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Updated: Dec 5, 2025

Identification of Rare Bacterial Pathogens by 16S rRNA Gene Sequencing and MALDI-TOF MS
Published on: July 11, 2016
Identification of Streptococcus dysgalactiae using matrix-assisted laser desorption/ionization-time of flight mass
Eirik Jovall Nybakken1, Oddvar Oppegaard2, Marianne Gilhuus3
1Department of Microbiology, P.b. 1400, Haukeland University Hospital, 5021, Bergen, Norway.
Abstract:
Matrix-assisted laser desorption/ionization time of flight (MALDI-ToF) has revolutionized bacterial identification. However, the phylogenetic resolution is still insufficient for discerning several β-haemolytic streptococcal species. We aimed to improve the diagnostic performance of MALDI-ToF through manual curation of the reference spectra in Brukers Compass Library DB-7854. Before intervention, only 133 out of 217 (62%) Streptococcus dysgalactiae isolates were successfully identified to the species level, 83 isolates were identified to the genus level as either S. dysgalactiae, S. pyogenes or S. canis, and one S. dysgalactiae isolate was wrongly identified as S. canis. All 109 S. canis isolates were successfully identified to the species level. Removal of three reference spectra from the database significantly improved the identification of S. dysgalactiae to 94%, without compromising identification of S. canis. This illustrates the advantage of refinement of the reference database in order to improve the analytic precision of MALDI-ToF.
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