Abstract
Identification of the emerging yeast species Candida nivariensis among presumptively identified Iranian Candida glabrata isolates. Clinical C. glabrata species complex isolates from blood (n=71; 33.3 %), urine (n=100; 46.9 %), vaginal swabs (n=20;9.4 %), BAL (n=10; 4.7 %), and sputum (n=12; 5.6 %) from Iran were investigated. Isolates were characterized by CHROMagar, multiplex PCRs, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), amplified fragment length polymorphism (AFLP) fingerprinting, internal transcribed spacer (ITS)/large subunit (LSU) rDNA and FKS1/FKS2 sequencing, and the European Committee on Antimicrobial Susceptibility Testing broth microdilution method. A comprehensive literature review was conducted and all the relevant clinical and microbiological data were collected. Four C. nivariensis isolates were recovered from blood samples of three subjects and were all consistently identified by nine-plex PCR, Bruker MALDI-TOF MS, and LSU and ITS rDNA sequencing. AFLP genotyping clustered the isolates into two groups. Sequencing of the FKS1 and FKS2 hotspots showed no accountable amino acid substitutions. All isolates were susceptible to amphotericin B, fluconazole, itraconazole, posaconazole, voriconazole, anidulafungin and micafungin. In total, 4 out of 213 clinical C. glabrata species complex candidemia isolates were C. nivariensis. Improvement of the BioMerieux Vitek MS database is required to accurately identify C. nivariensis and it is advised to alternatively use CHROMagar and/or PCR-based techniques. As other species within the Nakaseomyces clade may cause infection and showed high MIC values for antifungals, inclusion of their spectra into the MALDI-TOF MS database seems relevant. Due to developing resistance to fluconazole and insufficient efficacy of caspofungin, the combination of catheter removal plus treatment with caspofungin, or voriconazole, or micafungin might be effective for patients.
Highlights
Candida glabrata is the second most common cause of candidemia in the USA [1] and its prevalence is increasing worldwide [2, 3]
Four C. nivariensis isolates were recovered from blood samples of three subjects and were all consistently identified by nine-plex PCR, Bruker MALDI-TOF MS, and large subunit (LSU) and internal transcribed spacer (ITS) ribosomal DNA (rDNA) sequencing
All isolates were susceptible to amphotericin B, fluconazole, itraconazole, posaconazole, voriconazole, anidulafungin and micafungin
Summary
Candida glabrata is the second most common cause of candidemia in the USA [1] and its prevalence is increasing worldwide [2, 3]. For a decade C. glabrata has been recognized as a cryptic species complex containing the emerging opportunistic yeast species C. nivariensis [6] and Candida bracarensis [7]. These species belong to the Nakeseomyces clade of the Saccharomycotina [8]. Some studies showed that time-consuming, but relative simple phenotypic identification techniques, such as CHROMagar, can distinguish these species from C. glabrata, molecular assays increased the accuracy and shortened the identification turn-around time [9]. Identification and sharing data on nationwide and worldwide scales could enrich our knowledge about various aspects of these species and will contribute to diagnostic and even therapeutic improvement
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