Inclusion Criteria:

Eligible subjects must meet all of the following inclusion criteria:

• Willingness and ability to comply with all study requirements, to fully understand all elements of informed consent, and to provide written informed consent.
• Confirmed CDAD by ELISA toxin assay or cell test.
• Are currently receiving or have received standard antibiotic treatment for CDAD with oral/intravenous metronidazole and/or vancomycin for a minimum of 10 days per standard of care at the discretion of the study physician.
• Resolution of diarrhea to a maximum of 3 stools per day following completion of antibiotic therapy.
• Ability to tolerate fluids by mouth or by feeding tube.
• Have passage of stools.

Exclusion Criteria:

Subjects will not be eligible to participate in this study if any of the following exclusion criteria apply:

• Unable to provide informed consent.
• History of lactose intolerance.
• Cannot tolerate fluids by mouth or by feeding tube, or are judged by the attending physician unfit to receive fluids by mouth or by feeding tube.
• Have received an investigational drug within 4 weeks prior to study entry.
• Have underlying gastrointestinal tract disease characterized by diarrhea or unformed stools.
• Are currently receiving any antidiarrheal medications.
• Current use of an ileostomy or colostomy.
• History of milk allergy.
• Current use of Saccharomyces boulardii, Lactinex, or Culturelle preparations at start of study. (S. boulardii is a non-colonizing yeast species purported to support gastrointestinal tract function. It has been widely studied and used to help prevent post-antibiotic diarrhea.)
• Reside outside of the United States.
• Cannot speak or read English.