Classification and identification of Mycobacterium africanum by pyrolysis mass spectrometry

Pyrolysis mass spectrometry was used to classify and identify strains of Mycobacterium africanum and of M. tuberculosis, M. bovis and M. bovis BCG. The multicharacter mass pyrograms were evaluated by computerized data handling procedures that were suited for classification and identification. The results revealed considerable heterogeneity among the African strains, which was shown to be linked to the geographic distribution of the strains. On the basis of a routine mass spectrometric identification key the African strains were identified without exception as belonging to, what is referred to as the 'Tuberculosis complex' (i.e. the clinically relevant group formed by strains of M. Tuberculosis, M. bovis and M. bovis BCG). Classification of the strains by means of discriminant analysis indicated an intermediate clustering for the majority of the African strains and overlap for some African strains with in particular M. bovis. It was concluded that from the mass spectrometric data a species status for the group of African strains was not justifiable.