Studies on the effect of an Enterococcus faecium probiotic on T cell populations in peripheral blood and intestinal epithelium and on the susceptibility to Salmonella during a challenge infection with Salmonella Typhimurium in piglets

Although Enterococcus faecium is used as a probiotic feed supplement in animal production, feeding of the bacterium to piglets resulted in a more severe infection with Salmonella Typhimurium DT104 during a challenge experiment. To enlighten the mode of action by which E. faecium affected the piglets' health, we investigated the influence of the probiotic bacterium on the development of intestinal and circulating immune cells during a challenge experiment with S. Typhimurium DT104. To minimise varying impacts of the maternal immunity on the course of infection, only piglets were implemented that descended from Salmonella-free sows. In addition, the potency of purified blood and intraepithelial immune cells to control the growth of Salmonella was tested in vitro. In animals treated with E. faecium, a reduction of intraepithelial CD8alphabeta T cells, reduced circulating CD8alphabeta T cells and a less efficient control of intracellular Salmonella growth, mediated by peripheral blood mononuclear cells, were observed.