Initial meconium microbiome in Chinese neonates delivered naturally or by cesarean section

Examination of the temporal and spatial dynamics of the gut microbiome in newborn piglets reveals distinct microbial communities in six intestinal segments

Intestinal microbiota plays a crucial role in immune development and disease progression in mammals from birth onwards. The gastrointestinal tract of newborn mammals is rapidly colonized by microbes with tremendous biomass and diversity. Understanding how this complex of segmental communities evolves in different gastrointestinal sites over time has great biological significance and medical implications. However, most previous reports examining intestinal microbiota have focused on fecal samples, a strategy that overlooks the spatial microbial dynamics in different intestinal segments. Using intestinal digesta from six intestinal segments (duodenum, jejunum, ileum, cecum, colon and rectum) of newborn piglets, we herein conducted a large-scale 16S rRNA gene sequencing-based study to characterize the segmental dynamics of porcine gut microbiota at eight postnatal intervals (days 1, 7, 14, 21, 28, 35, 120 and 180). A total of 4,465 OTUs were obtained and showed that the six intestinal segments could be divided into three parts; in the duodenum-jejunum section, the most abundant genera included Lactobacillus and Bacteroides; in the ileum, Fusobacterium and Escherichia; and in the cecum-rectum section, Prevotella. Although the microbial communities of the piglets were similar among the six intestinal segments on postnatal day 1, they evolved and quickly differentiated at later intervals. An examination of time-dependent alterations in the dominant microbes revealed that the microbiome in the large intestine was very different from and much more stable than that in the small intestine. The gut microbiota in newborn piglets exhibited apparent temporal and spatial variations in different intestinal segments. The database of gut microbes in piglets could be a referable resource for future studies on mammalian gut microbiome development in early host growth phases.

Characteristics of the Intestinal Microbiota in Very Low Birth Weight Infants With Extrauterine Growth Restriction

Objective: Very low birth weight (VLBW) infants, which experience significant postnatal growth restriction at the time of discharge, are at high risk of later growth failure and long-term consequences. This study aims to characterize the structure of intestinal microbiome community in VLBW infants with extrauterine growth restriction (EUGR). Methods: Twenty-three VLBW infants appropriate for gestational age (GA) hospitalized at the neonatal intensive care unit of the BaoAn Maternal and Child Care Hospital (Shenzhen, China) were enrolled in this study, which were divided into the growth restriction group (EUGR; n = 12) and the normal growth group (AGA; n = 11). Meconium and fecal samples at postnatal day 28 were collected respectively during hospitalization. Total bacterial DNA was extracted and sequenced using the Illumina MiSeq Sequencing System based on the V3-V4 hyper-variable regions of the 16S rRNA gene. Results: The intestinal bacterial communities of preterm infants were dominated by the phylum Proteobacteria. Compared with the AGA group, the relative abundances of the genera Aeromicrobium and Serratia in meconium samples significantly decreased, whereas genera Parabacteroides, Ruminococcus, Blautia, and Aeromonas were more prevalent in the EUGR group. On postnatal day 28, the relative abundances of the genera Parabacteroides, Bacteroides, Eubacterium, Granulicatella, and Salinivibrio were significantly different between the two groups, where genus Salinivibrio decreased significantly in the EUGR samples. Among them, genus Parabacteroides was more abundant on both postnatal day 1 and 28. Further KEGG prediction analysis showed that there were many differences in functional genes and pathways between the two groups on postnatal day 28, but not on day 1, the majority of which were related to energy metabolism. And no statistical differences were observed in the clinical characteristics of infants. Conclusions: Overall, these findings showed that a distinct gut microbiota profile presented in preterm infants with EUGR. The role of intestinal microbiome in the extrauterine growth of preterm infants during hospitalization should be further investigated.

Shaping Microbiota During the First 1000 Days of Life

The data obtained in prior studies suggest that early microbial exposition begins prior to conception and gestation. Given that the host-microbe interaction is shaped by the immune system response, it is important to understand the key immune system-microbiota relationship during the period from conception to the first years of life. The present work summarizes the available evidence concerning early microbiota exposure within the male and the female reproductive tracts at the point of conception and during gestation, focusing on the potential impact on infant development during the first 1000 days of life. Furthermore, we conclude that some dietary strategies including specific probiotics could become potentially valuable tools to modulate the gut microbiota during this early critical window of opportunity for targeted health outcomes throughout the entire lifespan.

The impacts of delivery mode on infant's oral microflora

This study investigated the effects of different delivery modes on oral microflora in healthy newborns immediately post-partum, and provided evidence for microbial colonization disruption induced by medical procedures. Eighteen infants delivered by cesarean section and 74 by vaginal delivery were included in the study. High-throughput sequencing of 16S bacterial rRNA was performed on oral samples collected immediately after birth. All data were analyzed using bioinformatics approaches. Our results indicated that different oral bacteria were found between infants delivered by cesarean section compared to vaginal delivery group. Lactobacillus, Prevotella and Gardnerella were the most abundant genera in the vaginal group, while Petrimonas, Bacteroides, Desulfovibrio, Pseudomonas, Staphylococcus, Tepidmicrobium, VadinCA02, and Bifidobacterium were dominant bacteria in the cesarean section (C-section) group. Furthermore, bacteria isolated from 27 vaginally-delivered infants were not clustered into the vaginal group. Most of them spent more than 24 hours in the delivery room and this led to repeated sterilization procedures. We hypothesized that repeated sterilization might have influenced oral microflora in those cases. To conclude, this study suggested that different modes of birth delivery affect oral microflora in healthy infants. In addition, attention shall be paid to the clinical practice of repeated sterilization of the vulva that possibly obstructs the colonization of vaginal bacterial.

A Critical Review of the Bacterial Baptism Hypothesis and the Impact of Cesarean Delivery on the Infant Microbiome

Numerous studies suggest that infants delivered by cesarean section are at a greater risk of non-communicable diseases than their vaginal counterparts. In particular, epidemiological studies have linked Cesarean delivery with increased rates of asthma, allergies, autoimmune disorders, and obesity. Mode of delivery has also been associated with differences in the infant microbiome. It has been suggested that these differences are attributable to the "bacterial baptism" of vaginal birth, which is bypassed in cesarean deliveries, and that the abnormal establishment of the early-life microbiome is the mediator of later-life adverse outcomes observed in cesarean delivered infants. This has led to the increasingly popular practice of "vaginal seeding": the iatrogenic transfer of vaginal microbiota to the neonate to promote establishment of a "normal" infant microbiome. In this review, we summarize and critically appraise the current evidence for a causal association between Cesarean delivery and neonatal dysbiosis. We suggest that, while Cesarean delivery is certainly associated with alterations in the infant microbiome, the lack of exposure to vaginal microbiota is unlikely to be a major contributing factor. Instead, it is likely that indication for Cesarean delivery, intrapartum antibiotic administration, absence of labor, differences in breastfeeding behaviors, maternal obesity, and gestational age are major drivers of the Cesarean delivery microbial phenotype. We, therefore, call into question the rationale for "vaginal seeding" and support calls for the halting of this practice until robust evidence of need, efficacy, and safety is available.