A Synbiotic of Bifidobacterium animalis subsp. lactis BB-12 and 2′-FL Alleviate Infant Diarrhea and Anxiety-like Behaviors via Gut Microbiota Modulation in an EPEC O127 Infection Model

Background/Objectives: Infant diarrhea is a major global cause of morbidity and mortality. WhileBifidobacteriumis linked to diarrhea, its preventive effects, underlying mechanisms, and potential synergistic benefits with prebiotics remain unclear. The objective of this study was to explore the efficacy of a synbiotic composed ofBifidobacterium animalissubsp.lactisBB-12 (BB-12) and 2′-fucosyllactose (2′-FL) in alleviating infant diarrhea.Methods: One-week-old C57BL/6J mice were used to construct a model of infant diarrhea via infection with enteropathogenicEscherichia coli(EPEC) O127. Mice were administered BB-12 (108CFU per mouse), 2′-FL (1 g/kg), or their combination (synbiotic) for three consecutive weeks.Results: Administration of the synbiotic not only markedly improved diarrhea, anxiety-like behavior, colon inflammation, and gut barrier function but also positively reshaped the microbial community. This was achieved through a significant rise in short-chain fatty acid (SCFA)-producing bacteria (e.g.,AkkermansiaandParaprevotella), a rise in fecal SCFAs, and a reduction in harmful bacteria such asEscherichia.Conclusions: The synbiotic effectively relieves EPEC-induced infant diarrhea by regulating gut microbiota composition and metabolic functions. These findings highlight its potential as a dietary intervention in infant diarrhea and provide new insights into infant health applications.