The mortality rate of very preterm infants with birth weight <1500 g is as high as 15%. The survivors till discharge have a high incidence of significant morbidity, which includes necrotising enterocolitis (NEC), early-onset neonatal sepsis (EONS) and late-onset neonatal sepsis (LONS). More than 25% of preterm births are associated with microbial invasion of amniotic cavity. The preterm gut microbiome subsequently undergoes an early disruption before achieving bacterial maturation. It is postulated that bacterial gut colonisation at birth and postnatal intestinal dysbacteriosis precede the development of NEC and LONS in very preterm infants. In fact, bacterial colonization patterns in preterm infants greatly differ from term infants due to maternal chorioamnionitis, gestational age, delivery method, feeding type, antibiotic exposure and the environment factor in neonatal intensive care unit (NICU). In this regard, this review provides an overview on the gut bacteria in preterm neonates’ meconium and stool. More than 50% of preterm meconium contains bacteria and the proportion increases with lower gestational age. Researchers revealed that the gut bacterial diversity is reduced in preterm infants at risk for LONS and NEC. Nevertheless, the association between gut dysbacteriosis and NEC is inconclusive with regards to relative bacteria abundance and between-sample beta diversity indices. With most studies show a disruption of the Proteobacteria and Firmicutes preceding the NEC. Hence, this review sheds light on whether gut bacteria at birth either alone or in combination with postnatal gut dysbacteriosis are associated with mortality and the morbidity of LONS and NEC in very preterm infants.

中文翻译：

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探索肠道细菌在早产儿健康和疾病中的作用

出生体重<1500克的极早产儿死亡率高达15%。出院前的幸存者有很高的发病率，包括坏死性小肠结肠炎（NEC）、早发新生儿败血症（EONS）和晚发新生儿败血症（LONS）。超过25%的早产与微生物侵入羊膜腔有关。随后，早产儿肠道微生物组在细菌成熟之前经历了早期破坏。据推测，极早产儿出生时肠道细菌定植和出生后肠道菌群失调先于 NEC 和 LONS 的发生。事实上，由于母亲是否患有绒毛膜羊膜炎、胎龄、分娩方式、喂养方式、抗生素暴露以及新生儿重症监护病房（NICU）的环境因素，早产儿的细菌定植模式与足月儿有很大不同。在这方面，本综述概述了早产儿胎便和粪便中的肠道细菌。超过50%的早产胎便含有细菌，且该比例随着胎龄的降低而增加。研究人员发现，存在 LONS 和 NEC 风险的早产儿肠道细菌多样性降低。然而，就相对细菌丰度和样本间β多样性指数而言，肠道菌群失调与 NEC 之间的关联尚无定论。大多数研究表明，NEC 之前的变形菌门和厚壁菌门受到破坏。因此，本综述揭示了出生时肠道细菌单独或与出生后肠道菌群失调相结合是否与极早产儿的死亡率和 LONS 和 NEC 发病率相关。