FIG. 1.

Growth of nine different M. tuberculosis strains in the lungs of BCG-vaccinated and naïve mice. Mice were challenged with about 200 CFU of each of these M. tuberculosis isolates and then were sacrificed 4, 12, and 20 weeks postchallenge to determine pulmonary bacterial burdens. To determine the aerosol infection dose, groups of mice were also sacrificed at 4 h postchallenge. The results are representative of two to three experiments. Significant differences between the numbers of lung CFU for vaccinated (open circles) and control mice (closed squares) are shown with asterisks. *, P < 0.05; **, P < 0.01; and ***, P < 0.001. In these studies, the ChS, HN878, N4, and NHN5 strains are Beijing (B) lineage strains.