Jin Zhou

The gut microbiota is known to regulate the immune system and thereby influence susceptibility to infection. In this study, we observed that the administration of Enterococcus faecium HDRsEf1 (HDRsEf1) led to an improvement in the development of the immune system. This was evidenced by an increase in both the spleen index and the area of spleen white pulp. Specifically, the proportion of T helper (Th) 1 cells and the production of IFN-γ and IL-12 were significantly increased in the spleens of mice treated with HDRsEf1. In agreement with the in vivo results, we found that Th1-related cytokines, including IFN-γ and IL-12p70, were strongly induced in splenocytes treated with HDRsEf1. In addition, Th1 cell activation and high-level secretion of IL-12p70 were also confirmed by coculture of CD4⁺ T cells with bone marrow-derived dendritic cells treated with HDRsEf1. Moreover, the employment of HDRsEf1 was identified to augment resilience against systemic infection provoked by S. Typhimurium and stimulate the expression of the genes for TNFα and iNOS in the initial stage of infection, signifying that reinforced Th1 cells and IL-12 might activate macrophages for antibacterial safeguards. In summary, our study suggests that HDRsEf1 could act as an effective immunobiotic functional agent, promoting systemic Th1 immunological responses and priming defenses against infection.

Enterococcus faecium HDRsEf1 (HDRsEf1) was identified to reduce the incidence of diarrhea in weaned piglets, but the mechanism has not been elucidated yet. Based on the fact that gut microbiota plays a crucial role in regulating inflammatory responses, the effects of HDRsEf1 on microbiota across the intestinal tract in weaned piglets were investigated. Microbiota from the luminal contents and the mucosa of the ileum, cecum, and colon of HDRsEf1-treated piglets were explored by 16S rRNA sequencing and qPCR. It was demonstrated that microbiota in different gut niches responded specifically to HDRsEf1, with major alterations occurring in the ileum and cecum. The total bacterial load of microbiota in ileal luminal contents and the relative abundance of Escherichia-Shigella in the ileal mucosa was significantly down-regulated by HDRsEf1 administration, while the relative abundance of butyrate-producing bacteria (including Clostridiaceae-1, Rumencoccidae, and Erysipelotrichaceae) in cecal luminal contents was significantly up-regulated. Moreover, the utilization of HDRsEf1 improved intestinal morphological development and reduced the inflammatory response, which were negatively correlated with the relative abundance of Escherichia-Shigella in the ileal mucosa and butyrate-producing bacteria in cecal luminal contents, respectively. Collectively, this study suggests that the administration of HDRsEf1 alters gut microbiota, thereby alleviating inflammation and improving intestinal morphological development in weaned piglets.