Chronic Aerogenic Tuberculosis in Mice

Aerogenic tuberculous infection of mice with small numbers of tubercle bacilli resulted in chronic tuberculosis which persisted in some of the animals for over a year. The lesions produced by this infection contained a constant number (“steady state”) of culturable units of tubercle bacilli after 8 weeks, but there was enlargement and coalescence of the lesions because of an increased number of foam cell macrophages. In conse-sequence, there was an increased involvement of normal lung tissue. Thirty-six to 52 weeks after infection, the number of culturable units of tubercle bacilli had increased beyond that of the steady state; deaths continued to occur during this period.