Differentiation between T-Catalases Derived from Mycobacterium avium and Mycobacterium intracellular by a Solid-Phase Immunosorbent Assay

Abstract

Antibody to the T-catalase derived from a culture of Mycobacterium avium serovar 8 was purified by immunoaffinity absorption and elution and tested in a solid-phase immunosorbent assay against T-catalases from 31 strains in the M. avium complex. The immunologic distances from the homologous antigen exhibited a bimodal distribution. Strains of serovars 1 through 6 and 8, which correspond to the M. avium deoxyribonucleic acid (DNA) homology group of Baess, yielded immunologic distance scores against the reference serovar 8 preparation ranging from 2 to 16 U. Strains of serovars 7, 12, 14, 16, 18, and 19, which correspond to the Mycobacterium intracellulare DNA homology group, yielded immunologic distance scores ranging from 20 to 30 U. Among serovars for which DNA homology data were not available, strains of serovar 10 fell into the M. avium catalase serogroup, and serovars 13, 15, 17, 20, 23, and 25 fell into the M. intracellulare group. The status of serovar 9 was ambiguous. When the reference antibody was cross-absorbed with T-catalase from a serovar 14 strain, many of the antibodies to common epitopes were removed; the remaining antibodies reacted strongly with catalases from all strains belonging to serovars of the M. avium DNA homology group, but only minimally with catalases from strains of serovars in the M. intracellulare DNA homology group. Our results provide support for continued recognition of M. avium and M. intracellulare as separate species and for reassignment of some serovars from M. intracellulare to M. avium.