Comparative evaluation of two matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) systems for the identification of clinically significant yeasts

• Evaluate the performance of two MALDI-TOF MS for identification of yeast compared to VITEK II.
• Accurate identification by VITEK II system, VITEK MS and Bruker-Biotyper MS was 94.1, 93.0 and 92.6%, respectively.
• 3 isolates were not identified by VITEK MS while 9 C. orthopsilosis were misidentified as C. parapsilosis.
• 11 isolates were not identified or wrongly identified by Bruker-Biotyper.
• 14 isolates were correctly identified by Bruker-Biotyper but with unreliable score of <1.7.

SummaryObjectivesTo prospectively evaluate the performance of two matrix-assisted laser desorption/ionization time-of-flight mass spectrometry systems (MALDI-TOF MS) for the identification of clinically significant yeast isolates compared to the VITEK 2 system.MethodsOne hundred and eighty-eight consecutive yeast isolates were analyzed by Bruker Biotyper and VITEK MS. The results were compared with the conventional VITEK 2 yeast identification system. Discrepant results were resolved by direct sequencing of rDNA.ResultsAccurate identification by VITEK 2, VITEK MS, and Bruker Biotyper MS was 94.1% (177/188), 93.0% (175/188), and 92.6% (174/188), respectively. Three isolates were not identified by VITEK MS, while nine Candida orthopsilosis were misidentified as Candida parapsilosis, as this species is not present in its database. Eleven isolates were not identified or were wrongly identified by Bruker Biotyper and although another 14 were correctly identified, the score was unreliable at <1.7.ConclusionThe overall accuracy of rapid MALDI-TOF MS systems was essentially comparable to that of the conventional VITEK 2 yeast identification system. However, future expansion of the databases may further improve the outcome and accuracy of identification of yeast species.