Infection of Cultured Mouse Macrophages with Shigella flexneri.

Virulent, avirulent, and attenuated hybrid strains of Shigella flexneri 2a are equally susceptible to phagocytosis by cultured mouse peritoneal macrophages. The virulent strain is highly lethal for the macrophages, whereas the avirulent is not and is killed. The attenuated hybrid strain is intermediate in its lethality. Comparable results were obtained by using virulent and avirulent S. flexneri 1b, 3, and 5. Destruction of macrophages occurs shortly after infection, suggesting virulent strains may possess a toxic component. The relationship of the ability to kill macrophages with multiplication of virulent shigellae in mucosal tissue is discussed.