Application of pyrolysis mass spectrometry to the classification and identification of mycobacteria

Application of modern pyrolysis techniques offers the possibility for mass spectrometric analysis of complete bacterial cells. It was shown that pyrolysis mass spectra provide fingerprints of mycobacterial cells that are characteristic on the (sub)species level. Computer-aided comparisons of the spectra for mycobacteria were used for identification of unknown strains as members of either the "tuberculosis complex" (Mycobacterium tuberculosis, Mycobacterium bovis-BCG, M. bovis) or of the group referred to as "atypical mycobacteria." Pyrolysis mass spectrometry was performed with a completely automated instrument, and spectra were evaluated by two computerized numerical methods. The first method has general applicability to mass spectrometry data, while the second was devised for the routine identification of the "tuberculosis complex." With use of the latter method, 125 strains were identified. A positive correlation of 94.4% was found between the results of this method and the results of the usual bacteriologic procedures; 1.6% of all strains were given a falsely negative identification, and 4.0% were given a falsely positive identification.