In Vivo and In Vitro Studies on Virulence and Host Responses to Saccharomyces cerevisiae Clinical and Non-Clinical Isolates

Abstract

We have studied the virulence and host responses to several clinical and non-clinical Saccharomyces cerevisiae isolates: two vaginal isolates (60, 61), one isolate from faeces (20), a brewer's yeast isolate used in dietetics (D14), one S. boulardii isolate from a commercial probiotic product, and a reference natural wine yeast (CECT 10431). Hematogenously disseminated infection in a mouse model demonstrated that four isolates (all, except 20 and 10431) were able to colonize preferentially the brain, as well as kidney and spleen, to a lesser extent, of immunocompetent mice. In vitro adhesion assays to epithelial and endothelial cell lines also showed an increased adherence ability of strains 60, 61, D14 and S. boulardii. In vitro cytokine production assays by RAW 264.7 murine macrophages challenged with yeasts showed a relative increased production of TNF-in response to the 20 and 10431 strains; viability of RAW cells after coculture was similar in all cases (2-5% non-viable cells) except for 60 strain (11% non-viable cells). In vitro phagocytosis assays of yeasts by RAW cells showed that two isolates (D14 and particularly S. boulardii) were engulfed less efficiently. These results point out that S. cerevisiae isolates, from both clinical and non-clinical (dietetic and probiotic) origin, may vary in the expression of putative virulence factors contributing to their ability to develop the infectious process.

Transcriptomics in human blood incubation reveals the importance of oxidative stress response in Saccharomyces cerevisiae clinical strains

“…Several S. cerevisiae isolates were used in this work: a clinical isolate from vagina (isolate 60) [ 7 ], a brewer’s strain isolated from a commercial nutritional complement product (D14) [ 18 ], and two control strains: (one laboratory strain W303 (MATa; ura3-52; trp1Δ2; leu2-3,112; his3-11; ade2-1; can1-100) and a wine strain CECT 10431) [ 18 ]. Isolate 60 and D14 were chosen from a virulent yeast collection obtained from several sources because they have the highest levels in virulence factors and because they were able to survive and colonize the brain of immunocompetent mice after blood infections and cause mice death, showing increased adherence ability [ 3 , 18 ]. Also, they were phagocytosed by macrophages with less efficiency than CECT 10431 [ 18 ].…”

“…Isolate 60 and D14 were chosen from a virulent yeast collection obtained from several sources because they have the highest levels in virulence factors and because they were able to survive and colonize the brain of immunocompetent mice after blood infections and cause mice death, showing increased adherence ability [ 3 , 18 ]. Also, they were phagocytosed by macrophages with less efficiency than CECT 10431 [ 18 ]. The natural wine strain CECT 10431 was used as negative control because it is unable to proliferate in any organ after its intravenous inoculation in murine systems [ 3 , 18 ].…”

“…These studies showed that clinical isolates differed phenotypically from laboratory and wine strains in vitro , but it remains unclear whether these traits also play a role during infection. Comparison of S. cerevisiae clinical and non-clinical strains by molecular typing and determination of putative virulence traits has not revealed a specific virulence factor that clearly separates the strains of clinical origin from the strains of non-clinical origin [ 17 , 18 ]. In addition, little is known about the interactions between S. cerevisiae and host defence cells or non-cellular components [ 18 ].…”

“…We compare two control non-virulent strains with two virulent isolates (60 and D14). These strains showed the highest levels in virulence factors, were able to colonize immunocompetent mice brain after blood infections and cause mice death, showing increased adherence ability whereas other clinical isolates showed low virulence levels [ 3 , 18 ]. Comparison of control and virulent strains revealed that amino acid biosynthesis and elevated oxidative stress response can be of special relevance for survival of S. cerevisiae virulent strains to host defences.…”

Effect of the Oral Administration of Fungal Ligands in a Murine Model of DSS-Induced Colitis

“…Two yeasts strains were used in this study: one strain of S. cerevisiae var boulardii isolated from a commercial probiotic product [26], and the natural wine yeast strain S. cerevisiae CECT (Spanish Type Culture Collection) 10431. These yeast strains were selected as S. boulardii is recognized to have biotherapeutic effects on intestinal mucosa, and the wine yeast strain does not express putative virulence traits [21,26].…”