Fungemia, Other Fungal Infections Associated With S. boulardii Probiotics

Judy Stone, MD

July 16, 2021

Life-threatening fungal bloodstream infections associated with probiotic supplements have been reported in the journal Emerging Infectious Diseases by a group of researchers in Finland. While individuals consume these mixtures of bacteria and yeast in the hopes of "balancing" their microbiome or preventing diarrhea from antibiotic use, some died or developed yeast infections requiring prolonged antifungal treatment.

In a retrospective registry study at five university hospitals in Finland, the researchers found 46 patients between 2009 and 2018 with Saccharomyces sp. of yeast in their blood associated with ingesting probiotics. At least 20 (43%) had been using S. cerevisiae var. boulardii as a probiotic, with the organism then causing a bloodstream infection. Overall, 37% of the fungemic patients died.

Juha Rannikko, MD, lead author and infectious disease faculty member at Tampere University Hospital, Finland, told Medscape Medical News that there were an additional 1153 nonblood isolates of Saccharomyces. He expressed surprise at the large number of nonblood isolates, saying: "If is about 10 nonblood Saccharomyces boulardii-associated findings for each Saccharomyces boulardii-associated fungemia."

Most of the yeast infections (59%) occurred in patients with underlying gastrointestinal disease. Prior studies suggested that patients receiving enteral nutrition might become ill from translocation of the yeast from the inflamed GI tract.

If there were positive cultures for yeast from sites other than blood, physicians changed the antibiotics in 38% of patients.

Conventional wisdom has been that patients receiving broad-spectrum antibiotics should also receive an S. cerevisiae var. boulardii probiotic to prevent Clostridioides difficile infections. Rannikko and coauthors questioned this, noting results of such studies of prophylaxis were equivocal. "There is not enough evidence that clinicians should use Saccharomyces (probiotics) alongside antibiotics," Rannikko concluded.

Laila Woc-Colburn, MD, associate professor at the Emory University School of Medicine, Atlanta, Georgia, told Medscape Medical News that although the study was well done and was published in the journal Emerging Infectious Diseases, the findings do not represent an "emerging" infectious disease. "We have known this for a while — since the 1990s," she said. Warnings about probiotics are part of the standard advice Woc-Colburn gives transplant, chemotherapy, or immunosuppressed patients. "Don't do these probiotics because this is what's going to happen," she tells them. And she told Medscape Medical News, "If I see this in the blood, the first question I'm going to ask my patients is...what probiotic were you drinking?"

Woc-Colburn said the Finnish researchers "did their due diligence" when conducting the study. "They were clear on their limitations. And they came out to the same conclusion as the 2005 Muñoz paper: that if we have some GI disruption, we should not be taking probiotics."

She acknowledged that the Emerging Infectious Diseases study adds a substantial number of cases to those previously reported in the literature and confirms previous findings and recommendations to avoid probiotics if immunosuppressed or acutely ill.

Rannikko and Woc-Coburn have reported no relevant financial relationships. Rannikko has received a lecture fee from Novo Nordisk and a virtual congress attendance fee from Roche.

Emerg Infect Dis. 2021;27:2043-2051. Full text

Judy Stone, MD, is an infectious disease specialist and author of Resilience: One Family's Story of Hope and Triumph Over Evil and Conducting Clinical Research, the essential guide to the topic. You can find her at or on Twitter @drjudystone.

Follow Medscape on Facebook, Twitter, Instagram, and YouTube.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.