Daily supplementation with Lactobacillus reuteri DSM 17938 to extremely preterm infants modulated the gut microbiota during the first month of life in a randomised placebo-controlled trial. PROPEL-16S amplicon

Extremely low birth weight (ELBW; <1000 g) preterm infants often develop severe clinical complications such as necrotising enterocolitis, sepsis and growth failure, which may be reduced by probiotic supplementation. The aim of this study was to investigate how the supplementation with Lactobacillus reuteri DSM 17938 affected the gut microbiota composition in ELBW infants. 134 ELBW infants born before post-menstrual week (PMW) 28 were enrolled in a randomised, double-blind, placebo-controlled trial, and supplemented with L. reuteri or placebo from birth to PMW36. Stool samples were collected weekly during the first month of life, at PMW36, and at two years of age. The bacterial composition in 558 stool samples was characterized by 16S amplicon sequencing. Our results show that the microbiota composition differed between the two groups during the first month of life, with higher bacterial richness and diversity in the probiotic group. At one week of age, the differences were mainly explained by higher relative abundance of Enterobacteriacea and Staphylococcacea in the placebo group, and higher relative abundance of L. reuteri in the probiotic group. From two weeks of age the differences were mainly explained by a higher relative abundance of L. reuteri in the probiotic group. At PMW36 and two years of life there were no differences in the gut microbiota composition. In conclusion, daily supplementation of L. reuteri in ELBW preterm infants modulated the gut microbiota composition, with increased bacterial diversity and high abundance of the supplemented strain during the first month of life in the probiotic group.