Changes in intestinal bacterial characteristics during hospitalization in the NICU in very low birth weight infants.

Background: The gut microbiota plays a crucial role in neonatal defense against pathogens, immune training, nutrient absorption, and postnatal disease development.

Methods: We prospectively collected fecal samples from 58 very low birth weight infants and 34 preterm infants with birth weights > 1500 g during their first two postnatal months. Using 16SrRNA sequencing, we characterize the compositional dynamics of gut microbiota in very low birth weight infants during early postnatal development, and evaluate potential associations with clinical factors.

Results: In the very low birth weight infants group (experimental group), a total of 45 bacterial phyla and 1,327 genera were identified. The top two dominant phyla were Proteobacteria (65.64%) and Firmicutes (29.64%), accounting for 95.28% collectively. Among the dominant phyla, the experimental group showed significantly higher levels of Bacteroidetes (P < 0.001) and Firmicutes (P = 0.018) compared to the control group, whereas Acidobacteria (P < 0.001), Proteobacteria (P < 0.001), Fusobacteria (P = 0.001), Chloroflexi (P = 0.018), and Patescibacteria (P = 0.006) were significantly lower. The top 10 dominant genera represented 91.9% of the total. At the genus level, the experimental group had significantly higher abundances of Klebsiella (P = 0.016), Streptococcus (P < 0.001), Corynebacterium_1 (P < 0.001), Clostridium_sensu_stricto_1 (P = 0.018), Clostridioides (P = 0.013), Staphylococcus (P < 0.001), and Lactobacillus (P = 0.001), while Escherichia_Shigella, Sphingomonas (P = 0.013), Veillonella (P = 0.037), Methylobacterium (P = 0.021), and Enterobacter (P = 0.029) were significantly lower compared to controls. Additionally, during the first 28 days after birth, the control group exhibited higher relative abundance of Bifidobacterium than the experimental group. Compared to preterm infants with birth weight > 1500 g, very low birth weight infants demonstrated more active intestinal metabolism. Within the very low birth weight infants, probiotic use, delivery mode, and premature rupture of membranes significantly influenced the relative abundances of Streptococcus, Clostridium_sensu_stricto_1, and Pseudomonas, respectively.

Conclusions: Very low birth weight infants exhibit distinct gut microbiota characteristics during their first two months of life. Factors including probiotic using, delivery mode, and premature rupture of membranes significantly influence specific bacterial populations. The gut microbiome represents a crucial influencing the health outcomes of very low birth weight infants.