- Presence of Salmonella, Shigella, Campylobacter, Yersinia, Giardia lamblia, Entamoeba histolytica, Microsporidia, Isospora, Cyclospora, or Clostridium difficile toxin in stool (based on assessment within 14 days prior to enrollment by stool ova and parasite examination, culture, and C. difficile assay).