Vitek MS matrix-assisted laser desorption ionization-time of flight mass spectrometry for identifying respiratory bacterial pathogens: a fast and efficient method.

Mass spectrometry has become a reference resource for identifying microorganisms in clinical microbiology services. One hundred and fifty one clinical isolates were selected from respiratory specimens routinely identified as Streptococcus pneumoniae (43), Haemophilus influenzae (64) and Moraxella catarrhalis (44). These identifications were compared with other phenotypical methods and mass spectrometry (MALDI-TOF-MS Vitek). Result discrepancies were assessed by 16S rRNA sequencing. Thirty-eight of the 43 strains of S. pneumoniae (86%) were identified as such using phenotypical methods and spectrometry. In 5 cases, MALDI-TOF identified 4 of them as Streptococcus pseudopneumoniae and 1 as S. mitis/oralis. Forty-eight of the 64 strains were identified as H. influenzae (75%) using biochemical identification systems and automated identification systems, whereas MALDI-TOF-MS Vitek identified 51 strains (79%) as such. Conventional methods and spectrometry identified all the 40 strains tested (100%) as M. catarrhalis. All strains with discrepant results were sequenced, and in all cases, the identification obtained by spectrometry was confirmed. The results obtained in this study show that mass spectrometry provides identification of these bacteria faster and in a more reliable way than those based on conventional phenotypical methods.