目的 了解极早产儿生后1个月肠道菌群的动态变化及分布特征，为益生菌早期干预提供理论依据。方法 采取前瞻性研究方法，选取2022年9月至2023年3月本院收治的极早产儿为研究对象，收集生后第7、14、21、28天的粪便标本行16S rRNA高通量测序及生物信息分析。结果 共纳入极早产儿35例，男22例，女13例，出生胎龄210±11天，出生体重1 419±339g，收集粪便样本140份。在门水平上检测到的优势菌群包括厚壁菌门、变形菌门，占80%以上；属水平上检测到的优势菌群主要以条件致病菌为主，包括埃希菌属、梭菌属、葡萄球菌属、不动杆菌属和克雷伯杆菌属，而双歧杆菌属相对丰度均<5%。关键菌群差异分析发现，门及属水平的差异菌群主要为拟杆菌门（P=0.029）、蓝藻菌门（P=0.011）及葡萄球菌属（P=0.010）、罗氏菌属（P=0.040）。肠道菌群的多样性分析发现，四个时间点Alpla多样性指数Ace值及Shannon值比较差异无统计学差异（P>0.05），而Chao值呈逐渐下降趋势（P=0.001）；四个时间点的Beta多样性分析Weighted-unifrac值分别为0.412（0.281~0.493）、0.498（0.214~0.526）、0.428（0.289~0.490）、 0.143（0.077~0.423），差异有统计学意义（P<0.001）。结论 极早产儿生后7~28天肠道优势菌群从厚壁菌门逐渐转变为变形菌门，并以条件致病菌为主，而双歧杆菌属定植数量少，肠道菌群多样性呈下降趋势。

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.