Characterization of invasion pattern of Shigella flexneri in the small intestine of infant mice

Abstract

Shigella spp. invades the large intestinal epithelium and promotes a strong inflammatory response in humans. A recent study revealed that 4‐day‐old mice were infected with invasive Shigella strains but not 5‐day‐old mice. We therefore attempted to clarify the underlying mechanism that induces inflammation in the small intestine of infant mice but not of adult mice. Balb/c mice of different ages were orally administered 5 × 109 CFU of Shigella flexneri 5a (M90T) strain and analyzed for colonization and physiopathological features. Unexpectedly, we found that 4‐, 7‐, and 14‐day‐old mice, but not 21‐day‐old mice, showed tissue destruction and PMN infiltration in the small intestine at 6 h following Shigella infection, mimicking human shigellosis. Interestingly, Shigella mainly invaded epithelial cells and crypt region but not the M cells in the small intestine. Further, high numbers of Shigella were mainly colonized in the lamina propria but not in Peyer's patches in the small intestine, and the Shigella colonization gradually decreased with ageing. We are now attempting to determine the crucial signaling mechanism of Shigella infection in the epithelium and crypt region of the small intestine of infant mice.