All patients will receive a journal to track their kefir intake (if in Group C) and any loose stools or diarrhea for 30 days after their hospital stay. Additionally, all patients will receive a follow-up phone call 3-5 days after discharge from the hospital, and weekly thereafter for 30 days, to determine if diarrhea has occurred. All patients will be instructed to call their physician if symptoms of diarrhea occur. The aims of this study are to determine the incidence of antibiotic-associated diarrhea in each of the study groups as well as the presence of C. difficile in the stool of those patients that report having diarrhea.