SPECIES IDENTIFICATION AND VIRULENCE ATTRIBUTES OF SACCHAROMYCES-BOULARDII (NOM. INVAL.)

Saccharomyces boulardii (nom. inval.) has been used for the treatment of several types of diarrhea, Recent studies have confirmed that S. bo ulardii is effective in the treatment of diarrhea, in particular chron ic or recurrent diarrhea, and furthermore that it is a safe and well-t olerated treatment. The aim of the present study was to identify strai ns of S. boulardii to the species level and assess their virulence in established murine models. Three strains of S. boulardii were obtained from commercially available products in France and Italy. The three S . boulardii strains did not form spores upon repeated testing. Therefo re, classical methods used for the identification of Saccharomyces spp , could not be undertaken. Typing by using the restriction fragment Le ngth polymorphisms (RFLPs) of the PCR-amplified intergenic transcribed spacer regions (including the 5.8S ribosomal DNA) showed that the thr ee isolates of S. boulardii were not separable from authentic isolates of Saccharomyces cerevisiae with amy of the 10 restriction endonuclea ses assessed, whereas 9 of the 10 recognized species of Saccharomyces could be differentiated. RFLP analysis of cellular DNA with EcoRI show ed that all three strains of S, boulardii had identical patterns and w ere similar to other authentic S. cerevisiae isolates tested. Therefor e, the commercial strains of S. boulardii available to us cannot be ge notypically distinguished from S. cerevisiae, Two S. boulardii strains were tested in CD-1 and DBA/2N mouse models of systemic disease and s howed intermediate virulence compared with virulent and avirulent stra ins of S. cerevisiae. The results of the present study show that these S. boulardii strains are asporogenous strains of the species S. cerev isiae, not representatives of a distinct and separate species, and pos sess moderate virulence in murine models of systemic infection. Theref ore, caution should be advised in the clinical use of these strains in immunocompromised patients until further study is undertaken.