Figure 3.

MtrB is required to establish active infection in mice. A and B, survival of the WT M. tuberculosis or ΔmtrB strains in the lungs (A) or spleen (B) of mice after aerosol infection with ∼100 bacilli/lung. Error bars represent S.D. and the means of cfu obtained with four animals per strain from one experiment. ***, p < 0.001; *, p < 0.05. C, sizes of the spleens from two individual mice infected with either WT or ΔmtrB for 14 weeks. Scale, 3 cm. Images are representative of one experiment with four animals per strain. D, histopathology of lung sections collected after 12 weeks of infection with the indicated strains. Sections were stained with hematoxylin and eosin and observed under a light microscope at 40× magnification. G denotes granuloma (red arrow), and AS (black arrow) denotes alveolar space. Images are representative of one experiment with four animals per strain. Scale bar, 10 μm.