Comparison of Splenic CFUs between RB51 and B. abortus ΔpurD mutant mice groups.  Clearance of the RB51 and  B. abortus ΔpurD mutant in mice. Recovery of viable bacterial CFUs count from spleens of mice at 10th and 20th DPI. Results are expressed as total CFU per spleen. Error bars represent average values ± the standard deviations. The asterisks denote values that are significantly different (*P <0.05) between groups with the parent RB51 and the B. abortus ΔpurD mutant at each time point, as determined by two way ANOVA.