A rapid method for identification of Mycobacterium species by polyacrylamide gel electrophoresis of soluble cell proteins.

The sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles of an easily and rapidly prepared soluble protein fraction were used in conjunction with conventional techniques to identify different strains of Mycobacterium tuberculosis, M. bovis, M. bovis BCG, M. africanum, M. avium, M. kansasii, M. marinum, M. gastri, M. simiae and M. malmoense. Complete concordance of results from both methods was obtained with all species except those of the M. tuberculosis complex. With the SDS-PAGE technique, all strains of the M. tuberculosis complex were recognised as belonging to one species. By visual analysis of the SDS-PAGE polypeptide profiles, only minor differences between strains of the same species were seen and each species showed a characteristic polypeptide profile. Quantitation of the data by calculation of the Dice coefficient of similarity of the band positions obtained by densitometry indicated that the similarity between different strains of one species was 90-100% and the similarity between the species was in the range 30-45%. The results indicate that SDS-PAGE is a simple and rapid method for identifying mycobacterial strains.