Comparative Evaluation of the Bruker Biotyper and Vitek MS Matrix-Assisted Laser Desorption Ionization–Time Of Flight (MALDI-TOF) Mass Spectrometry Systems for Identification of Yeasts of Medical Importance

Abstract

We report the first comparative evaluation between the Bruker Biotyper MS (BMS) and the Vitek MS (VMS) for the identification of yeasts. The rate of correct identifications at the species level was comparable using the commercial databases (89.8% versus 84.3%; P ‫؍‬ 0.712), but higher for BMS using an in-house-extended database (100% versus 84.3%; P ‫؍‬ 0.245). Importantly, the rate of misidentification was significantly higher for VMS (1% versus 12.1%; P < 0.0001), including the rate of major errors (0% versus 4.5%; P ‫؍‬ 0.0036). The introduction of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) in the clinical microbiology laboratories is changing the approach to bacterial and fungal identification (1-4). In particular, several studies have already demonstrated the reliability of MALDI-TOF MS in the rapid identification of yeasts in different clinical settings (5-7), evidencing its cost-effectiveness in allowing the initiation of species-targeted antifungal therapy (7-9). To date, four MALDI-TOF MS systems are commercially available: the Microflex LT Biotyper (Bruker Daltonics, Bremen, Germany) (BMS), the Saramis system (bio-Mérieux, Marcy l'Etoile, France), the Vitek MS system (bioMérieux, Marcy l'Etoile, France) (VMS), and, very recently, the Andromas system (Andromas, Paris, France). Several comparative studies have already been performed using the most common systems (BMS and VMS), but, to the best of our knowledge, they have focused only on the identification of bacteria (10-13). Only very recently was a comparative study on yeasts performed using BMS and Saramis (bio-Mérieux, Marcy l'Etoile, France), the previously distributed version of VMS (14). In the present study, we evaluated the ability of BMS and VMS to identify a broad panel of yeasts of medical interest.One hundred ninety-seven isolates from different human samples, previously identified by conventional biochemical techniques or by sequencing the internal transcribed spacer 1 (ITS1) and ITS2 regions, were blindly identified using the two systems. In order to minimize the risk of misidentification related to the use of incomplete and error-filled public databases (15), the sequences obtained were compared to reference data available in two databases: GenBank, searched by using the nucleotide BLAST tool (blast.ncbi.nlm.nih.gov), and the CBS (Centraalbureau voor Schimmelcultures) yeast database (www.cbs.knaw.nl). The panel included 157 (79.7%) isolates belonging to 30 Candida or Candida-related species (Table 1), and 40 (20.3%) isolates belonging to 15 non-Candida species (Table 2). Before processing for MS identification, each isolate was cultured on Sabouraud dextrose (Kima, Padua, Italy) agar and incubated for 24 h at 35°C. For BMS, proteins were extracted as recommended by the manufacturer. Briefly, a loopful of yeasts was suspended in one volume of water and three volumes of absolute ethanol, and after centrifugation, the pellets were processed with an equal amount of formic acid and acetonitrile ...

Advantages of Using Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry as a Rapid Diagnostic Tool for Identification of Yeasts and Mycobacteria in the Clinical Microbiological Laboratory

“…In our study, the species-level identification rates for Candida species for the two MS systems were comparable to those in recent studies (25,27). However, the identification rate for non-Candida yeasts was lower than that in another study performed in Europe (27).…”

“…However, the identification rate for non-Candida yeasts was lower than that in another study performed in Europe (27). This may be due to the differences in the protein extraction steps used in the two studies, and further investigations should be focused on the proper extraction method needed for non-Candida yeasts.…”

“…The use of matrixassisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for the rapid identification of clinical yeast and mycobacterial isolates has been evaluated in some studies (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25). However, there has been a limited number of direct comparison studies focusing on the performance of the two MALDI-TOF systems to rapidly identify yeast and mycobacterial clinical isolates (26)(27)(28).…”

Comparision of matrix-assisted laser desorption ionization-time of flight (MALDI-TOF MS) with API ID 32C and VITEK 2 for the identification of Trichosporon species

“…Son dönemlerde MALDI-TOF MS, rutin mikrobiyoloji laboratuvarında mikroorganizmaların tanımlanmasında güvenilir sonuç vermesi, hızlı ve kolay uygulanması ve maliyetinin düşük olması nedeniyle umut veren bir sistem olarak ortaya çıkmıştır (7) .…”

MALDI-TOF MS for the Diagnosis of Infectious Diseases

“…Rosenvinge et al showed that the Biotyper system identified 88% of 200 yeast isolates to the species level using on-plate formic acid testing and a species cutoff of Ն1.700 (40 ). Mancini et al compared the Biotyper system (library v3.0) with protein extraction and Vitek MS (v1.2.0) with on-plate formic acid testing for the identification of 197 yeast isolates (41 ). The rate of correct identifications at the species level was comparable using the commercial databases (90% vs 84%) and improved to 100% using the Biotyper system with an in-housedeveloped database.…”