Figure 7.

Attenuation of F. novicida Δ1212–1218 in mice. Mice were inoculated with 1000 CFU of wild-type F. novicida and F. novicida Δ1212–1218 IN, followed by euthanasia on days 1, 3, 6, 10, and 14. The bacterial burden in the lungs (A), spleen (B), and liver (C) were determined by viable plate counts. The bars represent the mean bacterial burden ± the SEM for F. novicida (dotted bar) and F. novicida Δ1212–1218 (checkered bar). All mice inoculated with F. novicida (•) needed to be euthanized by day 3. All mice inoculated with F. novicida Δ1212–1218 cleared the bacterial infection by day 10–14 (D). F. novicida Δ1212–1218 (■) was attenuated in mice IN at a dose of at least 10,000 CFU and infection caused minimal to no signs of clinical illness.