Development and Validation of In-house Database for MALDI-TOF MS‒based Yeast Identification Using a Fast Protein Extraction Procedure

In recent studies evaluating the usefulness of the matrix-assisted laser desorption ionization‒time of flight mass spectrometry (MALDI-TOF MS)-based identification of yeasts for the routine diagnosis, the preanalytical sample processing was emerged as a critical step for reliable MALDI-TOF MS outcomes, especially when the Bruker Daltonics Biotyper software was used. In addition, inadequate results often occurred due to the discrepancy between methods used for clinical testing and database construction. Therefore, we created an in-house MALDI-TOF MS library using the spectra from 156 reference and clinical yeast isolates (48 species in 11 genera), that were generated with a fast sample preparation procedure. After a retrospective validation study, our database was evaluated on 4,232 yeasts, routinely isolated during a 6-month period and fast prepared for MALDI-TOF MS analysis. Thus, 4,209 (99.5%) isolates were successfully identified to the species level (scores of ≥2.0), with 1,676 (39.6%) having scores higher than 2.3. For the remaining 23 (0.5%) isolates, no reliable identification (score of