Figure 2. N. meningitidis induces meningitis in the absence of bacteremia.

10⁷ CFU of the bioluminescent FAM20 strain was given i.n. to CD46 transgenic mice (CD46^+/+). Mice were observed using an IVIS imaging system and blood samples were take from the tail vein once per day. Mice challenged with PBS were set as uninfected control. (A) At day 4 post-infection, distinct bioluminescent signals were detected in the brain area of an infected CD46^+/+ mouse, which had a lethal outcome. The presence of N. meningitidis in the CNS was confirmed by viable counts after plating serial diluted CSF sample on GC agar plates. The number of bacteria identified in the CSF and blood (CFU/ml) are presented. N.D., not detected. (B) Brain tissue was collected from mice and stained for N. meningitidis as described in Materials and Methods. Bacterial signals (red) were found on meningeal cells (right panel, arrowheads) of infected mice. No bacterial staining was found in the corresponding regions (left panel) of uninfected mice.