Is Brewers Yeast the same as Saccharomyces Boulardii?
Brewer’s Yeast (Saccharomyces Cerevisiae) and Florastor (Saccharomyces Boulardii) are not the same organism. They are both yeasts and have similarities, but they are distinctly different strains within the same species. There are many studies that show S. Boulardii is beneficial in the treatment of C Diff. However, there is only anecdotal evidence (not fully reliable) that Brewer’s Yeast is beneficial in treating C Diff.
Until something has been proven to be beneficial in treating C Diff, you have to weigh the possible side effects. For example, there are cases of fungemia (dangerous fungus infection in the blood) being associated with the use of Brewer’s Yeast (Saccharomyces Cerevisiae). 
So, until (or if) we see more evidence, my thought while trying to get rid of C Diff was to use Florastor (Saccharomyces Boulardii) instead.
 Saccharomyces cerevisiae fungemia: an emerging infectious disease.
Munoz P; Bouza E; Cuenca-Estrella M; Eiros JM; Perez MJ; Sanchez-Somolinos M; Rincon C; Hortal J; Pelaez T
Clin Infect Dis 2005 Jun 1;40(11):1625-34. Epub 2005 Apr 25.