MALDI-TOF analysis

Genome-sequenced clinical isolates provided a well-characterized sample set to develop matrix-assisted linear desorption/ionisation-time-of-flight mass spectrometry (MALDI-TOF MS) spectra for use in clinical lab speciation of subsequent patient isolates. Analyses were performed on the VITEK® MS (bioMerieux, Marcy-L’Etoile, France). Isolates were cultured on 5% sheep’s blood agar plates (Remel) and analyzed after 24 h incubation at 37°C and 5% CO₂. Individual colonies were analyzed in duplicate by MALDI-TOF MS with α-Cyano-4-hydroxycinnamic acid as the matrix, and identified using FDA-approved IVD 2.0 database or Knowledge Base 2.0 database. Isolates were also analyzed in research use only mode and identified using the Saramis 3.0 database. The averaged mass spectra plots were plotted using Graphpad Prism software (GraphPad, LaJolla, CA).