极低出生体重儿生后6个月内肠道菌群构成的动态变化

Composition of gut microbiota varies in very low birth weight infants within six months after birth

目的探讨极低出生体重儿生后6个月内肠道菌群定植特征及动态变化特点。方法选择2015年1月至12月收入新生儿重症监护病房的53例极低出生体重儿为研究对象，收集生后第1、7、14、28和180天（出院后）的粪便。采用Illumina MiSeq高通量测序技术对粪便样本DNA进行16S rRNA基因高通量测序及生物信息学分析，比较不同时间点肠道菌群相对丰度及多样性变化。采用Kruskal-Wallis秩和检验或Mann-Whitney U检验进行统计学分析。结果（1）门水平：5个时间点优势菌门均为变形菌门、厚壁菌门、拟杆菌门、放线菌门，其中变形菌门中位相对丰度第1天为0.598 5（0.122 3-0.942 6），1周后上升至0.893 2（0.478 1-0.987 0），14和28 d内维持在0.943 2-0.966 0，生后第180天回落至出生水平（P值均〈0.05）。放线菌门则出现相反的趋势，生后第180天相对丰度显著高于第1、7、14和28天（P值均〈0.05）。（2）属水平：克雷伯菌属出生第1天相对丰度较低为0.003 1（0.000 8-0.026 0），7-28 d间（0.326 5-0.368 2）显著高于出生时水平（P值均〈0.05），第180天回落至较低水平[0.008 1（0.000 5-0.067 1）]；埃希菌属丰度在生后1-14 d之间无显著差异，自28 d开始较前有显著上升（P值均〈0.05），180 d时显著高于住院期间其他各时间点（P值均〈0.05）。双歧杆菌出生时有一定丰度[0.000 5（0.000 1-0.004 2）]，但1-28 d一直维持在极低水平，至180 d达0.045 1（0.010 2-0.124 8），较前均有显著上升（P值均〈0.05）。（3）生后第14、28 d的Shannon指数显著低于生后第1天和第180天（1.81±0.71和1.89±0.56与2.33±1.29和2.26±0.55，P值均〈0.05）。结论与出生时相比，极低出生体重儿住院期间菌群多样性下降，变形菌门、克雷伯菌属成为优势菌；出院后菌群多样性恢复，双歧杆菌属、埃希菌属等常驻菌增加。NICU住院是极低出生体重儿肠道菌群多样性下降、微生态失衡的危险因素。

ObjectiveTo investigate the diversity of gut microbiota and its dynamic changes in very low birth weight infants （VLBWIs） during the first six months after birth.MethodsFrom January to December in 2015, 53 VLBWIs admitted to the Neonatal Intensive Care Unit （NICU） were recruited. Stool samples were collected from each subject on day 1, 7, 14 and 28 after birth as well as on day 180 during a follow-up visit. High-throughput 16S rRNA gene sequencing and bioinformatics analysis of bacterial DNA extracted from stool samples were performed using Illumina MiSeq platform double-end sequencing.Results（1） Phyla level： At all five time points, the dominant phyla were all Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria. The median relative abundance of Proteobacteria was 0.598 5 （0.122 3-0.942 6） on day 1, then rose to 0.893 2 （0.478 1-0.987 0） after one week, maintained at 0.943 2-0.966 0 within 28 days, and later dropped back to the same level as day 1 on day 180 （all P〈0.05）. In contrast, the median relative abundance of Actinobacteria on day 180 was significantly higher than that on days 1, 7, 14 and 28 （all P〈0.05）. （2） Genus level： The relative abundance of Klebsiella increased significantly between days 7 and 28 as compared with the lower level on day 1 [0.326 5-0.368 2 vs 0.003 1（0.000 8-0.026 0）, all P〈0.05], but significantly decreased to a lower level on day 180 [0.008 1 （0.000 5-0.067 1）]. There was no significant difference in the relative abundance of Escherichia within 14 days after birth. However, it significantly increased since day 28 （P〈0.05） and reached a peak on day 180 （P〈0.05）. Infants were born with a certain abundance of Bifidobacterium [0.000 5 （0.000 1-0.004 2）], which remained at a very low level for 28 days before reaching to a higher level of 0.045 1 （0.010 2-0.124 8） on day 180 （P〈0.05）. （3）The Shannon index on day 14 and 28 were lower than that of day 1 and day 180 （1.81±0.71, 1.89±1.270.56 vs 2.33±1.29, 2.2±0.5, all P〈0.05）, respectively.ConclusionsThe diversity of gut microbiota in VLBWIs decreases during NICU hospitalization as compared with that at birth when Proteobacteria and Klebsiella becoming the dominant bacteria. However, the diversity was regained after discharge with the increase of Bifidobacterium, Escherichia and other residential bacteria , which indicates that NICU hospitalization is a risk factor for dysbiosis in VLBWIs.