Saccharomyces boulardii and Candida albicans experimental colonization of the murine gut.

Saccharomyces boulardii has been and continues to be extensively used as a probiotic, with only rare associations with fungemia. This study evaluated the virulence of this yeast when given as a probiotic, and its role in preventing gastrointestinal (GI) colonization by Candida. Adult male Crl:CD1 (ICR) BR mice were given S. boulardii orally in three different doses or normal saline for 14 days. Stool cultures were performed at the time of discontinuation of yeast administration, as well as 1 and 2 weeks later. Gut colonization was proportional to the given dose but lasted only 1 week and no dissemination of the yeast was detected. S. boulardii was also given for 2 and 4 weeks to mice fed chow containing Candida albicans. S. boulardii in the gut did not affect Candida GI colonization. These findings suggest that oral administration of S. boulardii induces a substantial but short term increase of this yeast in the intestinal lumen and administration of the probiotic does not prevent subsequent GI colonization by C. albicans.

Effects of levofloxacin, moxifloxacin and prulifloxacin on murine gut colonization by Candida albicans.

Fluoroquinolones are broad-spectrum antibiotics increasingly utilized as empirical or prophylactic therapy in the management of cancer patients. We evaluated the effects of newer generation fluoroquinolones on the level of gastrointestinal (GI) colonization by Candida albicans in a previously established mouse model. Adult male Crl:CD1 (ICR) BR mice were fed chow containing Candida albicans or regular chow. The mice fed the Candida chow had their gut colonized by the yeast. Both groups were subsequently given levofloxacin, moxifloxacin, prulifloxacin or normal saline for 10 days. Stool cultures were performed immediately before, at the end, and one week after discontinuation of treatment to determine the level of intestinal yeast colonization. Candida-colonized mice treated with fluoroquinolones had substantially higher yeast counts in their stools than control mice fed Candida containing chow but treated with saline. Mice fed regular chow and treated with the study antibiotics or saline did not have any Candida in their stools. Dissemination of Candida to internal organs was not observed in any animal. In conclusion, we have shown that all fluoroquinolones tested induced substantial increases in the murine intestinal concentration of C. albicans.