MALDI-TOF mass spectrometry for differentiation between Streptococcus pneumoniae and Streptococcus pseudopneumoniae.

We compared the Vitek MS and Microflex MALDI-TOF mass spectrometry platform for species differentiation within the Streptococcus mitis group with PCR assays targeted at lytA, Spn9802, and recA as reference standard. The Vitek MS correctly identified 10/11 Streptococcus pneumoniae, 13/13 Streptococcus pseudopneumoniae, and 12/13 S. mitis/oralis. The Microflex correctly identified 9/11 S. pneumoniae, 0/13 S. pseudopneumoniae, and 13/13 S. mitis/oralis. MALDI-TOF is a powerful tool for species determination within the mitis group. Diagnostic accuracy varies depending on platform and database used.