Saccromyces boulardii may indeed combat c. difficile. However, I tried it to no avail for my dog. She suffered from recurring bouts of c. difficile (confirmed multiple times by the vet) and I did try saccromyces boulardii for 9 months. It didn't help. I don't know if it was because it was truly ineffective or inactive because of heat incurred from shipping and in proper storage at the store. I refrigerated it as soon as I got it home, but it made no difference in her bouts of diarrhea. I finally cured it for good with oregano oil for 6 months. I gave her 4 drops in a capsule twice a day for 6 months. It's been 2 years now and she's had no more bouts of diarrhea.