MALDI-TOF QC study published 30 March 2021
MALDI-TOF MS is the most commonly used tool for bacterial species identification in clinical routine diagnostics. A remaining challenge in bacterial identification is mass spectra quality, which is currently only vaguely defined. In this study published in Frontiers in Cellular and Infection Microbiology, we aimed to define quantitative proxies for mass spectral quality and elaborate simple protocols to maximize these in routine diagnostics. We acquired MALDI-TOF mass spectra of 47 diverse bacterial strains under various conditions. We identify five mass spectral features as good proxies for mass spectral quality, as they are correlated with correct species identification using three different databases. These features include the number of ribosomal marker peaks and the total intensity of a spectrum. Over all isolates included in this study, we find that a young bacterial colony age, applying little bacterial material and overlaying the sample with formic acid yields the highest mass spectral quality. We show that by reliably detecting marker peaks MALDI-TOF mass spectra allows for higher resolution typing, also distinguishing between closely related species e.g. within the Klebsiella pneumoniae complex, the Staphylococcus aureus complex and within viridans streptococci.