The tuberculous diseases originating from different species of acid-fast bacilli

Disease due to the typical human type tubercle bacillus is rapidly diminishing as a result of public health measures and specific chemotherapy. Lesions in man resulting from other kinds of acid-fast bacilli are now being recognized in increasing numbers. Some of these bacilli had been seen before but were confused with typical M. hominis, others were considered to be harmless saprophytes, while others could not be found with the methods used. Special culture media, different conditions for cultivation, new physical, chemical and biological tests, and inoculation into a variety of animal hosts are now available. With their use more than a dozen different strains of human type tubercle bacilli, and more than a score of other species of acid-fast bacilli may now be distinguished. A simple chemical test readily separates the human type tubercle bacilli from all other kinds of acid-fast bacilli. The differentiation of the different human and animal pathogenic acid-fast bacilli from the avirulent saprophytes and other harmless mycobacteria presents great difficulties, but methods are becoming available which usually make this possible. Since the distinction may be of great therapeutic and epidemiologic importance, the effort should be made.