The sialylated fraction of milk oligosaccharides is partially responsible for binding to enterotoxigenic and uropathogenic Escherichia coli human strains.

Milk oligosaccharides can act as soluble receptors that block bacterial adhesion to the different epithelia. Colonization factor antigens (CFA)/I- and CFA/II-expressing enterotoxigenic Escherichia coli (ETEC) strains constitute one of the main causes of diarrhea in infants. Here, the inhibition of hemagglutination mediated by these strains by milk oligosaccharides was tested. Human milk oligosaccharides showed a strong inhibitory capacity, which decreased when the oligosaccharides were desialylated. Because milk oligosaccharides also are present in the urine of neonates receiving mothers' milk, their ability to bind two uropathogenic Escherichia coli (UPEC) strains was also examined. UPEC strains expressing P (Pap) and P-like (Prs) fimbriae are responsible for infections of the urinary tract such as pyelonephritis and cystitis. The hemagglutination mediated by these strains was inhibited by human milk oligosaccharides. The sialylated fraction was partially responsible for this inhibition in the case of the UPEC expressing the P-like fimbria because differences were found after desialylation. Although bovine milk oligosaccharides were less efficient at inhibiting the hemagglutination of ETEC strains, they were still quite good inhibitors of UPEC strains.