Effect of Saccharomyces boulardii and Mode of Delivery on the Early Development of the Gut Microbial Community in Preterm Infants

Abstract

Background: Recent advances in culture-independent approaches have enabled insights into the diversity, complexity, and individual variability of gut microbial communities.

Objectives: To examine the effect of oral administration of Saccharomyces (S.) boulardii and mode of delivery on the intestinal microbial community in preterm infants.

Study design: Stool samples were collected from preterm newborns randomly divided into two groups: a probiotic-receiving group (n = 18) or a placebo group (n = 21). Samples were collected before probiotic intake (day 0), and after 2 and 6 weeks of supplementation. The composition of colonizing bacteria was assessed by 16S ribosomal RNA (rRNA) gene sequencing of fecal samples using the Ion 16S Metagenomics Kit and the Ion Torrent Personal Genome Machine platform.

Results: A total of 11932257 reads were generated, and were clustered into 459, 187, and 176 operational taxonomic units at 0 days, 2 weeks, and 6 weeks, respectively. Of the 17 identified phyla, Firmicutes Actinobacteria, Proteobacteria, and Bacteroidetes were universal. The microbial community differed at day 0 compared with at 2 weeks and 6 weeks. There was a tendency for increased bacterial diversity at 2 weeks and 6 weeks compared with day 0, and infants with a gestational age of 31 weeks or higher presented increased bacterial diversity prior to S. boulardii administration. Firmicutes and Proteobacteria remained stable during the observation period, whereas Actinobacteria and Bacteroidetes increased in abundance, the latter particularly more sharply in vaginally delivered infants.

Conclusion: While the mode of delivery may influence the development of a microbial community, this study had not enough power to detect statistical differences between cohorts supplemented with probiotics, and in a consequence, to speculate on S. boulardii effect on gut microbiome composition in preterm newborns.

Fig 1. Relative levels of bacterial DNA extracted from fecal samples in preterm infants delivered vaginally (VD) or by cesarean section (CS).

0, day 0; 2w, 2 weeks; and 6w, 6 weeks after supplementation.

Fig 2. Results of PCA analysis of infant gut microbiome in infants delivered vaginally compared with those of infants delivered by cesarean section.

Only 10 of the most abundant OTUs are shown. PC, principal component; var., variance; 0, day 0; 2w, 2 weeks; and 6w, 6 weeks after probiotic or placebo supplementation.

Fig 3. Level of abundance of most prevalent phyla in stool samples of preterm infants collected at various time points.

Samples were collected 6–12 days following birth (0w or day 0 prior to supplementation), and 2 weeks (2w), and 6 (6w) weeks after probiotic or placebo supplementation, and from healthy adults (ADULT).

Fig 4. Composition of the gut microbiome at the early phase of development dominated by four phyla: Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria.

A phylogenetic tree demonstrating bacterial abundance is present in the center. Each circle depicts a heatmap, representing a one-time probe. The more intense the color on the heatmap, is, the larger the percentage of reads from a given genus is.

Fig 5. Boxplot of community α diversity expressed by the Simpson index in stool samples collected from preterm infants at day 0 (prior to supplementation), and 2 (2w) and 6 (6w) weeks following probiotic or placebo supplementation.

P-values on the figure are p-values obtained by the pairwise t-test, adjusted for multiple testing by the Benjamini–Hochberg procedure.

Fig 6. Boxplot of community α diversity at day 0 (prior to supplementation) according to the Simpson index and categorized according to gestational age at birth.

Data are shown only for the weeks in which at least five infants were born.

Fig 7. PCA analysis of the preterm infant gut microbiome grouped according to the administration of Saccharomyces boulardii or placebo, categorized according to the time points 2 (2w) and 6 (6w) weeks following supplementation.

Only ten of the most abundant OTUs are shown. PC, principal component; var., variation; and S. Boulardii, Saccharomyces boulardii.

Fig 8. Boxplot of community α diversity, as expressed by the Simpson index, categorized according to the administration of the probiotic Saccharomyces boulardii (S. Boulardii) or placebo at 2 (2w) and 6 (6w) weeks following intervention.

P-values in Mann-Whitney U-test are shown for respective times.

Fig 9. PCA analysis of the infant gut microbiome, categorized according to time points and mode of delivery.

Only the ten most abundant OTUs are shown. 0, prior to supplementation; 2w and 6w, 2 weeks and 6 weeks following commencement of supplementation; PC, principal component; var., variation; VD, vaginal delivery; and CC, cesarean section.