Inhibition of bacterial adhesion and salmonella infection in BALB/c mice by sialyloligosaccharides and their derivatives from chicken egg yolk

The effects of an egg-yolk-derived sialyloligosaccharide (YDS), asialo-YDS, and a sialylglycopeptide of YDS (SGP) on bacterial adhesion to intestinal epithelial cells and on Salmonella infection in BALB/c mice were examined. YDS, its derivative asialo-YDS, and SGP strongly inhibited the binding of Salmonella enteritidis but not E. coli K-88 to a human epithelial cell line, Caco-2. In a Salmonella infection experiment using BALB/c mice, oral administration of these reagents effectively prevented the bacteria from proliferating in spleen, as well as preventing lethality. An experiment using radioactive SGP orally administered to mice revealed that the compound was absorbed from the intestine into blood and eliminated via urine within 8 h. However, these reagents did not influence the production of TNF-alpha or NO. in culture macrophages. The results suggest that they inhibit Salmonella infection not by activating macrophages but by inhibiting the entry of bacteria through the gut, suggesting that YDS and its derivatives are useful for preventing Salmonella infection when ingested continuously.