Abstract
With the growing demand for sheep, the sheep farming industry has developed rapidly. However, lamb diarrhea, a disease with high mortality rates, significantly hampers the industry's growth. Traditional antibiotic treatments often disrupt the Intestinal microbiota, induce antibiotic resistance, and cause adverse side effects, highlighting the urgent need to develop alternative therapies. Bacteroides fragilis, a candidate next-generation probiotic, has been closely associated with intestinal health. This study investigated the growth characteristics and probiotic effects of a sheep-derived Bacteroides fragilis isolate, focusing on its efficacy in alleviating lamb diarrhea and infectious intestinal diseases. The experiments demonstrated that the Bacteroides fragilis isolate grows well under mildly acidic conditions (pH 6-8), exhibits some tolerance to bile salts, and has survival rates of 38.89% and 92.22% in simulated gastric and intestinal fluids, respectively, indicating its potential as a probiotic. In a mouse model, Bacteroides fragilis intervention significantly alleviated colonic inflammation caused by Enterohemorrhagic Escherichia coli infection, enhanced tight junction protein expression, mitigated oxidative stress, and improved intestinal barrier function, with high-dose interventions showing superior effects. In lamb trials, Bacteroides fragilis intervention stopped diarrhea in four out of five lambs, partially restored intestinal microbiota diversity, and reduced the abundance of potential pathogens such as Aerococcus suis and Corynebacterium camporealensis. Therefore, Bacteroides fragilis exhibited remarkable effects in regulating intestinal homeostasis, alleviating inflammation, and promoting recovery from diarrhea.