Frequency of Uncommon Clinical Yeast Species Confirmed by ITS-Sequencing

Accurate speciation of the clinical yeast isolates is essential to a targeted treatment. The aim of this study was to identify and determine the frequency of uncommon and rare yeast species causing fungal infections that may be misidentified. During a 10-month period, yeast isolates collected from patients referring to or hospitalized in some educational hospitals in Tehran, Iran, were included in this study. In addition to conventional methods such as direct microscopy and culture on CHROMagar Candida, molecular methods including PCR-RFLP and ITS-sequencing were used for the accurate identification of the yeast strains. Among 930 yeast isolates recovered from normally sterile and other clinical specimens, a total number of 27 strains were identified as uncommon Candida species and three were identified as rare non-Candida species yeasts. They included C. kefyr (n = 12), C. lusitaniae (n = 8), C. intermedia (n = 3), C. orthopsilosis, C. guilliermondii, and Trichosporon asahii (each n = 2), and Magnusiomyces capitatus (n = 1). The isolation of less common or rare yeast species, which can cause a variety of infections from superficial to systemic infections, is increasingly reported. Since this uncommon yeast species may exhibit low susceptibility to some antifungal agents, the use of reliable methods for accurate screening of these yeasts is necessary.