Cytotoxicity of Shigella dysenteriae 1 for cultured mammalian cells.

The cytotoxicity of an invasive toxigenic wild-type strain of Shigella dysenteriae 1 (3818T) was compared with that of noninvasive, toxigenic strain 38180 and hypotoxigenic strain 725. Cytolysis of HeLa or Henle 407 cells exposed to these strains was measured by release of (3H) uridine from prelabeled monolayers. HeLa cells exposed to noninvasive, toxigenic strain 38180, or to partially purified Shiga toxin were lysed only after a latent period of more than 8 hr. During this period, protein synthesis was inhibited. In contrast, Henle 407 cells that were exposed to strain 38180 or to exogenous Shiga toxin were unaffected. When either Henle 407 or HeLa cells were infected with invasive toxigenic strains, rapid lysis ensued. Quantitative microassay of cytosol toxicity showed that Shiga toxin was produced intracellularly by strain 3818T. The data suggest that cytolysis of infected mammalian cells is caused, at least in part, by intracellular Shiga toxin.