Yeasts are single celled organisms that are ubiquitous in our environment. They are commonly found on many plants, including fruits and vegetables. They exist as normal flora both inside and outside of our bodies on mucocutaneous membranes of humans, particularly the gastrointestinal and female genital tracts. Yeasts are often detected in many clinical specimens, but normally have no clinical significance. The most commonly isolated species is Candida albicans.
Candida species are the primary cause of opportunistic yeast infections.
It is the fourth most common organism isolated from the blood of hospitalized patients in the United States. Although it is found as normal flora, in the imunocompromised patient, it can invade the blood and body tissues producing an invasive life threatening disease. The defense mechanism against systemic candidiasis is carried by polymorphonuclear leukocytes which have the capacity to phagocytize and kill Candida. Neutrophils and monocytes lacking myeloperoxidase or the capacity to generate hydrogen peroxidase and superoxide anion, fail to kill C. albicans effectively. Consequently, patients who are on long term antibiotic therapy with a compromised neutrophil count are more susceptible to C. albicans infection.