Identification, molecular characterization, and antifungal susceptibility of Cyberlindnera fabianii strains isolated from urinary tract

Objectives

Cyberlindnera fabianii is an opportunistic pathogen isolated from clinical specimens. It can be incorrectly identified as Candida utulis by phenotypic methods. This study aimed to accurately identify Cy.fabianii strains isolated from the urinary tract, and to determine their molecular characterization and antifungal susceptibilities as well.

Methods

Twenty-nine yeast strains isolated from urinary tract samples were studied. Strains were identified by phenotypically, sequence analysis and MALDI-TOF MS. Sequence analysis using different gene regions (ITS1-2,D1/D2,EF-1-alpha) in ribosomal DNA was performed for the molecular analysis. Phylogenetic analysis was done by the neighbor-joining method. Antifungal susceptibilities of strains were determined for nine antifungals by reference broth microdilution and the Sensititre YeastOne broth microdilution method (Sensititre^TMYeastOne^TMAST Plate, Thermo Fisher Scientific™,USA) according to CLSI M60-Ed2 recommendations.

Results

All strains were identified as C.utulis phenotypically by conventional methods, however all strains were identified as Cy.fabianii by sequence analysis and MALDI-TOF MS. It was observed that the gene regions examined in terms of determining evolutionary relatedness did not show intraspecies nucleotide variations. In all strains, the MIC50/MIC90 values for fluconazole were higher than the other antifungals tested.

Conclusion

Cy.fabianii should be considered in fluconazole-resistant urinary tract yeast infections. Although conventional phenotypical methods were insufficient to identify Cy.fabianii, it could be correctly identified with sequence analysis using different gene regions (ITS1-2,D1/D2,EF-1-alpha) in ribosomal DNA and MALDI-TOF MS.