title: Cell-Free Spent Media Obtained fromBifidobacterium bifidumandBifidobacterium crudilactisGrown in Media Supplemented with 3'-Sialyllactose Modulate Virulence Gene Expression inEscherichia coliO157:H7 andSalmonellaTyphimurium.
abstract: Complex oligosaccharides from human milk (HMO) possess an antimicrobial activity and can promote the growth of bifidobacteria such asBifidobacterium bifidumandBifidobacterium longumsubsp.infantis. In addition, fermentation of carbohydrates by bifidobacteria can result in the production of metabolites presenting an antivirulence effect on several pathogenic bacteria. Whey is rich in complex bovine milk oligosaccharides (BMO) structurally similar to HMO andB. crudilactis, a species of bovine origin, is able to metabolize some of those complex carbohydrates. This study focused on the ability ofB. bifidumandB. crudilactisto grow in a culture medium supplemented in 3'-sialyllactose (3'SL) as the main source of carbon, a major BMO encountered in cow milk. Next, the effects of cell-free spent media (CFSM) were tested against virulence expression ofEscherichia coliO157:H7 andSalmonella entericaserovar Typhimurium. Both strains were able to grow in presence of 3'SL, butB. crudilactisshowed the best growth (7.92 ± 0.3 log cfu/ml) compared toB. bifidum(6.84 ± 0.9 log cfu/ml). Then, CFSM were tested for their effects on virulence gene expression bylerandhilApromoter activity of luminescent mutants ofE. coliandS. Typhimurium, respectively, and on wild type strains ofE. coliO157:H7 andS. Typhimurium using RT-qPCR. All CFSM resulted in significant under expression of thelerandhilAgenes for the luminescent mutants andler(ratios of -15.4 and -8.1 respectively) andqseA(ratios of -2.1 and -3.1) for the wild type strain ofE. coliO157:H7. The 3'SL, a major BMO, combined with some bifidobacteria strains of bovine or human origin could therefore be an interesting synbiotic to maintain or restore the intestinal health of young children. These effects observedin vitrowill be further investigated regarding the overall phenotype of pathogenic agents and the exact nature of the active molecules.
authors.affiliation: Department of Food Science, Fundamental and Applied Research for Animal and Health, Faculty of Veterinary Medicine, University of Liège Liège, Belgium.
authors.forename: Pauline
authors.initials: P
authors.lastname: Bondue
authors.affiliation: Department of Food Science, Fundamental and Applied Research for Animal and Health, Faculty of Veterinary Medicine, University of Liège Liège, Belgium.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Crèvecoeur
authors.affiliation: Department of Food Science, Fundamental and Applied Research for Animal and Health, Faculty of Veterinary Medicine, University of Liège Liège, Belgium.
authors.forename: François
authors.initials: F
authors.lastname: Brose
authors.affiliation: Department of Food Science, Fundamental and Applied Research for Animal and Health, Faculty of Veterinary Medicine, University of Liège Liège, Belgium.
authors.forename: Georges
authors.initials: G
authors.lastname: Daube
authors.affiliation: Department of Pediatrics, University Hospital Liège-Notre-Dame des Bruyères Belgium.
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Seghaye
authors.affiliation: Canadian Research Institute for Food Safety, University of Guelph Guelph, Canada.
authors.forename: Mansel W
authors.initials: MW
authors.lastname: Griffiths
authors.affiliation: Canadian Research Institute for Food Safety, University of Guelph Guelph, Canada.
authors.forename: Gisèle
authors.initials: G
authors.lastname: LaPointe
authors.affiliation: Department of Food Science, Fundamental and Applied Research for Animal and Health, Faculty of Veterinary Medicine, University of Liège Liège, Belgium.
authors.forename: Véronique
authors.initials: V
authors.lastname: Delcenserie
keywords: 3′-sialyllactose; Bifidobacterium bifidum; Bifidobacterium crudilactis; Escherichia coli enterohemorragic O157:H7; Salmonella enterica serovar Typhimurium; bovine milk oligosaccharide; virulence expression; whey