FIG. 2.

Growth of nine different M. tuberculosis strains in the spleens of BCG-vaccinated and naïve mice. Mice were sacrificed at 4, 12, and 20 weeks following a 200-CFU aerogenic challenge with each of these M. tuberculosis isolates. 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 (closed squares) mice 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.