Sequestration of Mycobacterium tuberculosis in tight vacuoles in vivo in lung macrophages of mice infected by the respiratory route

Following aerosol infection of mice with Mycobacterium tuberculosis, single mycobacteria or pairs of bacilli were observed within individual phagocytic vacuoles bound by tightly apposed vacuolar membranes. The virulent organism was not observed free in the cytoplasm of the parasitized cells or in the extracellular space of the lung granulomata. This study indicates that in vivo, virulent mycobacteria survive and probably replicate within a unique tight vacuole in the infected phagocyte within the lung.