A head-to-head comparison of three MALDI-TOF mass spectrometry systems with 16S rRNA gene sequencing.

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Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has revolutionized diagnostics in culture-based microbiology. Commonly used MALDI-TOF MS systems in clinical microbiology laboratories are MALDI Biotyper (Bruker Daltonics) and Vitek MS (bioMérieux), but recently the new EXS2600 (Zybio) has been launched. This study aimed to evaluate the performance of the three devices by comparing the results to 16S rRNA gene sequencing. A set of 356 previously collected difficult-to-identify bacteria was tested in parallel with the three systems. Only the direct smear method and simple formic acid extraction were applied. Valid results were achieved for 98.6%, 94.4%, and 93.3% of all isolates by MALDI Biotyper, EXS2600, and Vitek MS, respectively. Of all valid results, agreement with sequencing data was achieved in 98.9%, 98.5%, and 99.7% by MALDI Biotyper, EXS2600, and Vitek MS, respectively. Considering only the isolates with valid measurements at the single-species level, misidentification rates were 0%, 2.6%, and 1.1% for MALDI Biotyper, EXS2600, and Vitek MS, respectively. Apart from minor performance differences, our data demonstrate that the three systems provide comparable results and are suitable for use in medical diagnostic laboratories.