Stability of bacteriophage type of Mycobacterium tuberculosis: absence of variation caused by experimental chemotherapy in mice and analysis of spontaneous variation.

The bacteriophage typing of 54 strains isolated from the tissues of mice infected with the strain H37Rv of Mycobacterium tuberculosis and treated with isonazid and rifampin showed that the bacteriophage type did not change. The fluctuation analysis of populations of the tubercle bacilli demonstrated that the rate of mutation from sensitivity to resistance in respect to the bacteriophage DS6A was less than 1.3 X 10(-8) mutations per bacterium per generation.