FIG. 5.

Mycobacterial growth in I/St and A/Sn macrophages following in vitro infection. Peritoneal (A) and lung (B) macrophages were prepared, plated, and infected as described above. The rate of mycobacterial growth was measured by [³H]uracil uptake at different time points after cocultures were established. [³H]uracil (1 μCi/well) was added for the last 18 h of incubation. The wells containing mycobacteria alone at numbers corresponding to each MOI served as controls. The results obtained in one of eight similar 60-h experiments are expressed as mean counts per minute (CPM) ± SD for triplicate cultures, and statistically significant (P < 0.01; Mann-Whitney U test) interstrain differences are marked with asterisks. Consistent results were obtained in 84- and 108-h experiments (data not shown).