Invasion of the Probiotics: Iatrogenic Saccharomyces cerevisiae Fungemia

Abstract & Commentary

By Robert Muder, MD, Hospital Epidemiologist, Pittsburgh VA Medical Center, Pittsburgh, Section Editor, Hospital Epidemiology, is associate editor of Infections Disease Alert

Synopsis: Three ICU patients receiving Saccharomyces boulardii (cerevisiae) therapy for treatment of Clostridium difficile colitis experienced fungemia. Review of 60 cases of S. cerevisiae fungemia reported in the literature found that risk factors included presence of a central venous catheter, intravenous or enteral alimentation, and receipt of S. cerevisiae as a probiotic.

Source: Munoz, et al. Saccharomyces cerevisiae Fungemia: An Emerging Infectious Disease. Clin Infect Dis. 2005;40:1625-1634.

Saccharomyces boulardii (recently recognized as a strain of S. cerevisiae rather than a distinct species) is widely used as a probiotic for the treatment of diarrhea and for the prevention and treatment of C. difficile-associated colitis. Munoz and colleagues report 3 patients acquiring S. cerevisiae fungemia during a 2-week period in an intensive care unit. All 3 patients had undergone open heart surgery. All 3 developed C. difficile- associated colitis and received a commercial preparation of S. boulardii along with standard antimicrobial therapy. One of the patients had undergone placement of a mitral valve prosthesis. She had sustained fungemia and evidence of a valvular vegetation on echocardiogram. Molecular typing of the 3 clinical isolates showed them to be identical to the yeast isolated from the probiotic capsules.

Review of the literature identified a total of 60 cases of S. cerevisiae fungemia. Sixty percent of the patients were admitted to the ICU; 93% had a central venous catheter, 71% had received enteral or parenteral nutrition, and 43% had received probiotic Saccharomyces treatment.


S. boulardii (cerevisiae) has been shown in clinical trials to reduce the incidence of C. difficile- associated colitis and to reduce the frequency of relapse. In the laboratory, S. boulardii produces a protease that digests C. difficile toxins A and B;1 this may be the mechanism of the clinical effect. C. boulardii does not, however, appear to affect the course of established C. difficile diarrhea.2 The exact relationship between probiotic use and fungemia is not entirely clear. A likely mechanism is inadvertent contamination of central catheters when the probiotic capsules are opened and administered via nasogastric tube.

This report and literature review demonstrates that, contrary to popular believe, administration of probiotics is not always benign. Patients who are critically ill, who have central catheters, or who are immunosuppressed should not received probiotic therapy. Although there are no clinical trials to guide therapy, S. cerevisiae is typically susceptible to amphotericin. Susceptibility to fluconazole and itraconazole is variable. Limited data suggests that most strains are likely to be susceptible to voriconazole.


  1. Castagliuolo I, et al. Saccharomyces boulardii Protease Inhibits the Effects of Clostridium difficile Toxins A and B in Human Colonic Mucosa. Infect Immunity. 1999;67:302-307.
  2. McFarland LV, et al. A Randomized Placebo-Controlled Trial of Saccharomyces boulardii in Combination with Standard Antibiotics for Clostridium difficile Disease. JAMA. 1994;271:1913-1918.