Performance evaluation of a new matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, ASTA MicroIDSys system, in bacterial identification against clinical isolates of anaerobic bacteria

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been introduced for bacterial identification. The ASTA MicroIDSys system (ASTA, Suwon, Korea) is a new MALDI-TOF MS system developed for species identification of microorganisms. We evaluated the performance of MicroIDSys against clinical isolates of anaerobic bacteria. A total of 370 non-duplicated clinical isolates of anaerobic bacteria were tested in this study. Bacterial identification with MicroIDSys was performed with a direct smear method, and measured spectra were analyzed using respective software. The results of MicroIDSys were compared with the results of Bruker Biotyper and 16S rRNA sequencing. The overall agreement rates for the 370 clinical isolates (34 genera and 99 species) were 95.4% (353/370) at the genus level and 91.6% (n = 340) at the species level. Only 17 isolates were incorrectly identified at the genus level: five misidentifications and 12 unidentifications. The MicroIDSys system exhibited excellent performance in the identification of clinically relevant bacterial species. Most of the Bacteroides isolates (98.0%, 99/101) and all of the Clostridium difficile (100%, n = 11), Clostridium perfringens (100%, n = 10), Finegoldia magna (100%, n = 11), and Parvimonas micra (100%, n = 10) isolates were correctly identified at the species level. The MicroIDSys system proved useful in the identification of anaerobic bacteria, especially clinically relevant species. This system could be of use in clinical microbiology laboratories as a primary tool for identifying anaerobic bacteria. •The performance of MicroIDSys system for the anaerobic bacterial identification was evaluated with clinical isolates.•The MicroIDSys showed reliable performance for identifying clinically relevant anaerobes such as Bacteroides and Clostridium.•Rarely encountered anaerobic pathogens were not correctly identified due to the size and quality of database.•The identification accuracy needs to be further increased by updating the databases.