Invasion and survival of M. tuberculosis pknD mutant in host-derived cells. A. BALB/c mice were infected with M. tuberculosis CDC1551 or pknD mutant, and sacrificed at days 1 and 49 after infection. The mutant for M. tuberculosis pknD was significantly attenuated (P = 0.004) in mouse brain, but not lung tissue, 49 days after infection. No defect was observed in the lungs at either time point. Bacterial burden is represented as log10 CFU/organ for all animal experiments. B. Invasion of host-cell monolayers by wild-type CDC1551, wild-type intergenic transposon control, pknD transposon mutant (pknD:Tn), and pknD genetic complement (pknD:Comp) was examined and normalized to the wild-type control. Invasion assays were performed in brain microvascular endothelial cells (HBMEC), epithelial A549 cells, and umbilical vein endothelia (HUVEC). No difference in invasion was observed in A549 cells (P = 0.31) or HUVEC (P = 0.41). A significant reduction in invasive capacity, however, was observed in the CNS-derived HBMEC (P = 0.02). This defect was restored by genetic complementation with the native pknD/pstS2 operon. N.S. = not significantly different. C. Intracellular survival of each of the above M. tuberculosis strains was examined in HBMEC at days 1, 3, 5, and 7 after infection. The pknD:Tn mutant demonstrated an invasion and intracellular survival defect in HBMEC relative to wild-type over the course of the seven day infection. D. Survival was also examined by infection of activated J774 macrophages. No corresponding survival defect for the pknD:Tn mutant was observed in these cells during the seven day infection. A mutant for the gene Rv0442c, known to be attenuated in the macrophage model, is included as a control. All CFU counts are represented as mean ± standard deviation.
Be et al. BMC Microbiology 2012 12:7 doi:10.1186/1471-2180-12-7