Comparison of the accuracy of two conventional phenotypic methods and two MALDI-TOF MS systems with that of DNA sequencing analysis for correctly identifying clinically encountered yeasts.

Ilse D Jacobsen,Qiao-Ting Chao,Tai-Fen Lee,Po-Ren Hsueh,Li-Yun Peng,Shih-Hua Teng,Ping-Hung Chen,Lee-Jene Teng

doi:10.1371/journal.pone.0109376

Ilse D Jacobsen, Qiao-Ting Chao + Show 6 more

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https://doi.org/10.1371/journal.pone.0109376

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Abstract

We assessed the accuracy of species-level identification of two commercially available matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) systems (Bruker Biotyper and Vitek MS) and two conventional phenotypic methods (Phoenix 100 YBC and Vitek 2 Yeast ID) with that of rDNA gene sequencing analysis among 200 clinical isolates of commonly encountered yeasts. The correct identification rates of the 200 yeast isolates to species or complex (Candida parapsilosis complex, C. guilliermondii complex and C. rugosa complex) levels by the Bruker Biotyper, Vitek MS (using in vitro devices [IVD] database), Phoenix 100 YBC and Vitek 2 Yeast ID (Sabouraud's dextrose agar) systems were 92.5%, 79.5%, 89%, and 74%, respectively. An additional 72 isolates of C. parapsilosis complex and 18 from the above 200 isolates (30 in each of C. parapsilosis, C. metapsilosis, and C. orthopsilosis) were also evaluated separately. Bruker Biotyper system could accurately identify all C. parapsilosis complex to species level. Using Vitek 2 MS (IVD) system, all C. parapsilosis but none of C. metapsilosis, or C. orthopsilosis could be accurately identified. Among the 89 yeasts misidentified by the Vitek 2 MS (IVD) system, 39 (43.8%), including 27 C. orthopsilosis isolates, could be correctly identified Using the Vitek MS Plus SARAMIS database for research use only. This resulted in an increase in the rate of correct identification of all yeast isolates (87.5%) by Vitek 2 MS. The two species in C. guilliermondii complex (C. guilliermondii and C. fermentati) isolates were correctly identified by cluster analysis of spectra generated by the Bruker Biotyper system. Based on the results obtained in the current study, MALDI-TOF MS systems present a promising alternative for the routine identification of yeast species, including clinically commonly and rarely encountered yeast species and several species belonging to C. parapsilosis complex, C. guilliermondii complex, and C. rugosa complex.

Highlights

Invasive candidiasis and candidemia remain leading causes of morbidity and mortality in immunocompromised hosts, among patients with hematological malignancies in intensive care units [1,2,3,4,5]
Among the 90 isolates of C. parapsilosis complex, all were subjected to cluster analysis by the Bruker Biotyper system and 18 randomly selected isolates were used for assessment of the accuracy of two commercially available MALDI-TOF MS systems and two conventional phenotypic methods
Using the Vitek 2 Yeast ID system, one C. albicans isolate was identified as C. albicans/C. famata on BAP

Summary

Introduction

Invasive candidiasis and candidemia remain leading causes of morbidity and mortality in immunocompromised hosts, among patients with hematological malignancies in intensive care units [1,2,3,4,5]. Optimal and early therapy has been shown to significantly reduce the incidence of morbidity and mortality in patients with invasive yeast infections and has been shown to be associated with an overall reduction in cost of hospital care for these patients [5]. Candida albicans remains the predominant agent responsible for healthcare-associated infections, non-albicans Candida species, such as C. glabrata, C. parapsilosis complex, C. tropicalis, C. guilliermondii complex, C. dubliniensis, C. lusitaniae, and C. krusei have emerged as significant opportunistic pathogens [2,3,4].

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