Background Preventing Salmonella infection and colonization in young birds is key to improving poultry gut health and reducing Salmonella contamination of poultry products and decreasing salmonellosis for human consumption (eggs and meat). Probiotics can improve poultry health. The present study was conducted to investigate the impact of a probiotics, Enterococcus faecium NCIMB11181 ( E. faecium NCIMB 11181) on the intestinal mucosal immune responses, microbiome and barrier function in the presence or absence of Salmonella Typhimurium ( S. Typhimurium, ST) infection.
Methods Two hundred and forty 1-day old Salmonella -free male broiler chickens (Arbor Acres AA + ) were randomly allocated to four groups with 6 replicate cages of 10 birds each. The four experimental groups were follows: (1) negative control (NC), (2) S. Typhimurium challenged positive control (PC), (3) the E. faecium NCIMB 11181-treated group (EF), (4) the E. faecium NCIMB 11181-treated and S. Typhimurium challenged group (PEF).
Results Results indicated that, although continuous feeding E. faecium NCIMB 11181 did not obviously alleviate growth depression caused by S. Typhimurium challenge ( P >0.05), E. faecium NCIMB 11181 addition significantly lessened intestinal inflammation by competitively blocking Salmonella intestinal colonization and inhibiting TLR4 -medicated immune inflammatory responses through upregulating intestinal mucosa Tollip mRNA levels ( P < 0.05). Moreover, supplemental E. faecium NCIMB 11181 to the infected chickens remarkably attenuated gut morphological structure damage and decreased intestinal cell apoptosis as evidenced by increasing gut villous height, and reducing Salmonella translocation and intestinal TUNEL-positive cell numbers ( P < 0.05). Also, E. faecium NCIMB 11181 administration notably enhanced humoral immunity through promoting the production of anti- Salmonella specific antibodies in intestinal mucosa and serum of the infected birds ( P < 0.05). Additionally, 16S rRNA sequencing analysis revealed that E. faecium NCIMB 11181 supplementation ameliorated S. Typhimurium infection-induced gut microbial dysbiosis by enriching Lachnospiracease and A listipes levels, and suppressing Barnesiella abundance. Predicted function analysis (PICRUSt) indicated that the functional genes of cecal microbiome involved in C5-branched dibasic acid metabolism; valine, leucine and isoleucine biosynthesis; glycerolipid metabolism and lysine biosynthesis were enriched; while alanine, asparate and glutamate metabolism; MAPK signal pathway-yeast; ubiquine and other terpenoid-quinore biosynthesis, protein processing in endoplasmic reticulum; as well as glutathione metabolism were suppressed by E. faecium NCIMB 11181 supplementation.
Conclusion Collectively, our data suggested that dietary E. faecium NCIBM 11181 supplementation could ameliorate S. Typhimurium infection-induced gut injury in broiler chickens. Our findings also suggest that E. faecium NCIMB 11181 may serve as an effective non-antibiotic feed additive for improving gut health and immune defense to Salmonella infection. Keywords: Broiler chickens, Enterococcus faecium , Gut health, Salmonella