The relationship between immunodiffusion and agglutination serotypes of Mycobacterium avium and Mycobacterium intracellulare.

Twenty Mycobacterium avium/intracellulare strains of diverse origins and two reference strains of each of Schaefer's serotypes 1-21 were examined by immunodiffusion analysis. The results produced three distinct groups, which we have called A, B and C. Two of these, A and B, appear to be variants, perhaps subspecies of M. avium, and Group C is M. intracellulare. Within each group, rough variants, untypable by Schaefer's agglutination method, were found to be antigenically identical to the smooth parent strain by immunodiffusion analysis. The results obtained were essentially in agreement with those of some previous workers based on animal pathogenicity studies, skin-test studies in sensitized guinea-pigs and DNA homology.