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

Cox CR, Jensen KR, Saichek NR, Voorhees KJ - Sci Rep (2015)

Bottom Line: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has emerged as a rapid approach for clinical bacterial identification.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.In addition, several pathogens were misidentified by protein profiling as non-pathogens and vice versa.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO 80401.

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.

No MeSH data available.


Related in: MedlinePlus

Comparison of protein and CeO2-catalyzed fatty acid mass spectral profiling. Representative protein (a-c) and CeO2-catalyzed FA spectra (d-f) of E. coli K12 and Shigella boydii ATCC 9207, A. baumannii ATCC 17976 and A. calcoaceticus 75.53, and L. monocytogenes ATCC 19115 and L. innocua ATCC 33090, respectively.
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f2: Comparison of protein and CeO2-catalyzed fatty acid mass spectral profiling. Representative protein (a-c) and CeO2-catalyzed FA spectra (d-f) of E. coli K12 and Shigella boydii ATCC 9207, A. baumannii ATCC 17976 and A. calcoaceticus 75.53, and L. monocytogenes ATCC 19115 and L. innocua ATCC 33090, respectively.

Mentions: Representative FA and protein spectra for bacteria that were misidentified by the Biotyper are shown in Fig. 2. Without knowledge of the proprietary Biotyper software architecture it is uncertain, but it appears that minor protein peaks are not considered and that the major peaks are too similar for a distinction to be made. As examples, comparison of spectra of E. coli K12 and S. boydii ATCC 9207 (Fig. 2a) showed the same four major protein peaks leading to the misidentification of S. boydii as E. coli. Despite the fact that A. calcoaceticus 75.53 was misidentified as A. baumannii, comparison of the protein spectra for these two strains appear visually quite different (Fig. 2b). The largest protein peaks in the spectra of L. monocytogenes ATCC 13932 and L. innocua ATCC 33090 (Fig. 2c) are nearly identical, with only small differences in intensity. In cases where correct assignments for other species were observed (data not shown), major differences were required in the protein distributions for correct ID.


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

Cox CR, Jensen KR, Saichek NR, Voorhees KJ - Sci Rep (2015)

Comparison of protein and CeO2-catalyzed fatty acid mass spectral profiling. Representative protein (a-c) and CeO2-catalyzed FA spectra (d-f) of E. coli K12 and Shigella boydii ATCC 9207, A. baumannii ATCC 17976 and A. calcoaceticus 75.53, and L. monocytogenes ATCC 19115 and L. innocua ATCC 33090, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507139&req=5

f2: Comparison of protein and CeO2-catalyzed fatty acid mass spectral profiling. Representative protein (a-c) and CeO2-catalyzed FA spectra (d-f) of E. coli K12 and Shigella boydii ATCC 9207, A. baumannii ATCC 17976 and A. calcoaceticus 75.53, and L. monocytogenes ATCC 19115 and L. innocua ATCC 33090, respectively.
Mentions: Representative FA and protein spectra for bacteria that were misidentified by the Biotyper are shown in Fig. 2. Without knowledge of the proprietary Biotyper software architecture it is uncertain, but it appears that minor protein peaks are not considered and that the major peaks are too similar for a distinction to be made. As examples, comparison of spectra of E. coli K12 and S. boydii ATCC 9207 (Fig. 2a) showed the same four major protein peaks leading to the misidentification of S. boydii as E. coli. Despite the fact that A. calcoaceticus 75.53 was misidentified as A. baumannii, comparison of the protein spectra for these two strains appear visually quite different (Fig. 2b). The largest protein peaks in the spectra of L. monocytogenes ATCC 13932 and L. innocua ATCC 33090 (Fig. 2c) are nearly identical, with only small differences in intensity. In cases where correct assignments for other species were observed (data not shown), major differences were required in the protein distributions for correct ID.

Bottom Line: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has emerged as a rapid approach for clinical bacterial identification.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.In addition, several pathogens were misidentified by protein profiling as non-pathogens and vice versa.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO 80401.

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.

No MeSH data available.


Related in: MedlinePlus