FIG. 4.

Growth of isogenic BCG strains in THP-1-derived macrophages. THP-1 cells were forced to differentiate into macrophage-like cells with 10 nM PMA for 2 days at 37°C and then rested overnight. Monolayers were infected at a multiplicity of infection of 1 for 4 h, washed, and lysed at the indicated time points. Intracellular growth of Denmark::pGH1 (•) and Denmark::mmaA3 (□) was determined by serial dilution plating. The data shown represent the mean CFU ± standard error of the mean from an experiment repeated four times with similar results (P > 0.05).