CNCM I-745 (patented strain)
The exact strain of Saccharomyces boulardii with the most clinical trials in the world
Definition
CNCM I-745 is the official designation of the patented strain of the probiotic yeast Saccharomyces boulardii, deposited in the National Collection of Microorganism Cultures at the Institut Pasteur in Paris. It is the only S. boulardii strain with an extensive clinical dossier — over 100 trials — and the one to which the actual evidence on antibiotic-associated diarrhea, traveler's diarrhea and Clostridioides difficile infection applies. In probiotics, strain specificity is decisive: the effects demonstrated for CNCM I-745 cannot be extrapolated to other products labeled generically as "boulardii."
Detailed explanation
The yeast was isolated in 1920 by French microbiologist Henri Boulard from the skin of lychee and mangosteen, after he observed locals in Southeast Asia using it against dysentery. Genomically, CNCM I-745 shares more than 99% nucleotide identity with Saccharomyces cerevisiae (baker's yeast), yet it is distinguished by stable traits: absence of the hexose transporters HXT9 and HXT11, an inability to use galactose, and an optimal growth temperature of 37 °C, close to body temperature.
Unlike bacterial probiotics, it is a yeast and therefore intrinsically resistant to antibiotics, which allows it to transiently colonize the gut during an antibiotic course. Its mechanisms are multiple: it secretes a 54 kDa protease that degrades C. difficile toxins A and B and their receptors; it produces a phosphatase that inactivates lipopolysaccharide endotoxin; it reinforces the intestinal barrier and modulates the mucosal immune response.
Meta-analyses of randomized trials credit S. boulardii with roughly a 50% reduction in the risk of antibiotic-associated diarrhea. It should not be used in immunocompromised patients or those with a central venous catheter, owing to the rare risk of fungemia.
Scientific sources
- PubMed — Saccharomyces boulardii CNCM I-745: A Non-bacterial Microorganism Used as Probiotic Agent (Pais et al., Current Microbiology 2020)
- PubMed — Saccharomyces boulardii in the treatment and prevention of antibiotic-associated diarrhea (McFarland)
- Source — The Saccharomyces boulardii CNCM I-745 Strain Shows Protective Effects against the B. anthracis LT Toxin (Toxins 2015)
- Source — Effectiveness of Saccharomyces boulardii CNCM I-745 in acute inflammatory viral diarrhoea: a randomized trial (BMC Gastroenterology 2023)
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