Phenotypic and genotypic analysis of clonal clinical isolates of Nakaseomyces glabratus ( Candida glabrata )

Nakaseomyces glabratus (formerly Candida glabrata) is an emerging and opportunistic fungal pathogen that possesses a set of virulence attributes allowing it to survive and colonize new niches within its host. The objective of this study is to determine patterns of phenotypic and genotypic variation in clonal clinical isolates from different patients that occur during an infection. We analyzed 35 clonal clinical isolates of N. glabratus from 10 patients, which we first identified with species-specific primers and genotyped with six polymorphic molecular markers. We characterized the susceptibility to three classes of antifungals, the ability to adhere and form biofilms on polystyrene, the response to thermal stress and oxidative stress caused by different oxidizing agents, and we analyzed the enzymatic activity of the catalase. We found that the N. glabratus clinical isolates analyzed from each patient share a clonal origin but differ from isolates from other patients. We found that the isolates can grow in a wide range of temperatures and acute and chronic stress conditions such as oxidative stress. Isolates from patient 9 (P9) displayed higher resistance to acute exposure to H2O2 in stationary phase (SP) cells than the standard laboratory strain BG14, and this correlates with a higher activity of the only catalase enzyme (Cta1) of N. glabratus. In addition, we identified a case of phenotypic variation among clonal isolates derived from the same patient.