SMALL INTESTINE Early interactions of Salmonella enterica serovar typhimurium with human small intestinal epithelial explants

Background: Salmonella enterica serovar typhimurium (S typhimurium) causes invasive gastroenteritis in humans, a disease involving significant penetration of the intestinal mucosa. However, few studies have been undertaken to investigate this interaction directly using differentiated human gut tissue. Aims: To investigate the early interactions of an enteropathogenic strain of S typhimurium with human intestinal mucosa using human intestinal in vitro organ culture (IVOC). Methods: Wild-type and mutant derivatives of S typhimurium TML were used to compare interactions with cultured human epithelial cells, bovine ligated loops, and human intestinal IVOC. Results: S typhimurium TML was shown to attach to cultured Caco-2 brush border expressing cells and cause tissue damage and fluid accumulation in a ligated bovine loop model. S typhimurium TML bound predominantly to the mucus layer of human IVOC explants during the first four hours of IVOC incubation. From four to eight hours of IVOC incubation, small but characteristic foci of attaching and invading S typhimurium TML were detected as clusters of bacteria interacting with enterocytes, although there was no evidence for large scale invasion of explant tissues. Ruffling of enterocyte membranes associated with adherent Salmonella was visualised using electron microscopy. Conclusions: Human IVOC can be used as an alternative model for monitoring the interactions between S typhimurium and human intestinal epithelium, thus potentially offering insight into the early stages of human Salmonella induced gastroenteritis.