Shigella sonnei O-Antigen Inhibits Internalization, Vacuole Escape, and Inflammasome Activation

Abstract

Diarrheal disease remains the second leading cause of death in children under five. Shigella remains a significant cause of diarrheal disease with two species, S. flexneri and S. sonnei , causing the majority of infections. S. flexneri are well known to cause cell death in macrophages, which contributes to the inflammatory nature of Shigella diarrhea. Here, we demonstrate that S. sonnei causes less cell death than S. flexneri due to a reduced number of bacteria present in the cell cytosol. We identify the O-Ag polysaccharide which, uniquely among Shigella spp., is present in two forms on the bacterial cell surface as the bacterial factor responsible. Our data indicate that S. sonnei differs from S. flexneri in key aspects of infection and that more attention should be given to characterization of S. sonnei infection.