LAUSR

Objectives: To compare the impact of two probiotic supplements on fecal microbiota and metabolites, as well as on gut inflammation in human milk-fed preterm infants. Methods: In this single-center observational cohort study, we assessed the effects of Bifidobacterium longum subsp. infantis or Lactobacillus reuteri supplementation on the infant gut microbiota by 16S rRNA gene sequencing and fecal metabolome by 1H nuclear magnetic resonance spectroscopy. Fecal calprotectin was measured as a marker of enteric inflammation. Aliquots of human or donor milk provided to each infant were also assessed to determine human milk oligosaccharide (HMO) content. Results: As expected, each probiotic treatment was associated with increased proportions of the respective bacterial taxon. Fecal HMOs were significantly higher in L. reuteri fed babies despite similar HMO content in the milk consumed. Fecal metabolites associated with bifidobacteria fermentation products were significantly increased in B. infantis supplemented infants. Fecal calprotectin was lower in infants receiving B. infantis relative to L. reuteri (P < 0.01, Wilcoxon rank-sum test) and was negatively associated with the microbial metabolite indole-3-lactate (ILA). Conclusions: This study demonstrates that supplementing an HMO-catabolizing Bifidobacterium probiotic results in increased microbial metabolism of milk oligosaccharides and reduced intestinal inflammation relative to a noncatabolizing Lactobacillus probiotic in human milk-fed preterm infants. In this context, Bifidobacterium may provide greater benefit in human milk-fed infants via activation of the microbiota-metabolite-immune axis.