Abstract
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.
Highlights
Prematurity is the leading cause of global under-5 deaths from the year 2015 [1]
This review aims to provide valuable insights into the gut bacteria in preterm neonates’ meconium and stool, gut bacteria in necrotising enterocolitis (NEC) and late-onset neonatal sepsis (LONS)
polymerase chain reaction (PCR)-based molecular studies identified that the predominant phyla in human gut microbiome Firmicutes, Bacteroidetes, Actinobacteria and Proteobacteria are present in the amniotic fluid during preterm labour [10,11,64]
Summary
Prematurity is the leading cause of global under-5 deaths from the year 2015 [1]. Preterm babies are born from 22 weeks to 36 weeks 6 days of gestational age. PCR-based molecular studies identified that the predominant phyla in human gut microbiome Firmicutes, Bacteroidetes, Actinobacteria and Proteobacteria are present in the amniotic fluid during preterm labour [10,11,64]. A recent in vivo study established a causal link between Ureaplasma species and adverse pregnancy and neonatal outcomes, demonstrating that the intra-amniotic inoculation of clinically isolated Ureaplasma species induced preterm birth and neonatal mortality by causing severe inflammatory response in several reproductive organs of pregnant mice [67] Taken together, these findings have indicated that the amniotic fluid from pregnant women who deliver prematurely, regardless of with intact or rupture membrane, is colonized with microorganisms
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