scholarly journals Determination of Serotypes of Shiga Toxin-ProducingEscherichia coliIsolates by Intact Cell Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry

2010 ◽  
Vol 77 (3) ◽  
pp. 896-905 ◽  
Author(s):  
Axel Karger ◽  
Mario Ziller ◽  
Barbara Bettin ◽  
Birgit Mintel ◽  
Susann Schares ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Shiga Toxin ◽  
Mass Spectra ◽  
Intact Cell ◽  
Laser Desorption ◽  
Laser Desorption Ionization ◽  
E Coli ◽  
Desorption Ionization ◽  
Matrix Assisted Laser ◽  
Matrix Assisted Laser Desorption

ABSTRACTShiga toxin-producingEscherichia coli(STEC) isolates representing the serotypes O165:H25, O26:H11/H32, and O156:H25 were analyzed by matrix-assisted laser desorption/ionization (MALDI) mass spectra of whole cells, a procedure also known as intact cell mass spectrometry (ICMS or IC-MALDI MS) or MALDI-typing. We demonstrate that within the given species the three serotypes can be well discriminated by ICMS. Conditions for the construction of serotype-specific prototypic mass spectra were systematically optimized by filtering out masses that do not contribute to the discrimination of the serotypes. Binary distances between prototypic spectra and sample spectra were used to determine serotypes of unknown samples. With parameters optimized, only 0.7% of the assignments were incorrect compared to 31% when distances were calculated from alignments of unfiltered mass spectra. Within the different serotypes, clusters of genetically relatedE. colimost probably originating from single clones could be distinguished by restriction fragment length polymorphism analysis. Since ICMS did not reproduce these clusters, we conclude that the power of ICMS is just sufficient to discriminateE. coliserotypes under certain conditions but fails for the differentiation ofE. colibelow this level.

scholarly journals Rapid Characterization of Spores of Bacillus cereusGroup Bacteria by Matrix-Assisted Laser Desorption-Ionization Time-of-Flight Mass Spectrometry

2000 ◽  
Vol 66 (9) ◽  
pp. 3828-3834 ◽  
Author(s):  
Victor Ryzhov ◽  
Yetrib Hathout ◽  
Catherine Fenselau
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectra ◽  
Time Of Flight ◽  
Laser Desorption ◽  
Laser Desorption Ionization ◽  
Desorption Ionization ◽  
Flight Mass Spectrometry ◽  
Rapid Characterization ◽  
Matrix Assisted Laser ◽  
Matrix Assisted Laser Desorption

ABSTRACT Matrix-assisted laser desorption-ionization (MALDI) time-of-flight mass spectrometry was used to characterize the spores of 14 microorganisms of the Bacillus cereus group. This group includes the four Bacillus species B. anthracis, B. cereus, B. mycoides, andB. thuringiensis. MALDI mass spectra obtained from whole bacterial spores showed many similarities between the species, except for B. mycoides. At the same time, unique mass spectra could be obtained for the different B. cereus and B. thuringiensis strains, allowing for differentiation at the strain level. To increase the number of detectable biomarkers in the usually peak-poor MALDI spectra of spores, the spores were treated by corona plasma discharge (CPD) or sonicated prior to MALDI analysis. Spectra of sonicated or CPD-treated spores displayed an ensemble of biomarkers common for B. cereus group bacteria. Based on the spectra available, these biomarkers differentiate B. cereus group spores from those of Bacillus subtilis andBacillus globigii. The effect of growth medium on MALDI spectra of spores was also explored.

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