Evaluation of the VITEK® MS PRIME system for routine identification of bacteria, yeasts, and molds in a tertiary care hospital laboratory

Purpose: Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) is integral to routine microbial identification. This study examines the performance of the VITEK® MS PRIME (bioMérieux; “PRIME”) system for identification of clinically relevant bacteria, yeasts, and molds. Methods: We evaluated PRIME using the in vitro diagnostic (IVD) knowledge base version 3.2 (KB3.2) database on 652 clinical isolates, with reference identifications by polymerase chain reaction (PCR) and DNA sequencing. We also compared PRIME results with those obtained using the MALDI Biotyper (Bruker Daltonics; “Biotyper”) for bacteria and yeasts in our routine workflow. Results: PRIME correctly identified 311/317 bacteria (98.1%), 185/196 yeasts (94.4%), and 112/130 molds (86.2%); non-identification for molds was 16/130 (12.3%), with 2/130 (1.5%) misidentifications. Biotyper achieved 308/317 (97.2%) correct identifications for bacteria and 120/196 (61.2%) for yeasts with the IVD database; using the research use only (RUO) database increased the identification rate to 184/196 (93.9%) and reduced non-identifications from 76/196 (38.8%) to 12/196 (6.1%) for yeasts. Misidentifications by PRIME were uncommon, whereas molds—assessed only with PRIME—showed more frequent non-identification and occasional cross-taxon assignments. For example, Fusarium solani was reported as Rhizopus arrhizus, reflecting persistent challenges in MALDI-TOF MS for filamentous fungi and the impact of database breadth. Notably, mold performance observed here lies near the upper range of recent PRIME evaluations using IVD KB3.2. Conclusions: Overall, PRIME provided reliable routine identification for bacteria, yeasts, and molds; further expansion of fungal reference spectra and optimization of extraction workflows should improve mold identification. Pending such improvements, possible non-identifications or discordant assignments should be adjudicated by conventional microbiology before reporting.