S. Boulardii is a yeast, not a bacteria, in case you didn't know. I tried one capsule of it, and the next day I felt awful - nausea, dizziness, felt like my brain was being poisoned. I suspect it killed some Candida and released mercury or other heavy metals. At least that's what it felt like. Also had some intestinal discomfort for about 6 days as the yeast made its way through the intestines. There is one member on here who has a systemic yeast infection from S. boulardii. You can search here read what she said about it. Not to scare you just to make you aware.