FIG. 2.

Bacterial burdens in lungs of NOS2^−/− (closed circles) and wild-type C57BL/6 (open circles) mice following aerosol infection with M. tuberculosis Erdman (A) or clinical isolate CI3 (B), CI4 (C), or CI7 (D). Mice were infected by aerosol with approximately 50 viable bacilli, and lung homogenates were plated at the times indicated to determine the number of viable bacilli. Each point is the mean of three mice (except on day 1 postinfection, when two mice were examined), and the bar is the standard error. M. tuberculosis Erdman and clinical isolate CI3 were evaluated three times with similar results. Isolates CI4 and CI7 were studied once. By 33 days postinfection and beyond, the bacillary load in the lungs of NOS2^−/− mice was significantly greater than that of wild-type C57BL/6 animals for all of the strains of M. tuberculosis tested (P < 0.05)