FROM WIKIPEDIA about Saccharomyces cerevisiae: "A human pathogen Saccharomyces cerevisiae is proven to be an opportunistic human pathogen, though of relatively low virulence.[67] Despite widespread use of this microorganism at home and in industry, contact with it very rarely leads to infection.[68] Saccharomyces cerevisiae was found in the skin, oral cavity, oropharinx, duodenal mucosa, digestive tract, and vagina of healthy humans[69] (one review found it to be reported for 6% of samples from human intestine[70]). Some specialists consider S. cerevisiae to be a part of the normal microbiota of the gastrointestinal tract, the respiratory tract, and the vagina of humans,[71] while others believe that the species cannot be called a true commensal because it originates in food.[70][72] Presence of S. cerevisiae in the human digestive system may be rather transient;[72] for example, experiments show that in the case of oral administration to healthy individuals it is eliminated from the intestine within 5 days after the end of administration.[70][68] Under certain circumstances, such as degraded immunity, Saccharomyces cerevisiae can cause infection in humans.[68][67] Studies show that it causes 0.45-1.06% of the cases of yeast-induced vaginitis. In some cases, women suffering from S. cerevisiae-induced vaginal infection were intimate partners of bakers, and the strain was found to be the same that their partners used for baking. As of 1999, no cases of S. cerevisiae-induced vaginitis in women, who worked in bakeries themselves, were reported in scientific literature. Some cases were linked by researchers to the use of the yeast in home baking.[67] Cases of infection of oral cavity and pharynx caused by S. cerevisiae are also known.[67] Invasive and systemic infections Occasionally Saccharomyces cerevisiae causes invasive infections (i. e. gets into the bloodstream or other normally sterile body fluid or into a deep site tissue, such as lungs, liver or spleen) that can go systemic (involve multiple organs). Such conditions are life-threatening.[67][72] More than 30% cases of S. cerevisiae invasive infections lead to death even if treated.[72] S. cerevisiae invasive infections, however, are much rarer than invasive infections caused by Candida albicans[67][73] even in patients weakened by cancer.[73] S. cerevisiae causes 1% to 3.6% nosocomial cases of fungemia.[72] A comprehensive review of S. cerevisiae invasive infection cases found all patients to have at least one predisposing condition.[72] Saccharomyces cerevisiae may enter the bloodstream or get to other deep sites of the body by translocation from oral or enteral mucosa or through contamination of intravascular catheters (e. g. central venous catheters).[71] Intravascular catheters, antibiotic therapy and compromised immunity are major predisposing factors for S. cerevisiae invasive infection.[72] A number of cases of fungemia were caused by intentional ingestion of living S. cerevisiae cultures for dietary or therapeutic reasons, including use of Saccharomyces boulardii (a strain of S. cerevisiae which is used as a probiotic for treatment of certain forms of diarrhea).[67][72] Saccharomices boulardii causes about 40% cases of invasive Saccharomyces infections[72] and is more likely (in comparison to other S. cerevisiae strains) to cause invasive infection in humans without general problems with immunity,[72] though such adverse effect is very rare relative to Saccharomices boulardii therapeutic administration.[74] S. boulardii may contaminate intravascular catheters through hands of medical personnel involved in administering probiotic preparations of S. boulardii to patients.[72] Systemic infection usually occurs in patients who have their immunity compromised due to severe illness (HIV/AIDS, Leukemia, other forms of cancer) or certain medical procedures (bone marrow transplantation, abdominal surgery).[67] A case was reported when a nodule was surgically excised from a lung of a man employed in baking business, and examination of the tissue revealed presence of Saccharomyces cerevisiae. Inhalation of dry baking yeast powder is supposed to be the source of infection in this case.[75][72]