A comparison of clinical and food Saccharomyces cerevisiae isolates on the basis of potential virulence factors

Abstract

Saccharomyces cerevisiae is the most widely used yeast in industrial/commercial food and beverage production and is even consumed as a nutritional supplement. Various cases of fungemia caused by this yeast species in severely debilitated traumatized or immune-deficient patients have been reported in recent years, suggesting that this species could be an opportunistic pathogen in such patients. To determine whether the industrial S. cerevisiae strains can be included in this virulent group of strains, we carried out a comparative study between clinical and industrial yeasts based on the various phenotypic traits associated with pathogenicity in two other yeast species (Candida albicans and Cryptococcus neoformans). The majority of the clinical isolates were found to secrete higher levels of protease and phospholipase, grow better at 42 degrees C and show strong pseudohyphal growth relative to industrial yeasts. However three industrial yeast strains, one commercial wine strain, baker's yeast and one commercial strain of S. cerevisiae (var. boulardii), were exceptions and based on their physiological traits these yeasts would appear to be related to clinical strains.

Physiological and molecular characterisation of Saccharomyces cerevisiae cachaça strains isolated from different geographic regions in Brazil

“…A similar platting approach has been used by several authors to test wine yeast viability following several stress treatments (Ogawa et al 2000;Carrasco et al 2001;Garay-Arroyo et al 2004;Zuzuarregui and del Olmo 2004;Belloch et al 2008) and measuring growth at different temperature conditions of S. cerevisiae clinical strains (de Llanos et al 2006). Table 2 shows the ability of all S. cerevisiae strains isolated from each cachaça producing state to develop colonies at different dilutions in the most important stress conditions tested, low temperature and high ethanol concentrations.…”

Effect of Oral Administration of the IgE-suppressive Wild Yeast Strain <i>Saccharomyces paradoxus</i> P01 on the Development of Atopic Dermatitis-like Symptoms in NC/Nga Mice

“…These results suggest that the P01 strain is not harmful to NC/Nga mice in this study. However, the possibility remains that live Saccharomyces yeast strains could be opportunistic pathogens in severely debilitated, traumatized or immune-deficient patients (de Llanos et al, 2006). Although the risk of infection can be reduced by using heat-killed yeast, the in vivo safety of oral administration of these wild Saccharomyces strains will need to be carefully evaluated in several models.…”

Determination of MICING: a new assay for assessing minimal inhibitory concentration for invasive growth

“…Phenotypic switching, i.e. pseudohyphae formation, is arguably indirectly involved in pathogenicity [25][26][27] and it is difficult to quantify, while invasive growth, on the other hand, appears to be a more easily measurable and directly related virulence trait. In vivo models for the study of yeast pathogenicity, such as experimental mice [4,18,28], are scarce, and, therefore, in vitro methods need to be better established.…”