Mutation of the galU gene does not attenuate infectivity of FT in vivo. C57BL/6 mice (4/group) were infected intranasally with 5 × 104 CFU (50 × LD50 for FT LVS) of either the WT or galU mutant strain of FT LVS. Organs were harvested at 24, 48, 72 and 96 hours p.i. and CFU/g of organ was determined for lungs, liver, and spleen. The lower limit of detection was 20 CFU/g. Statistical analyses were performed via two-way ANOVA with a Bonferroni multiple comparisons post test and all significant differences are indicated as follows: ** P < 0.01 and *** P < 0.0001. The data shown is representative of two independent experiments of similar design.