Effects of Probiotics on Gut Microbiomes of Extremely Preterm Infants in the Neonatal Intensive Care Unit: A Prospective Cohort Study

Abstract

Background: Probiotics have been previously reported to reduce the incidence of necrotizing enterocolitis (NEC) in extremely preterm infants, but the mechanisms by which the probiotics work remain unknown. We aimed to investigate the effects of probiotics on the gut microbiota of extremely preterm infants. Methods: A prospective cohort study was conducted on 120 extremely preterm neonates (gestational age ≤ 28 weeks) between August 2019 and December 2021. All neonates were divided into the study (receiving probiotics) and the control (no probiotics) groups. Multivariate logistic regression analysis was performed to investigate the significantly different compositions of gut microbiota between these two groups. The effects of probiotics on the occurrence of NEC and late-onset sepsis were also investigated. Results: An increased abundance of Lactobacillus was noted in neonates who received the probiotics (AOR 4.33; 95% CI, 1.89-9.96, p = 0.009) when compared with the control group. Subjects in the probiotic group had significantly fewer days of total parenteral nutrition (median [interquartile range, IQR]) 29.0 (26.8-35.0) versus 35.5 (27.8-45.0), p = 0.004) than those in the control group. The probiotic group had a significantly lower rate of late-onset sepsis than the control group (47.1% versus 70.0%, p = 0.015), but the rate of NEC, duration of hospitalization and the final in-hospital mortality rates were comparable between these two groups. Conclusions: Probiotic supplementation of extremely preterm infants soon after the initiation of feeding increased the abundance of Lactobacillus. Probiotics may reduce the risk of late-onset sepsis, but further randomized controlled trials are warranted in the future.

Keywords: gut microbiome; necrotizing enterocolitis; neonatal immunity; neonates; probiotics.

Figure 1

The alpha diversity of the probiotic group was higher than that of the control group using the observed and Fisher diversity indices.

Figure 2

A PCoA plot evaluated by weighted UniFrac distances showed a significant differential distribution of gut microbiota between the probiotic and control groups (p = 0.005).

Figure 3

The percentage abundance of specific families (A) and genera (B) are compared between the probiotic and control infants. The 17 genera included had a mean abundance of at least 1% in one or both allocation groups and were included in the regression analysis. Bacteria less than 1% are grouped as “others”.

Figure 4

The LEfSe analysis showed that the microbiota richness was markedly increased in the probiotic group compared with the control group (A). The cladogram plot shows five taxonomic levels, with the phyla and genera levels plotted in the innermost and outermost rings, respectively. The phylum Actinobacteriota and class Actinobacteria were enriched and had the highest linear discriminant analysis (LDA) score in the probiotic group (B). The relative abundances of Bifidobacterium bifidum, Faecalibacterium prausnitzii, and Enterococcus faecium were significantly increased, but the abundance of Staphylococcus epidermidis was significantly lower in the probiotic group than in the control group (C).

Figure 4

The LEfSe analysis showed that the microbiota richness was markedly increased in the probiotic group compared with the control group (A). The cladogram plot shows five taxonomic levels, with the phyla and genera levels plotted in the innermost and outermost rings, respectively. The phylum Actinobacteriota and class Actinobacteria were enriched and had the highest linear discriminant analysis (LDA) score in the probiotic group (B). The relative abundances of Bifidobacterium bifidum, Faecalibacterium prausnitzii, and Enterococcus faecium were significantly increased, but the abundance of Staphylococcus epidermidis was significantly lower in the probiotic group than in the control group (C).

Figure 5

The PICRUSt2 was used to compare functional changes of bacterial communities between neonates with and without supplementation of probiotics. Comparison of the functional profiles between neonates in the probiotic and placebo groups showed that phosphatidylglycerol biosynthesis was slightly enriched in the probiotic group. The preQ0 biosynthesis that is associated with inflammation was also higher in the control group. Bonferroni-adjusted p-values < 0.05 indicate significance.