Identification of Candida glabrata complex strains isolated from clinical specimens at the species level by molecular methods and determination of their susceptibilities to antifungals

YASEMİN AYŞE UÇAR

Identification of Candida glabrata complex strains isolated from clinical specimens at the species level by molecular methods and determination of their susceptibilities to antifungals

Thesis Type: Postgraduate

Institution Of The Thesis: Istanbul University, Health Sciences Institute, İstanbul Tıp Fakültesi Bölümü, Turkey

Approval Date: 2023

Thesis Language: Turkish

Student: YASEMİN AYŞE UÇAR

Supervisor: Gonca Erköse Genç

Open Archive Collection: AVESIS Open Access Collection

Abstract:

Candida glabrata is a member of microbiota of gastrointestinal tract and mucocutaneous membranes in humans. In the presence of risk factors, it causes opportunistic infections. Resistance or decreased susceptibility to fluconazole can be observed in strains, and an increase in the frequency of resistance to echinocandins has been reported in recent years. Two new species, Candida nivariensis and Candida bracarensis, are classified together with C. glabrata sensu stricto in C. glabrata complex. These two new species were isolated as the causative agent of various superficial and invasive infections, and they were determined to be more resistant and virulent than C. glabrata. However, they cannot be distinguished from C. glabrata by phenotypic and biochemical methods and can be misidentified. In this study, a total of 40 strains isolated from various clinical specimens and identified as C. glabrata by biochemical-based systems were identified at the species level by sequencing of ITS regions and their susceptibility to antifungals was investigated with Sensititre YeastOne susceptibility panel. All strains (100%) were determined to be C. glabrata sensu stricto, while C. nivariensis and C. bracarensis were not found. The minimum inhibitory concentration (MIC) values obtained were evaluated according to the species specific clinical breakpoints and epidemiological cut-off values determined by Clinical and Laboratory Standards Institute (CLSI). It was determined that all strains (100%) were susceptible dose-dependent to fluconazole; 39 strains (97.5%) were susceptible, one (2.5%) was resistant to caspofungin, anidulafungin and micafungin. All strains (100%) for amphotericin B and itraconazole, 37 (92.5%) strains for posaconazole, and 36 (90%) strains for voriconazole were found to be wild type (WT). It was thought that more research should be done on epidemiology, virulence factors and resistance profiles of C. nivariensis and C. bracarensis, and it is important in the routine microbiology laboratories to correctly identify C. glabrata complex isolates at the species level and to determine susceptibility to antifungals.