Fig. 3.
Macrophage replication and cytotoxicity assays reveal a class of Francisella virulence factors. Bone marrow-derived macrophages were infected with 10 bacteria per macrophage of the indicated bacterial strains. (A) Cells were lysed and bacteria were collected at 10 h after infection and plated for enumeration. (B and C) Macrophages were activated with heat-killed F. novicida for 12 h before infection. Cell death was quantified by LDH release at 7 (B) or 6 (C) h after infection. Data are representative of three independent experiments. Statistical significance as compared with wild-type: ∗, P < 0.05; ∗∗∗, P < 0.0005.