Rapid chemotaxonomy of pathogenic bacteria using in situ thermal hydrolysis and methylation as a sample preparation step coupled with a field-portable membrane-inlet quadrupole ion trap mass spectrometer

A field-portable, pyrolysis membrane-inlet quadrupole ion trap mass spectro meter has been used to characterize four pathogenic bacteria (Bacillus anth racis, Brucella melitensis, Yersinia pestis, and Francisella tularensis). M oreover, a variety of strains were included, prepared under various growth conditions and a range of growth stages. In these analyses, an in situ ther mal hydrolysis-methylation procedure was used during pyrolysis with the rea gent tetramethylammonium hydroxide. Mass spectra generated from the analysi s of the four pathogens contained information related to the biochemical co mposition of the sample (i.e. biomarkers) including mass spectral peaks der ived from methyl esters of fatty acids, DNA/RNA, and peptide/protein fragme nts. Using multivariate statistics, bacterial mass spectral fingerprints we re analyzed to determine the variance in the data and the contribution of b iomarker origin (i.e. lipid, protein, nucleic acid, etc.) for bacterial dif ferentiation. An optimum 98.3% correct classification rate was obtained usi ng cross validation with linear discriminant analysis (on four replicates e ach of 54 bacterial samples) using only biomarkers of lipid origin and the bacterial spore biomarker dipicolinic acid, (Int J Mass Spectrom 190/191 (1 999) 331-342) (C) 1999 Elsevier Science B.V.