FIG. 1.

Bacterial burdens in lungs of NOS2^−/− (closed circles) and wild-type C57BL/6 (open circles) mice following intravenous infection with M. tuberculosis Erdman (A) or clinical isolate CI3 (B), CI4 (C), or CI7 (D). Mice were infected with 10⁵ to 10⁶ CFU of M. tuberculosis, and lung homogenates were plated at the times indicated to determine the number of viable bacilli. Each point is the mean of three mice, and the bar is the standard error and is representative of two experiments. By 4 weeks postinfection and beyond, the bacterial burden in the lungs of NOS2^−/− mice is significantly greater than that of wild-type C57BL/6 animals for all of the M. tuberculosis strains examined (P < 0.05).