Human Milk Oligosaccharides Mitigate Infant Diarrhea and Anxiety-like Behaviors via Gut Microbiota Modulation in an EPEC O127 Infection Model

Infant diarrhea remains a leading cause of morbidity and mortality worldwide. Although human milk oligosaccharides (HMOs) have been clinically linked to reduced pathogen colonization in mice, their preventive effects on infant diarrhea and the underlying mechanisms remain unclear. In this study, one-week-old diarrhea C57BL/6J mice were induced with enteropathogenic Escherichia coli O127 (EPEC O127) to establish an infant diarrhea model. Meanwhile, the mice received HMOs containing 2'-fucosyllactose (2'-FL, 1 g kg-1) and/or lacto-N-neotetraose (LNnT, 0.3 g kg-1) for three weeks. The results showed that HMOs significantly alleviated diarrhea symptoms, mitigated anxiety-like behaviors, reduced colon inflammation, and restored gut barrier integrity. Notably, HMOs reshaped the gut microbiota by increasing the relative abundance of short-chain fatty acid (SCFA)-producing bacteria (e.g., Lacrimispora), thereby elevating fecal SCFA levels while decreasing Escherichia and other harmful taxa. These findings suggest that HMOs can effectively relieve EPEC-induced infant diarrhea by modulating the composition and metabolic function of the gut microbiota. Overall, this study highlights the potential of HMOs as a dietary intervention for alleviating infant diarrhea and provides new insights into their application in infant health.