Abstract:

Objective To investigate the dynamic changes and distribution of gut microbiota in extremely preterm infants within the first month after birth, and to provide a theoretical basis for early intervention with probiotics. Methods A prospective study was conducted. Extremely preterm infants admitted to our hospital from September 2022 to March 2023 were enrolled. Fecal samples were collected on postnatal days 7, 14, 21 and 28 for high-throughput 16S rRNA sequencing and bioinformatics analysis. Results A total of 35 extremely preterm infants (22 boys and 13 girls) with gestational age of (210±11) days and birth weight of (1419±339) g were enrolled, and 140 fecal samples were collected. At the phylum level, the dominant gut microbiota detected included Firmicutes and Proteobacteria, accounting for more than 80%. At the genus level, the dominant gut microbiota were mainly opportunistic bacteria, including Escherichia, Clostridium, Staphylococcus, Acinetobacter and Klebsiella, while the relative abundance of Bifidobacterium was less than 5%. The difference analysis of key flora showed that the difference in key flora at the phylum and genus level was mainly in Bacteroidetes (P=0.029), Cyanobacteria (P=0.011), Staphylococcus (P=0.010), and Roseobacter (P=0.040). The diversity analysis of gut microbiota showed that there was no significant difference in the Ace and Shannon values of Alpla diversity index at the four time points (P>0.05), while Chao value showed a gradual downward trend (P=0.001). The weighted-unifrac values of beta diversity analysis at the four time points were 0.412 (0.281-0.493), 0.498 (0.214-0.526), 0.428 (0.289-0.490) and 0.143 (0.077-0.423), respectively, and the difference was statistically significant (P<0.001). Conclusions From 7 to 28 days after birth, the dominant gut microbiota of extremely preterm infants gradually changes from Firmicutes to Proteobacteria, with opportunistic bacteria as the main flora. The number of Bifidobacterium colonized is small, and the diversity of gut microbiota shows a downward trend.

Key words: probiotics, extremely preterm infant, gut microbiota, 16S rRNA, high-throughput sequencing