ABSTRACT
Saccharomyces cerevisiae is an ubiquitous, ascomycete yeast that has been used in the production of food and beverage since ancient times; therefore, it is frequently referred to as “baker's yeast” or “brewer's yeast.” Although S. cerevisiae has long been considered as a safe microorganism, its role as human pathogen particularly in critically ill and immunocompromised patients only became apparent about two decades ago. 1–3 Since the 1990s, there have been a growing number of reports about its implication as an etiologic agent of invasive infections 4,5 (see also references cited in this chapter). Due to its use in both the traditional and industrial fermentative production of beer, wine, and baked foods, S. cerevisiae has also been promoted by health food enthusiasts as a nutritional supplement in the form of brewer's yeast tablets or powder containing viable organisms. As a consequence, people ingest S. cerevisiae and, therefore, are potentially exposed to the risk of infections due to rarely pathogenic, but problematic, strains from this species. 6,7 In this regard, it is noteworthy that S. cerevisiae is a very heterogeneous species, encompassing clinical isolates and strains used in food production and in the laboratory that tend to have mosaic recombinant genomes. 8
