In vivo clearance of the dal dat ΔactA 142 strain in WT (left) and GKO−/− (right) mice (A) and the dal dat 142 strain in WT mice (B). Mice were immunized intraperitoneally with 2 × 106 CFU of the dal dat 142 strain and 108 CFU of the dal dat ΔactA 142 strain. The bacterial load in the organs, livers, and spleens were determined after days 1, 2, 3, 7, and 10 of immunization. Two mice from each group were sacrificed on different days, and the number of bacterial CFU was determined by plating several dilutions of the homogenized spleens and livers on BHI plates containing 100 μg/ml of streptomycin. The plates were incubated at 37°C for 24 to 48 h for bacterial growth. Columns, mean number of CFU from each mouse; bars, standard deviation (SD).