Intrinsic catalase dot blot immunoassay for identification of Mycobacterium tuberculosis, Mycobacterium avium, and Mycobacterium intracellulare.

The heat-labile T class of mycobacterial catalase exhibits peroxidase activity with some substrates. Most species of mycobacteria produce T-catalase, which is serologically characterized by a combination of shared epitopes and unique, species-specific epitopes. Antibodies to T-catalases from Mycobacterium tuberculosis, Mycobacterium avium, and Mycobacterium intracellulare have been cross absorbed with T-catalases from heterologous species and applied as dots to nitrocellulose membranes. When these membranes were incubated with crude sonic extracts of 93 strains of mycobacteria that produce sufficient T-catalase, and were then exposed to 3,3'-diaminobenzidine peroxidase substrate, only those extracts made from one of the three species represented yielded a discrete brown dot at the site of the corresponding globulin. The sensitivity of the test was at least 96.5%, and the specificity was in excess of 99.5%.