Intracellular Pasteurella pseudotuberculosis: Multiplication in Cultured Spleen and Kidney Cells.

Pasteurella pseudotuberculosis multiplied within rabbit cells in primary culture. Spleen cells from rabbits were either dispersed mechanically, exposed to the organism immediately after cell preparation, and grown as a pellet or the cells were dispersed enzymatically and grown as a monolayer for 4 to 6 days before the bacteria were introduced. Intracellular multiplication proceeded at a logarithmic rate for 1 to 2 days, with a generation time of about 70 min in pelleted cells and 4 to 5 hr in monolayered cells. Under the conditions employed, the wild-type virulent strain and an avirulent mutant multiplied at similar rates. Atmosphere, constituents of the medium, and multiplicity of infection influenced intracellular proliferation. The organism also proliferated in kidney cells. Microscopic observation of stained cells indicated limited growth of the pathogen in spleen cells at 37 C. In kidney cells, the pasteurellae localized in compartments; frequently, a single compartment with masses of proliferating organisms almost filled the cytoplasm.