Bifidobacterium longum subsp. infantis B8762 modulates the infant gut-lung axis via microbial and metabolic...

Respiratory and gastrointestinal infections are leading causes of morbidity in children. Increasing evidence highlights the gut-lung axis as a key regulatory interface influencing infection susceptibility. Bifidobacterium longum subsp. infantis B8762 (B8762) has shown clinical efficacy in reducing such infections, but its mechanistic basis remains unclear. In a randomized, double-blind, placebo-controlled study involving 115 infants (probiotic group: n = 57, placebo group: n = 58; aged 6-12 months), fecal metagenomic sequencing was performed to assess microbial and functional changes after four weeks of B8762 supplementation (0.5 × 10¹⁰ CFU/day). B8762 significantly altered the gut microbial structure (β-diversity, P < 0.05) without affecting α-diversity. The intervention enriched beneficial taxa including Bifidobacterium longum, Eubacterium limosum, and Roseburia hominis, while reducing potential pathogens such as Staphylococcus aureus and Candida parapsilosis (P < 0.05). Functionally, B8762 upregulated metabolic pathways involved in coenzyme A and L-tryptophan biosynthesis and enhanced predicted production of immunoregulatory metabolites including butyrate, inosine, and chenodeoxycholic acid. In summary, this study suggests that B8762 modulates the pediatric gut microbiota toward a composition and metabolic profile that supports mucosal barrier integrity and systemic immune regulation. These findings provide mechanistic insight into its protective role against respiratory and gastrointestinal infections in children, supporting its use as a targeted gut-lung axis probiotic intervention.