Performance of the Vitek MS v2.0 system in distinguishing Streptococcus pneumoniae from nonpneumococcal species of the Streptococcus mitis group.

The Vitek MS v2.0 matrix-assisted laser desorption ionization-time of flight mass spectrometry system accurately distinguished Streptococcus pneumoniae from nonpneumococcal S. mitis group species. Only 1 of 116 nonpneumococcal isolates (<1%) was misidentified as S. pneumoniae. None of 95 pneumococcal isolates was misidentified. This method provides a rapid, simple means of discriminating among these challenging organisms.