Targeting the gut-lung axis by synbiotic feeding to infants in a randomized controlled trial

Synbiotics may modulate gut microbiota and prevent infections. In a randomized controlled trial (NCT01625273) infants weaned from breast milk were fed formula with prebiotics (fructo- and galactooligosaccharides) or the same prebiotic formula with Lactobacillus paracasei ssp. paracasei strain F19 (synbiotics) from 1 until 6 months of age. The objective was to examine synbiotic effects on gut microbiota maturation. Fecal samples collected at ages 1, 4, 6 and 12 months (324 samples for microbial and 197 samples for metabolic characterization) were analyzed. We demonstrate enrichment of Bifidobacterium and increases in antimicrobial metabolites derived from microbial fermentation of phenylalanine and pectins in the synbiotic group. The gut microbiota of infants with lower respiratory tract infections (LRTI) were depleted of Lactobacillales but enriched in Klebsiella species and associated antimicrobial resistance genes. These compositional and functional changes of the gut microbiota may be linked to the previously reported reduction of LRTI in the synbiotic group.