Investigating prenatal and perinatal factors on meconium microbiota: a systematic review and cohort study

An evaluation of in utero polycyclic aromatic hydrocarbon exposure on the neonatal meconium microbiome

INTRODUCTION

In utero exposure to environmental polycyclic aromatic hydrocarbon (PAH) is associated with neurodevelopmental impairments[1-8], prematurity[9-12] and low birthweight[9,13-15]. The gut microbiome serves as an intermediary between self and external environment; therefore, exploring the impact of PAH on microbiota may elucidate their role in disease. Here, we evaluated the effect of in utero PAH exposure on meconium microbiome.

METHODS

We evaluated 49 mother-child dyads within Fair Start Birth Cohort with full term delivery and adequate meconium sampling. Prenatal PAH was measured using personal active samplers worn for 48 h during third trimester. Post-processing, 35 samples with adequate biomass were evaluated for association between tertile of PAH exposure (high (H) vs low/medium (L/M)) and microbiome diversity.

RESULTS

No significant differences were observed in alpha diversity metrics, Chao1 and Shannon index, between exposure groups for total PAH. However, alpha diversity metrics were negatively associated with log benzo[a]anthracene (BaA) and log chrysene (Chry) with high exposure, but positively associated with log benzo[a]pyrene (BaP) with low/medium exposure. After adjustment for birthweight and sex, alpha diversity metrics were negatively associated with log BaA, BaP, Chry, Indeno (Zhang et al., 2021; Perera et al., 2018)pyrene (IcdP) and total PAH with high exposure. Conversely, with low/medium exposure, alpha diversity metrics positively correlated with log BaP and benzo[b]fluoranthane (BbF). No significant difference in beta diversity was observed across groups using UniFrac, weighted UniFrac, or Bray-Curtis methods. Differential expression analysis showed differentially abundant taxa between exposure groups.

CONCLUSION

Bacterial taxa were detectable in 35/49 (71%) meconium samples. Altered alpha diversity metrics and differentially abundant taxa between groups suggest in utero PAH exposure may impede early colonization. Sample size is limited, but these findings provide supporting evidence for wider scale research. Research on long-term impact of prenatal PAH exposure on childhood health outcomes is ongoing. Differential effects of specific PAHs need further evaluation.

Comparison of Gut Microbiomes Between Neonates Born by Cesarean Section and Vaginal Delivery: Prospective Observational Study

Background: Balanced diversity and abundance of gut microbiome play important roles in human health, including neonatal health. Though not established, there is evidence that the delivery route could alter the diversity of neonatal gut microbiomes. Objective: The objective of the study was to investigate the differences in the gut microbiomes of neonates delivered via cesarean section compared to those born by vaginal delivery and to identify the predominant microbial taxa present in each group. Study Design: A prospective observational study of 281 healthy neonates born between February 2021 and April 2023 at Her Royal Highness Maha Chakri Sirindhorn Medical Center, Srinakharinwirot University, Thailand, was performed. The study population was divided into two groups: 139 neonates born via vaginal delivery and 141 neonates born via cesarean section. The microbiota composition of each neonate's fecal sample was identified by using 16S ribosomal ribonucleic acid metagenomic sequencing. Results: Neonates delivered vaginally exhibited a gut microbiome with higher abundance and diversity than those delivered by cesarean delivery. Bifidobacterium was the dominant genus in both groups. Bifidobacterium breve was the dominant species and was significantly higher in cesarean-delivered neonates compared to those delivered vaginally (24.0% and 9.2%, respectively) (p < 0.001). However, the taxonomy of only 89 (64.0%) and 44 (31.43%) fecal samples could be identified from the vaginal and cesarean delivery groups, respectively. Conclusion: Route of delivery is associated with neonatal gut microbiome abundance and diversity. Neonates delivered via vaginal delivery exhibited higher diversity but lower abundance of the dominant species in the gut microbiome. Trial Registration: Thai Clinical Trials Registry identifier: TCTR20221024003.

Dysbiosis of the initial stool microbiota increases the risk of developing necrotizing enterocolitis or feeding intolerance in newborns

Several perinatal factors influence the intestinal microbiome of newborns during the first days of life, whether during delivery or even in utero. These factors may increase the risk of developing necrotizing enterocolitis (NEC) by causing dysbiosis linked to a NEC-associated microbiota, which may also be associated with other gastrointestinal problems. The objective of our study was to evaluate the potential risks associated with microbial shifts in newborns with gastrointestinal symptoms and identify the intestinal microbiota of neonates at risk for NEC.During the study period, 310 preterm and term newborns' first passed meconium occurring within 72 h of birth were collected, and the microbiome was analyzed. We identified the risk factors in the NEC/FI group. Regarding microbiota, we compared the bacterial abundance between the NEC/FI group at the phylum and genus levels and explored the differences in the microbial composition of the 1st stool samples. A total of 14.8% (n = 46) of the infants were diagnosed with NEC or FI. In univariate analysis, the mean gestational age and birth weight were significantly lower in the NEC/FI group (p < 0.001). Prolonged rupture of membranes (PROM) > 18 h, chorioamnionitis, and histology were significantly higher in the NEC/FI group (p < 0.001). Multivariate analysis showed that gestational age (GA), prolonged membrane rupture (> 18 h), and early onset sepsis were consistently associated with an increased risk of NEC/FI. Infants diagnosed with NEC/FI exhibited a significantly lower abundance of Actinobacteria at the phylum level than the control group (p < 0.001). At the genus level, a significantly lower abundance of Streptococcus and Bifidobacterium which belong to the Actinobacteria phylum, was observed in the NEC/FI group (p < 0.001). Furthermore, the NEC/FI had significantly lower alpha diversities (Shannon Index,3.39 vs. 3.12; P = 0.044, respectively). Our study revealed that newborns with lower diversity and dysbiosis in their initial gut microbiota had an increased risk of developing NEC, with microbiota differences appearing to be associated with NEC/FI. Dysbiosis could potentially serve as a predictive marker for NEC- or GI-related symptoms.

Shaping Microbiota During the First 1000 Days of Life

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 human reproductive microbiota, and also, the microbial colonization during early life, focusing on the potential impact on infant development and health outcomes. Furthermore, we conclude that some dietary strategies including specific probiotics and other-biotics could become potentially valuable tools to modulate the maternal-neonatal microbiota during this early critical window of opportunity for targeted health outcomes throughout the entire lifespan.

Winds of change a tale of: asthma and microbiome

The role of the microbiome in asthma is highlighted, considering its influence on immune responses and its connection to alterations in asthmatic patients. In this context, we review the variables influencing asthma phenotypes from a microbiome perspective and provide insights into the microbiome's role in asthma pathogenesis. Previous cohort studies in patients with asthma have shown that the presence of genera such as Bifidobacterium, Lactobacillus, Faecalibacterium, and Bacteroides in the gut microbiome has been associated with protection against the disease. While, the presence of other genera such as Haemophilus, Streptococcus, Staphylococcus, and Moraxella in the respiratory microbiome has been implicated in asthma pathogenesis, indicating a potential link between microbial dysbiosis and the development of asthma. Furthermore, respiratory infections have been demonstrated to impact the composition of the upper respiratory tract microbiota, increasing susceptibility to bacterial diseases and potentially triggering asthma exacerbations. By understanding the interplay between the microbiome and asthma, valuable insights into disease mechanisms can be gained, potentially leading to the development of novel therapeutic approaches.

From Mother to Infant, from Placenta to Gut: Understanding Varied Microbiome Profiles in Neonates

The field of human microbiome and gut microbial diversity research has witnessed a profound transformation, driven by advances in omics technologies. These advancements have unveiled essential connections between microbiome alterations and severe conditions, prompting the development of new frameworks through epidemiological studies. Traditionally, it was believed that each individual harbored unique microbial communities acquired early in life, evolving over the course of their lifetime, with little acknowledgment of any prenatal microbial development, but recent research challenges this belief. The neonatal microbiome's onset, influenced by factors like delivery mode and maternal health, remains a subject of intense debate, hinting at potential intrauterine microbial processes. In-depth research reveals associations between microbiome profiles and specific health outcomes, ranging from obesity to neurodevelopmental disorders. Understanding these diverse microbiome profiles is essential for unraveling the intricate relationships between the microbiome and health outcomes.