Effects of Bacteroides fragilis and Enterococcus faecium Administration as Probiotic Candidates: Impact on Growth Performance, Organ Indices, and Gut Microbiota Balance in Mice

Abstract

This research was conducted to evaluate the safety and effects of two probiotic candidate strains, <i>Enterococcus faecium</i> (<i>E. faecium</i>) and <i>B. fragilis</i> (<i>BF</i>), which were isolated from healthy sheep, on various factors such as intestinal structure, growth performance, organ indices, and gut microbiota in female C57BL/6J mice. A total of fifty mice were categorized into five groups: <i>BF108</i>, <i>BF109</i>, <i>EF108</i>, <i>EF109</i>, and a control group. The results indicated that mice in the <i>EF108</i> and <i>BF109</i> groups experienced a significant increase in body weight by day 28 compared to the control group (<i>p</i> < 0.05). Additionally, the liver index in the <i>BF108</i> and <i>EF108</i> groups was significantly lower (<i>p</i> < 0.05) than that of the control group. The length of the colon was also significantly greater (<i>p</i> < 0.05) in the <i>EF109</i> and <i>BF109</i> groups relative to the control group. According to the linear discriminant analysis effect size (LEfSe), the presence of probiotics led to an increased relative abundance of <i>Pediococcus acidilactici</i> in the <i>EF109</i> and <i>BF109</i> groups, while <i>Lactiplantibacillus plantarum</i> was the most prevalent strain in the <i>EF108</i> and <i>BF108</i> groups. Finally, Spearman correlation analysis demonstrated a positive association between Bacillota and <i>Bacteroidota</i> as well as Verrucomicrobiota. Additionally, <i>Bacteroidota</i> displayed positive relationships with Verrucomicrobiota and <i>Planctomycetota</i>, while showing a negative correlation with <i>Actinomycetota</i> and <i>Gemmatimonadota</i>, supporting its potential use as next-generation probiotics. In summary, our results indicate probiotics may have a role in promoting intestinal health by enhancing intestinal shape and histological characteristics.