Strain-dependent effects of Bifidobacterium on loperamide-induced constipation via gut microbiota and abfA cluster.

BACKGROUND: Constipation is a common gastrointestinal disorder. Although conventional treatments can alleviate symptoms, they often cause side effects. Bifidobacterium, a safe and well-tolerated probiotic, has demonstrated potential in constipation management; however, functional variability among strains limits its broad application. RESULTS: This study investigated the efficacy of four novel Bifidobacterium strains and the commercial reference Bifidobacterium animalis subsp. lactis BB12 using a loperamide hydrochloride (LOP)-induced constipated mouse model. Bifidobacterium supplementation significantly improved constipation phenotypes, including increased fecal water content, intestinal transit rate, and fecal output, while shortening the time to first black stool. It also enhanced the intestinal barrier by up-regulating tight junction proteins, leading to reduced tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), and elevated anti-inflammatory interleukin 10 (IL-10) and fecal short-chain fatty acids (SCFAs). Bifidobacterium modulated gut microbiota composition, with B. animalis subsp. lactis C-2 notably enriching Actinobacteriota, which correlated positively with constipation relief and SCFAs, and negatively with inflammation. Moreover, the abfA cluster expression in C-1 and C-2 was similar to BB12 and higher than in other strains, which correlated with the superior performance of B. animalis strains in constipation alleviation, suggesting a potential genetic determinant warranting further functional validation. CONCLUSION: These findings reveal strain-specific mechanisms and support the targeted use of Bifidobacterium for constipation treatment. © 2026 Society of Chemical Industry.