Cell-Free Spent Media Obtained from Bifidobacterium bifidum and Bifidobacterium crudilactis Grown in Media Supplemented with 3'-Sialyllactose Modulate Virulence Gene Expression in Escherichia coli O157:H7 and Salmonella Typhimurium

Pauline Bondue; Sébastien Crèvecoeur; François Brose; Georges Daube; Marie-Christine Seghaye; Mansel W Griffiths; Gisèle LaPointe; Véronique Delcenserie

doi:10.3389/fmicb.2016.01460

Cell-Free Spent Media Obtained from Bifidobacterium bifidum and Bifidobacterium crudilactis Grown in Media Supplemented with 3'-Sialyllactose Modulate Virulence Gene Expression in Escherichia coli O157:H7 and Salmonella Typhimurium

Front Microbiol. 2016 Sep 22:7:1460. doi: 10.3389/fmicb.2016.01460. eCollection 2016.

Authors

Pauline Bondue¹, Sébastien Crèvecoeur¹, François Brose¹, Georges Daube¹, Marie-Christine Seghaye², Mansel W Griffiths³, Gisèle LaPointe³, Véronique Delcenserie¹

Affiliations

¹ Department of Food Science, Fundamental and Applied Research for Animal and Health, Faculty of Veterinary Medicine, University of Liège Liège, Belgium.
² Department of Pediatrics, University Hospital Liège-Notre-Dame des Bruyères Belgium.
³ Canadian Research Institute for Food Safety, University of Guelph Guelph, Canada.

Abstract

Complex oligosaccharides from human milk (HMO) possess an antimicrobial activity and can promote the growth of bifidobacteria such as Bifidobacterium bifidum and Bifidobacterium longum subsp. 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 and B. crudilactis, a species of bovine origin, is able to metabolize some of those complex carbohydrates. This study focused on the ability of B. bifidum and B. crudilactis to 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 of Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium. Both strains were able to grow in presence of 3'SL, but B. crudilactis showed the best growth (7.92 ± 0.3 log cfu/ml) compared to B. bifidum (6.84 ± 0.9 log cfu/ml). Then, CFSM were tested for their effects on virulence gene expression by ler and hilA promoter activity of luminescent mutants of E. coli and S. Typhimurium, respectively, and on wild type strains of E. coli O157:H7 and S. Typhimurium using RT-qPCR. All CFSM resulted in significant under expression of the ler and hilA genes for the luminescent mutants and ler (ratios of -15.4 and -8.1 respectively) and qseA (ratios of -2.1 and -3.1) for the wild type strain of E. coli O157: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 observed in vitro will be further investigated regarding the overall phenotype of pathogenic agents and the exact nature of the active molecules.

Keywords: 3′-sialyllactose; Bifidobacterium bifidum; Bifidobacterium crudilactis; Escherichia coli enterohemorragic O157:H7; Salmonella enterica serovar Typhimurium; bovine milk oligosaccharide; virulence expression; whey.