Figure 4

Francisella cell-to-cell dissemination in J774A.1 macrophages. Cells were infected for 48 h with wild-type F. novicida constitutively expressing plasmid-borne GFP (WT-GFP). Intracellular multiplication was followed by video-microscopy (20×). Different types of bacterial release from an infected cell are illustrated. (A) Pyroptosis: infected cells explode and release free bacteria in the extra-cellular medium; or (B,C) Cell-to-cell transfer (by cellular clustering, and “Kiss and run” spread, respectively).