What is Saccharomyces (a type of fungus)?

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Last updated: February 26, 2025 • View editorial policy

From the Guidelines

Saccharomyces is a genus of yeast that includes several important species, most notably Saccharomyces cerevisiae, commonly known as baker's yeast or brewer's yeast, and Saccharomyces boulardii, a probiotic used to treat and prevent various gastrointestinal disorders. The use of Saccharomyces boulardii as a probiotic has been studied in several clinical trials, with evidence suggesting its effectiveness in preventing antibiotic-associated diarrhea and recurrent Clostridium difficile infections 1, 2.

  • The typical dosage of S. boulardii is 250-500 mg taken 1-2 times daily for adults, with treatment continuing throughout antibiotic therapy and for several days afterward.
  • Saccharomyces works by competing with harmful bacteria for resources in the gut, strengthening the intestinal barrier, and modulating immune responses. Some studies have reported that S. boulardii may increase the cessation of diarrhea and decrease the recurrence of diarrhea in patients with Clostridium difficile infection 2, 3.
  • However, the quality of evidence is generally considered low due to the heterogeneity of the studies and the risk of bias in some trials. The American Gastroenterological Association (AGA) suggests the use of S. boulardii or other specific probiotic strains for the prevention of Clostridium difficile infection in adults and children receiving antibiotic treatment 1, 4.
  • The AGA also recommends against the use of probiotics in patients with severe illnesses or those who are immunocompromised. Overall, while the evidence is not yet conclusive, Saccharomyces boulardii appears to be a promising probiotic for the prevention and treatment of certain gastrointestinal disorders, particularly antibiotic-associated diarrhea and recurrent Clostridium difficile infections.

From the Research

Definition and Properties of Saccharomyces

  • Saccharomyces is a genus of fungus, with Saccharomyces boulardii being a specific type that has been classified as a probiotic agent 5.
  • It has unique properties such as viability over a wide pH range, inability to acquire antibiotic resistance genes, and the ability to achieve a steady state rapidly 5.
  • Saccharomyces boulardii is a nonpathogenic yeast that has been widely used to prevent antibiotic-associated diarrhea (AAD) 6.

Uses and Effects of Saccharomyces boulardii

  • Prophylactic use of Saccharomyces boulardii has been shown to reduce the incidence of antibiotic-associated diarrhea in hospitalized patients 7, 6.
  • It has also been found to be effective in preventing pediatric acute gastroenteritis (PAGE) and restoring the diversity of gut microbiota 5.
  • Saccharomyces boulardii has been recommended in several international guidelines for the management of acute diarrhea 5.

Safety and Potential Risks

  • While Saccharomyces boulardii is considered a safe probiotic for use in children and adults, there have been reports of fungemia following probiotic treatment with Saccharomyces cerevisiae var. boulardii 8, 9.
  • These cases highlight the need for careful evaluation of the potential benefits and risks of using Saccharomyces boulardii, especially in elderly or immunocompromised patients 9.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.