The predominant milk oligosaccharide 6′-sialyllactose reduces the internalisation of Pseudomonas aeruginosa in human pneumocytes

Pseudomonas aeruginosa is an opportunistic pathogen, often responsible for nosocomial infections and chronic lung infections in cystic fibrosis patients. The antibiotic resistance associated with this pathogen makes it difficult to eradicate. Therefore, the discovery of molecules capable of reducing the morbidity and mortality associated with this infection is appealing. P. aeruginosa pathogenicity is associated with both adhesion and invasion of epithelia. Previous studies have shown that predominant milk oligosaccharides, 6′-sialyllactose (6-SL) and 3′-sialyllactose (3-SL), are able to inhibit P. aeruginosa adhesion to human pneumocytes. Here, we demonstrate that 6-SL, at its estimated systemic concentrations i.e. what infants are likely to ingest during breastfeeding, is effective in reducing the pneumocytes invasion of both P. aeruginosa mucoid and non mucoid strains, the effect being concentration-dependent in the case of the latter. This study shows the potential of milk oligosaccharides as ingredients in functional foods aimed at lowering the incidence of infectious diseases.