Impact of dietary supplementation of Bacillus subtilis on the metabolic profiles and microbial ecology of weanling pigs experimentally infected with a pathogenic Escherichia coli

Background Our previous study demonstrated that dietary supplementation of Bacillus subtilis enhanced growth performance and intestinal integrity in weaned pigs challenged with enterotoxigenic Escherichia coli (ETEC). Therefore, this study aimed to explore the impact of Bacillus subtilis on gut health and its role in modulating host–microbe interactions in post-weaning pigs. Results ETEC infection disrupted key metabolic pathways in distal colon, including glutathione, beta-alanine, and pyrimidine metabolism, indicating increased oxidative stress, impaired nucleotide balance, and amino acid catabolic stress. Bacillus subtilis supplementation induced distinct metabolomic and microbiome profiles in colon digesta of weaned pigs challenged with ETEC. Bacillus subtilis -treated pigs under ETEC challenge exhibited significant enrichment in amino acid- and energy-related pathways such as arginine biosynthesis, phenylalanine metabolism, pantothenate and CoA biosynthesis. ETEC infection induced microbial dysbiosis in the distal colon, resulting in decrease ( P  < 0.05) in abundance of Streptococcaceae and Enterobacteriaceae compared to healthy controls. Bacillus subtilis supplementation mitigated the ETEC-induced disruptions by increasing the relative abundance of beneficial bacterial families, including Lachnospiraceae and Bacteroidaceae . Conclusions Supplementation of Bacillus subtilis improves intestinal health and resilience against ETEC challenge by mitigating infection-induced metabolic disruptions and gut dysbiosis in weaned pigs.