Effect of aging on the mode of Mycobacterium intracellulare infection

Effect of aging on the mode of Mycobacterium intracellulare infection was examined using female ddy strain mice of 6, 12, 24, 48, 64 and 80 weeks old. When mice were infected intravenously with M. intracellulare 31F093 (8 x 10(7] and the incidence and the degree of gross lesions in the lungs and viable number of the organisms in the lungs and spleen were studied at 8 weeks after bacterial challenge, there was no marked difference in the grade of pathological lesions by age. However, all the mice younger than 25-weeks of age survived over the period of 8 weeks after infection, whereas about 30% of mice older than 48-weeks of age died during the course of infection. Thus, it is thought that some parts of old mice were more susceptible to M. intracellulare infection than young mice on the basis of their survival.