Oligonucleotide Array and VITEK Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry in Species Identification of Blood Yeast Isolates.

Ming-Chi Li,Tsung C Chang,Susan S.-J Lee,Ching-Chi Lee,Ling-Shan Syue,Hung-Mo Chen,Wen-Chien Ko,Shu-Li Su,Chi-Jung Wu,Po-Lin Chen,Chia-Wen Li,Nan-Yao Lee

doi:10.3389/fmicb.2018.00051

Abstract

We evaluated matrix-assisted laser desorption ionization time-of-flight mass spectrometry using VITEK MS (IVD database) and an oligonucleotide array based on the internal transcribed spacer-1 (ITS-1) and ITS-2 sequences of rRNA genes for the identification of Candida spp. from blood cultures. Five-hundred and twelve consecutive bloodstream yeast isolates were collected daily and initially identified by the phenotypic automated method (VITEK YBC or VITEK2 YST card). Inconsistent results were confirmed by D1-D2 region of 28S rRNA genes and ITSs. Excluding two unidentified yeast isolates, the oligonucleotide array and VITEK MS correctly identified 99.6% (508) and 96.9% (494) of 510 yeast isolates, respectively. The oligonucleotide array and VITEK MS demonstrated high correct identification rates for four major Candida species (C. albicans 100%, 98.4%; C. glabrata 100%, 100%; C. parapsilosis 100%, 93.3%; C. tropicalis 100%, 97.3%), but lower correct identification rates for other Candida species (91.7 and 87.5%, respectively). In conclusion, the identification performance of the oligonucleotide array is comparable to that of VITEK MS, and can serve as a supplemental tool for the identification of Candida species.

Highlights

Candidemia remains one of the most important invasive fungal infections, is associated with a high mortality rate, and is a significant healthcare burden (Hassan et al, 2009)
All blood samples were incubated in BACTEC FX (Becton, Dickinson and Company, Sparks, MD, United States), and the laboratory yeast isolates were identified by the VITEK Yeast Biochemical Card (YBC) before 2012 and VITEK 2 YST ID Card after 2012
Of the 512 yeast isolates, C. albicans, C. tropicalis, C. glabrata, and C. parapsilosis accounted for 49.4% (n = 253), 21.5% (n = 110), 11.7% (n = 60), and 11.7% (n = 60), respectively

Summary

Introduction

Candidemia remains one of the most important invasive fungal infections, is associated with a high mortality rate (up to 30%), and is a significant healthcare burden (Hassan et al, 2009). An oligonucleotide array based on the internal transcribed spacer-1 (ITS-1) and ITS-2 sequences of rRNA genes was developed for diagnosis of invasive fungal infections and species identification (Hsiao et al, 2005; Leaw et al, 2007; Hsiue et al, 2010; Kuo et al, 2012; Li et al, 2016). Similar to MALDI-TOF MS, the array showed superiority to conventional identification methods for Candida species found in blood cultures (Hsiue et al, 2010). Both MALDITOF MS and the oligonucleotide array can be used in clinical care

Methods

Results

Conclusion