A study of the relationship between Nocardia and Mycobacterium diernhoferi--a typical fast growing Mycobacterium.

An antigenic analysis by immunodiffusion has been performed on representative strains of Nocardia asteroides, N. brasiliensis, N. caviae, N. uniformis and Mycobacterium diernhoferi. The findings have been related to those previously reported for mycobacteria. The 4 nocardial species were found to be internally homogeneous but antigenically distinct from each other. They possessed the Groups I and III antigens of mycobacteria and a group of 3 antigens shared among themselves alone. Thus, nocardiae are antigenically more closely related to the fast growing mycobacteria than to the slow growing mycobacteria. Mycobacterium diernhoferi was found to be a typical fast growing mycobacterium possessing 3 serotypes distinguishable by minor differences in the Group IV (species specific) antigens.