Osmotically sensitive Brucella in infected normal and immune macrophages.

When Brucella suis is grown in tissue cultures of normal guinea pig macrophages, the Brucella multiplies significantly without the induction of osmotically sensitive forms. In immune macrophages in the presence of normal guinea pig serum, there is a reduction in the number of intracellular Brucella and no multiplication is seen over a 72-hr period. After 6 hr of exposure to immune macrophages, however, approximately 50% of the surviving intracellular Brucella are osmotically sensitive, i.e., they will survive and grow only on medium containing 0.2 m sucrose. Brucella grown in immune macrophages, in the presence of rabbit antiserum against whole guinea pig serum, show the presence of osmotically sensitive forms, although at a reduced level compared to the number seen with immune macrophages in normal guinea pig serum.