Strain-level bacterial identification by CeO2-catalyzed MALDI-TOF MS fatty acid analysis and comparison to commercial protein-based methods

• Published in: Scientific reports 2015-07, Vol.5 (1), p.10470-10470, Article 10470
• Main Authors: Cox, C. R., Jensen, K. R., Saichek, N. R., Voorhees, K. J.
• Format: Article
• Language: English
• Subjects: 631/326/2522; 692/53/2421; 9/10; Bacteria; Bacteria - classification; Bacteria - metabolism; Bacterial Proteins - metabolism; Catalysis; Cerium; Desorption; Fatty acids; Fatty Acids - metabolism; Humanities and Social Sciences; Ionization; Ions; Lasers; Lipids; Listeria; Mass spectrometry; Mass spectroscopy; Metabolomics - methods; multidisciplinary; Pathogens; Principal components analysis; Proteins; Proteomics - methods; Reproducibility of Results; Science; Species; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep10470

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has emerged as a rapid approach for clinical bacterial identification. However, current protein-based commercial bacterial ID methods fall short when differentiating closely related species/strains. To address this shortcoming, we employed CeO 2 -catalyzed fragmentation of lipids to produce fatty acids using the energy inherent to the MALDI laser as a novel alternative to protein profiling. Fatty acid profiles collected from Enterobacteriaceae , Acinetobacter and Listeria using CeO 2 -catalyzed metal oxide laser ionization (MOLI MS), processed by principal component analysis and validated by leave–one-out cross-validation (CV), showed 100% correct classification at the species level and 98% at the strain level. In comparison, protein profile data from the same bacteria yielded 32%, 54% and 67% mean species-level accuracy using two MALDI-TOF MS platforms, respectively. In addition, several pathogens were misidentified by protein profiling as non-pathogens and vice versa. These results suggest novel CeO 2 -catalyzed lipid fragmentation readily produced (i) taxonomically tractable fatty acid profiles by MOLI MS, (ii) highly accurate bacterial classification and (iii) consistent strain-level ID for bacteria that were routinely misidentified by protein-based methods.