J Clin Microbiol. 2017 Jan 4. pii: JCM.01990-16. doi: 10.1128/JCM.01990-16. [Epub ahead of print]

Improved Differentiation of Streptococcus pneumoniae and Other S. mitis group Streptococci by MALDI Biotyper Using an Improved MALDI Biotyper Database Content and a Novel Result Interpretation Algorithm.

Harju I1, Lange C2, Kostrzewa M2, Maier T2, Rantakokko-Jalava K3, Haanperä M4.

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Reliable distinction of Streptococcus pneumoniae and viridans group streptococci is important because of the different pathogenic properties of these organisms. Differentiation between S. pneumoniae and closely related S. mitis species group streptococci has always been challenging, even when using such modern methods as 16S rRNA gene sequencing or matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry. In this study, a novel algorithm combined with an enhanced database was evaluated for the differentiation between S. pneumoniae and mitis species group streptococci. One hundred and one clinical mitis species group streptococcal strains and 188 clinical S. pneumoniae strains were identified both by the standard MALDI Biotyper database alone and combined with a novel algorithm. The database update from 4613 strains to 5627 strains drastically improved the differentiation of S. pneumoniae and mitis species group streptococci: when using the new database version containing 5627 strains, only one of the 101 mitis species group isolates was misidentified as S. pneumoniae whereas 66 of them were misidentified as S. pneumoniae using the old 4613 MALDI Biotyper database version. The updated MALDI Biotyper database combined with the novel algorithm showed even better performance, producing no misidentifications of the mitis species group strains as S. pneumoniae All S. pneumoniae strains were correctly identified as S. pneumoniae with both the standard MALDI Biotyper database and the standard MALDI Biotyper algorithm combined with the novel algorithm. The use of this new algorithm would thus enable reliable differentiation between pneumococci and other mitis species group streptococci using MALDI Biotyper.

Copyright © 2017 American Society for Microbiology.

PMID: 28053215 DOI: 10.1128/JCM.01990-16

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