Interaction of Salmonella enterica serovar Typhi with cultured epithelial cells: roles of surface structures in adhesion and invasion

Abstract

In this study we investigate the ability of Salmonella enterica serovar Typhi (S. Typhi) surface structures to influence invasion and adhesion in epithelial cell assay systems. In general, S. Typhi was found to be less adherent, invasive and cytotoxic than S. enterica serovar Typhimurium (S. Typhimurium). Culture conditions had little effect on adhesion of S. Typhi to cultured cells but had a marked influence on invasion. In contrast, bacterial growth conditions did not influence S. Typhi apical invasion of polarized cells. The levels of S. Typhi, but not S. Typhimurium, invasion were increased by application of bacteria to the basolateral surface of polarized cells. Expression of virulence (Vi) capsule by S. Typhi resulted in a modest reduction in adhesion, but profoundly reduced levels of invasion of non-polarized cells. However, Vi capsule expression had no affect on invasion of the apical or basolateral surfaces of polarized cells. Mutation of the staA, tcfA or pilS genes did not affect invasion or adhesion in either the presence or the absence of Vi capsule.

Three New Lactobacillus plantarum Strains in the Probiotic Toolbox against Gut Pathogen Salmonella enterica Serotype Typhimurium

“…Since Salmonella is one of the frequent causes of infection of the digestive tract (33), we decided to use it as a test microorganism for antibacterial properties of our potentially probiotic bacteria. Salmonella species are facultative intracellular bacteria, capable of invading, surviving, and oft en multiplying within diverse eukaryotic cell types, including epithelial and phagocytic cells (21). Adhesion to the intestinal epithelial surface is a key step in pathogenesis and is central to colonisation of the intestine (34,35).…”

“…is mediated by bacterial fi mbriae which recognise certain receptors on eukaryotic cells (20). Salmonella enterica is known to adhere to and invade intestinal cells, including Caco-2 cells (21). Several studies indicate that diff erent Lactobacillus strains could inhibit the adhesion of Salmonella and some other diarrhoeagenic bacteria (Escherichia coli, Yersinia pseudotuberculosis and Listeria monocytogenes), thus reducing colonisation and preventing infection (22,23).…”

Typhi genes expressed during infection or involved in pathogenesis

“…Moreover, the model used is often different. However, Typhi is less adherent, invasive and cytotoxic than Typhimurium [4,34] suggesting that many differences are left to be discovered.…”

“…However, a Typhi strain harboring a deletion in the viaB locus was shown to be highly invasive, which can be explained by the production of the SPI-1 T3SS [23]. Similarly, by using a tviB mutant, the presence of the Vi capsule has been shown to inhibit adhesion as well as invasion of epithelial cells [34] (Table 1). SPI-11 pagC Detected in human serum [13] ISP1820 Up in THP-1 [7] pagD, envE ISP1820 Up in THP-1 [7] Adhesion tcfB Detected in human serum [13] stbD Detected in human serum [13] csgGFE Detected in human serum [13] Other SPIs.…”

SPI-7: Salmonella’s Vi-Encoding Pathogenicity Island

“…This protein, PilS, also appears to mediate the interaction with the chloride channel CFTR (Cystic Fibrosis Transmembrane Conductance Regulator) [46], which is involved in the uptake of S. Typhi into epithelial cells [47]. More recent data shows that a pilS knockout mutant does not suffer from reduced adhesion to, or invasion of, epithelial cells [48], indicating that the interaction is complex and may vary depending on the specific strain or growth conditions. In addition, the type IVB pili are implicated in increasing inflammatory response in human monocytic cells [49].…”