When I started antibiotic treatment for MAI, my gastroenterologist recommended Florastor. It is Saccharomyces bollardii, and apparently it is the only brand established in (small) studies to survive and work against antibiotic gi effects. That doesn't mean it's the only brand of Saccharomyces bollardii that will be effective, just that it's been studied. I have found it very helpful and have continued it since being off antibiotics even though it's pricey.