Enterococcus faecium from chicken feces improves chicken immune response and alleviates Salmonella infections: a pilot study

Lay Summary Infectious bacterial contamination in broiler production is a food safety concern and can be transmitted to humans via contaminated meat and derived products. Minimizing bacterial infections using beneficial bacteria called probiotics can reduce the emergence of antibiotic resistance in the livestock industry. In this study, we focused on improving chicken health against Salmonella infections. Beneficial probiotics were isolated from broiler chicken carcasses. Antibiotic-sensitive and antimicrobially active beneficial bacteria were identified by DNA sequencing technology and identified as Enterococcus faecium. In a further study performed in a chicken model, E. faecium-fed chickens showed improved body weight and reduced death in Salmonella-infected chickens. The S. enterica load was also lower in these E. faecium-fed chickens. Enterococcus faecium-fed chickens showed increased levels of short-chain fatty acids and reduced interleukin 1 beta, C-reactive protein, and interferon gamma levels compared to those in the S. enterica-infected chicken group. These results revealed that an E. faecium formulation could prevent bacterial infection and improve the quality of broiler chickens. Enterococcus faecium isolated from CF reduced the symptoms of Salmonella infection in broiler chickens. Enterococcus is a non-toxic, beneficial bacterium that improves the health and immune response of the host. Probiotics reduce the emergence of antibiotic resistance in the livestock industry. Chicken feces are reservoirs of beneficial microbiomes. The aim of this study was to isolate putative probiotics from the intestinal contents of broiler chickens. Five fecal samples were collected from two poultry farms in Al-Ahsa, Saudi Arabia. Of the 11 morphologically distinct isolates from chicken feces (CF) samples, five isolates displayed positive reactions to Gram staining, catalase, and oxidase tests, and reacted negatively to a hemolytic assay. The isolates CF1, CF2, CF3, CF8, and CF11 were selected for further analysis of probiotic characterization, gastric survival capacity, antibiotic susceptibility, and antimicrobial activity against poultry infected with Salmonella enterica. CF2 and CF11 showed the highest hydrophobic values (> 51% hydrophobic nature). CF1, CF2, and CF11 showed potent antimicrobial activities. The active isolate CF2 was identified as Enterococcus faecium by 16s rRNA sequencing and showed a genetic similarity of 99.1%. An in vivo study was conducted using a chicken model. Enterococcus faecium-fed chickens showed an improved body weight and a lower mortality rate (17-34%). Salmonella enterica colony-forming unit (CFU) invasion in the spleen and thymus was significantly reduced in the E. faecium-fed chickens. The fecal S. enterica load was reduced from CFU 6.8 to 3.9/g in oral-administered E. faecium-fed chickens. Enterococcus faecium-fed chickens showed increased levels (P < 0.01) of butyric acid and reduced levels (P < 0.01) of intestinal interleukin 1 beta, C-reactive protein, and interferon gamma levels compared to those in the S. enterica-infected chicken group. In addition, E. faecium showed significant binding to Caco-2 epithelial cells in vitro and inhibited S. enterica colonization, indicating co-aggregation of E. faecium in epithelial cells. These results revealed that an E. faecium formulation could prevent bacterial infection and improve the quality of broiler chickens.