Quality control of fifteen probiotic products containing Saccharomyces boulardii

Aims:  The yeast Saccharomyces boulardii is used as a probiotic for the prevention and treatment of diarrhoea. In this study, the quality of 15 probiotic products containing S. boulardii was verified. Methods and Results:  Using microsatellite typing, the identity of all Saccharomyces strains in the products was confirmed as S. boulardii . Additionally, solid‐phase cytometry (SPC) and a plate method were used to enumerate S. boulardii cells. SPC was not only able to produce results more rapidly than plating (4 h compared to 48 h) but the cell counts obtained with SPC were significantly higher than the plate counts. Finally, we found that <1% of the S. boulardii cells survived 120 min in gastric conditions and storage for 3 months at 40°C with 75% relative humidity. Conclusions:  We developed a SPC method for the quantification of viable S. boulardii cells in probiotics. Additionally, we demonstrated that gastric conditions and storage have a marked effect on the viability of the yeast cells. Significance and Impact of the Study:  To our knowledge, this is the first time SPC is used for the quality control of probiotics with S. boulardii . Additionally, we demonstrated the need for gastric protection and accurate storage.