title: Strain-level bacterial identification by CeO2-catalyzed MALDI-TOF MS fatty acid analysis and comparison to commercial protein-based methods.
abstract: 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 CeO2-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 CeO2-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 CeO2-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.
authors.affiliation: Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO 80401.
authors.forename: C R
authors.initials: CR
authors.lastname: Cox
authors.affiliation: Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO 80401.
authors.forename: K R
authors.initials: KR
authors.lastname: Jensen
authors.affiliation: Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO 80401.
authors.forename: N R
authors.initials: NR
authors.lastname: Saichek
authors.affiliation: Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO 80401.
authors.forename: K J
authors.initials: KJ
authors.lastname: Voorhees
mesh_terms: D001419:Bacteria / Q000145:classification* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D002384:Catalysis; D002563:Cerium; D005227:Fatty Acids / Q000378:metabolism*; D055432:Metabolomics / Q000379:methods; D040901:Proteomics / Q000379:methods; D015203:Reproducibility of Results; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods
chemical_list: D001426:Bacterial Proteins; D005227:Fatty Acids; D002563:Cerium; C030583:ceric oxide