To be included in this study, participants must:

• Sign a consent form;
• Be older 18 or older and 90 or younger;
• Have diarrhea, at least 3 times during one day, or 200 mL or liquid stool if using a rectal device;
• Test positive for Clostridium difficile;
• If female, must not be pregnant or nursing and take appropriate measures to not get pregnant during the study.

Participants will not be allowed into the study if they:

• Have toxic megacolon and/or known small bowel ileus;
• Have received treatment with intravenous immune globulin (IVIG)within the past 30 days;
• Have received treatment with a fecal transplant within 7 days, and/or if the doctor anticipates to give the participant a fecal transplant during the study;
• Have received a certain amount of antibacterial therapy specific for current CDAD, unless it is not working;
• Have received an investigational vaccine against C. difficile;
• Have received an investigational product containing monoclonal antibodies against toxin A or B within 180 days;
• Had more than 2 episodes of CDAD within 90 days;
• Had major gastrointestinal (GI) surgery (i.e. significant bowel resection) within 3 months(this does not include appendectomy or cholecystectomy);
• Have history of prior inflammatory bowel disease: ulcerative colitis, Crohn's disease, or microscopic colitis;
• Are unable to discontinue loperamide, diphenoxylate/atropine, or cholestyramine during the duration of the study;
• Are unable to discontinue opiate treatment unless on a stable dose;
• Has known positive stool cultures for other enteropathogens including but not limited to Salmonella, Shigella, and Campylobacter;
• Had stool studies positive for pathogenic ova and/or parasites;
• Have an intolerance or hypersensitivity to daptomycin and/or vancomycin;
• Have life-threatening illness at the time of enrollment;
• Have poor concurrent medical risks that in the opinion of the Investigator the participant should not enroll;
• Have received an investigational drug or participated in any experimental procedure within 1 month;
• Have HIV, a CD4 <200 cells/mm3 within 6 months of start of study therapy;
• Anticipate that certain antibacterial therapy for a non-CDAD infection will be required for >7 days;
• Are unable to discontinue Saccharomyces or similar probiotic;
• Are on a concurrent intensive induction chemotherapy, radiotherapy, or biologic treatment for active malignancy;
• Are unable to comply with the protocol requirements;
• Have any condition that, in the opinion of the Investigator, might interfere;
• Are not expected to live for less than 8 weeks.