 10 days