The Placental Microbiota Is Altered among Subjects with Gestational Diabetes Mellitus: A Pilot Study

Arthropods to Eutherians: A Historical and Contemporary Comparison of Sparse Prenatal Microbial Communities Among Animalia Species

Since the advent of next-generation sequencing, investigators worldwide have sought to discern whether a functional and biologically or clinically relevant prenatal microbiome exists. One line of research has led to the hypothesis that microbial DNA detected in utero/in ovo or prior to birth/hatching is a result of contamination and does not belong to viable and functional microbes. Many of these preliminary evaluations have been conducted in humans, mice, and nonhuman primates due to sample and specimen availability. However, a comprehensive review of the literature across animal species suggests organisms that maintain an obligate relationship with microbes may act as better models for interrogating the selective pressures placed on vertical microbial transfer over traditional laboratory species. To date, studies in humans and viviparous laboratory species have failed to illustrate the clear presence and transfer of functional microbes in utero. Until a ground truth regarding the status and relevance of prenatal microbes can be ascertained, it is salient to conduct parallel investigations into the prevalence of a functional prenatal microbiome across the developmental lifespan of multiple organisms in the kingdom Animalia. This comprehensive understanding is necessary not only to determine the role of vertically transmitted microbes and their products in early human health but also to understand their full One Health impact. This review is among the first to compile such comprehensive primary conclusions from the original investigator's conclusions, and hence collectively illustrates that prenatal microbial transfer is supported by experimental evidence arising from over a long and rigorous scientific history encompassing a breadth of species from kingdom Animalia.

The Association Between Microplastics and Microbiota in Placentas and Meconium: The First Evidence in Humans

Pregnancy and infancy are vulnerable times for detrimental environmental exposures. However, the exposure situation of microplastics (MPs) for mother-infant pairs and the adverse health effect of MPs are largely unknown. Therefore, we explored MP exposure in placentas and meconium samples, and the potential correlation of MP exposure with microbiota in placentas and meconium. A total of 18 mother-infant pairs were effectively recruited from Shanghai, China. The study required pregnant women to provide placentas and meconium samples. An Agilent 8700 laser infrared imaging spectrometer (LDIR) was applied to identify MPs. Microbiota detection was identified by 16S rRNA sequencing. Sixteen types of MPs were found in all matrices, and polyamide (PA) and polyurethane (PU) were the major types we identified. MPs detected in samples with a size of 20-50 μm were more than 76.46%. At the phylum level, both placenta and meconium microbiota were mainly composed of Proteobacteria, Bacteroidota, and Firmicutes. We also found some significant differences between placenta and meconium microbiota in β-diversity and gut composition. Additionally, we found polystyrene was inversely related with the Chao index of meconium microbiota. Polyethylene was consistently inversely correlated with several genera of placenta microbiota. The total MPs, PA, and PU consistently impacted several genera of meconium microbiota. In conclusion, MPs are ubiquitous in placentas and meconium samples, indicating the wide exposure of pregnant women and infants. Moreover, our findings may support a link between high concentration of MPs and microbiota genera in placentas and meconium. Additionally, there were several significant associations between the particle size of MPs in 50-100 μm and meconium microbiota.

Lachnospiraceae-derived butyrate mediates protection of high fermentable fiber against placental inflammation in gestational diabetes mellitus

Inflammation-associated insulin resistance is a key trigger of gestational diabetes mellitus (GDM), but the underlying mechanisms and effective interventions remain unclear. Here, we report the association of placental inflammation (tumor necrosis factor-α) and abnormal maternal glucose metabolism in patients with GDM, and a high fermentable dietary fiber (HFDF; konjac) could reduce GDM development through gut flora-short-chain fatty acid-placental inflammation axis in GDM mouse model. Mechanistically, HFDF increases abundances of Lachnospiraceae and butyrate, reduces placental-derived inflammation by enhancing gut barrier and inhibiting the transfer of bacterial-derived lipopolysaccharide, and ultimately resists high-fat diet-induced insulin resistance. Lachnospiraceae and butyrate have similar anti-GDM and anti-placental inflammation effects, and they can ameliorate placental function and pregnancy outcome effects probably by dampening placental immune dysfunction. These findings demonstrate the involvement of important placental inflammation-related mechanisms in the progression of GDM and the great potential of HFDFs to reduce susceptibility to GDM through gut-flora-placenta axis.

Prebiotics, Probiotics, and Synbiotics-A Research Hotspot for Pediatric Obesity

Childhood obesity is a major public health problem worldwide with an increasing prevalence, associated not only with metabolic syndrome, insulin resistance, hypertension, dyslipidemia, and non-alcoholic fatty liver disease (NAFLD), but also with psychosocial problems. Gut microbiota is a new factor in childhood obesity, which can modulate the blood lipopolysaccharide levels, the satiety, and fat distribution, and can ensure additional calories to the host. The aim of this review was to assess the differences and the impact of the gut microbial composition on several obesity-related complications such as metabolic syndrome, NAFLD, or insulin resistance. Early dysbiosis was proven to be associated with an increased predisposition to obesity. Depending on the predominant species, the gut microbiota might have either a positive or negative impact on the development of obesity. Prebiotics, probiotics, and synbiotics were suggested to have a positive effect on improving the gut microbiota and reducing cardio-metabolic risk factors. The results of clinical trials regarding probiotic, prebiotic, and synbiotic administration in children with metabolic syndrome, NAFLD, and insulin resistance are controversial. Some of them (Lactobacillus rhamnosus bv-77, Lactobacillus salivarius, and Bifidobacterium animalis) were proven to reduce the body mass index in obese children, and also improve the blood lipid content; others (Bifidobacterium bifidum, Bifidobacterium longum, Lactobacillus acidophilus, Lacticaseibacillus rhamnosus, Enterococcus faecium, and fructo-oligosaccharides) failed in proving any effect on lipid parameters and glucose metabolism. Further studies are necessary for understanding the mechanism of the gut microbiota in childhood obesity and for developing low-cost effective strategies for its management.

The maternal microbiome promotes placental development in mice

The maternal microbiome is an important regulator of gestational health, but how it affects the placenta as the interface between mother and fetus remains unexplored. Here, we show that the maternal gut microbiota supports placental development in mice. Depletion of the maternal gut microbiota restricts placental growth and impairs feto-placental vascularization. The maternal gut microbiota modulates metabolites in the maternal and fetal circulation. Short-chain fatty acids (SCFAs) stimulate cultured endothelial cell tube formation and prevent abnormalities in placental vascularization in microbiota-deficient mice. Furthermore, in a model of maternal malnutrition, gestational supplementation with SCFAs prevents placental growth restriction and vascular insufficiency. These findings highlight the importance of host-microbial symbioses during pregnancy and reveal that the maternal gut microbiome promotes placental growth and vascularization in mice.

Analysis of the microbiome in maternal, intrauterine and fetal environments based on 16S rRNA genes following different durations of membrane rupture

The incidence of chorioamnionitis and neonatal sepsis increases with the increasing time of rupture of membranes. Changes in the amount and categories of microbiomes in maternal and fetal environments after membrane rupture have yet to be discussed. In order to determine the microbiome diversity and signature in the maternal, intrauterine, and fetal environments of different durations following membrane rupture, we collected samples of fetal membrane, amniotic fluid, cord blood and maternal peripheral blood from singleton pregnant women and divided them into five groups according to the duration of membrane rupture. DNA was isolated from the samples, and the V3V4 region of bacterial 16S rRNA genes was sequenced. We found that the alpha diversity of the fetal membrane microbiome increased significantly 12 h after membrane rupture, while the beta diversity of the amniotic fluid microbiome increased 24 h after membrane rupture. In cord blood, the mean proportion of Methylobacterium and Halomonadaceae reached the highest 12 h after membrane rupture, and the mean proportion of Prevotella reached the highest 24 h after membrane rupture. The LEfSe algorithm showed that Ruminococcus, Paludibaculum, Lachnospiraceae, and Prevotella were detected earlier in cord blood or maternal blood and then detected in fetal membranes or amniotic fluid, which may suggest a reverse infection model. In conclusion, the microbes may invade the placenta 12 h after membrane rupture and invaded the amniotic cavity 24 h after membrane rupture. In addition to the common ascending pattern of infection, the hematogenous pathway of intrauterine infection should also be considered among people with rupture of membranes.

The Maternal Microbiome and Gestational Diabetes Mellitus: Cause and Effect

Gestational diabetes mellitus (GDM) is a growing public health concern that affects many pregnancies globally. The condition is associated with adverse maternal and neonatal outcomes including gestational hypertension, preeclampsia, placental abruption, preterm birth, stillbirth, and fetal growth restriction. In the long-term, mothers and children have an increased risk of developing metabolic diseases such as type 2 diabetes and cardiovascular disease. Accumulating evidence suggest that alterations in the maternal microbiome may play a role in the pathogenesis of GDM and adverse pregnancy outcomes. This review describes changes in the maternal microbiome during the physiological adaptations of pregnancy, GDM and adverse maternal and neonatal outcomes. Findings from this review highlight the importance of understanding the link between the maternal microbiome and GDM. Furthermore, new therapeutic approaches to prevent or better manage GDM are discussed. Further research and clinical trials are necessary to fully realize the therapeutic potential of the maternal microbiome and translate these findings into clinical practice.

Amplification of microbial DNA from bacterial extracellular vesicles from human placenta

Introduction

The placenta is essential for fetal growth and survival and maintaining a successful pregnancy. The sterility of the placenta has been challenged recently; however, the presence of a placental microbiome has been controversial. We tested the hypothesis that the bacterial extracellular vesicles (BEVs) from Gram-negative bacteria as an alternate source of microbial DNA, regardless of the existence of a microbial community in the placenta.

Methods

Placentae from the term, not in labor Cesareans deliveries, were used for this study, and placental specimens were sampled randomly from the fetal side. We developed a protocol for the isolation of BEVs from human tissues and this is the first study to isolate the BEVs from human tissue and characterize them.

Results

The median size of BEVs was 130-140 nm, and the mean concentration was 1.8-5.5 × 1010 BEVs/g of the wet placenta. BEVs are spherical and contain LPS and ompA. Western blots further confirmed ompA but not human EVs markers ALIX confirming the purity of preparations. Taxonomic abundance profiles showed BEV sequence reads above the levels of the negative controls (all reagent controls). In contrast, the sequence reads in the same placenta were substantially low, indicating nothing beyond contamination (low biomass). Alpha-diversity showed the number of detected genera was significantly higher in the BEVs than placenta, suggesting BEVs as a likely source of microbial DNA. Beta-diversity further showed significant overlap in the microbiome between BEV and the placenta, confirming that BEVs in the placenta are likely a source of microbial DNA in the placenta. Uptake studies localized BEVs in maternal (decidual) and placental cells (cytotrophoblast), confirming their ability to enter these cells. Lastly, BEVs significantly increased inflammatory cytokine production in THP-1 macrophages in a high-dose group but not in the placental or decidual cells.

Conclusion

We conclude that the BEVs are normal constituents during pregnancy and likely reach the placenta through hematogenous spread from maternal body sites that harbor microbiome. Their presence may result in a low-grade localized inflammation to prime an antigen response in the placenta; however, insufficient to cause a fetal inflammatory response and adverse pregnancy events. This study suggests that BEVs can confound placental microbiome studies, but their low biomass in the placenta is unlikely to have any immunologic impact.

Evaluating Current Molecular Techniques and Evidence in Assessing Microbiome in Placenta-Related Health and Disorders in Pregnancy

The microbiome is of great interest due to its potential influence on the occurrence and treatment of some human illnesses. It may be regarded as disruptions to the delicate equilibrium that humans ordinarily maintain with their microorganisms or the microbiota in their environment. The focus of this review is on the methodologies and current understanding of the functional microbiome in pregnancy outcomes. We present how novel techniques bring new insights to the contemporary field of maternal-fetal medicine with a critical analysis. The maternal microbiome in late pregnancy has been extensively studied, although data on maternal microbial changes during the first trimester are rare. Research has demonstrated that, in healthy pregnancies, the origin of the placental microbiota is oral (gut) rather than vaginal. Implantation, placental development, and maternal adaptation to pregnancy are complex processes in which fetal and maternal cells interact. Microbiome dysbiosis or microbial metabolites are rising as potential moderators of antenatal illnesses related to the placenta, such as fetal growth restriction, preeclampsia, and others, including gestational diabetes and preterm deliveries. However, because of the presence of antimicrobial components, it is likely that the bacteria identified in placental tissue are (fragments of) bacteria that have been destroyed by the placenta's immune cells. Using genomic techniques (metagenomics, metatranscriptomics, and metaproteomics), it may be possible to predict some properties of a microorganism's genome and the biochemical (epigenetic DNA modification) and physical components of the placenta as its environment. Despite the results described in this review, this subject needs further research on some major and crucial aspects. The phases of an in utero translocation of the maternal gut microbiota to the fetus should be explored. With a predictive knowledge of the impacts of the disturbance on microbial communities that influence human health and the environment, genomics may hold the answer to the development of novel therapies for the health of pregnant women.

Is there a placental microbiota? A critical review and re-analysis of published placental microbiota datasets

The existence of a placental microbiota is debated. The human placenta has historically been considered sterile and microbial colonization was associated with adverse pregnancy outcomes. Yet, recent DNA sequencing investigations reported a microbiota in typical human term placentas. However, this detected microbiota could represent background DNA or delivery-associated contamination. Using fifteen publicly available 16S rRNA gene datasets, existing data were uniformly re-analyzed with DADA2 to maximize comparability. While Amplicon Sequence Variants (ASVs) identified as Lactobacillus, a typical vaginal bacterium, were highly abundant and prevalent across studies, this prevalence disappeared after applying likely  DNA contaminant removal to placentas from term cesarean deliveries. A six-study sub-analysis targeting the 16S rRNA gene V4 hypervariable region demonstrated that bacterial profiles of placental samples and technical controls share principal bacterial ASVs and that placental samples clustered primarily by study origin and mode of delivery. Contemporary DNA-based evidence does not support the existence of a placental microbiota.ImportanceEarly-gestational microbial influences on human development are unclear. By applying DNA sequencing technologies to placental tissue, bacterial DNA signals were observed, leading some to conclude that a live bacterial placental microbiome exists in typical term pregnancy. However, the low-biomass nature of the proposed microbiome and high sensitivity of current DNA sequencing technologies indicate that the signal may alternatively derive from environmental or delivery-associated bacterial DNA contamination. Here we address these alternatives with a re-analysis of 16S rRNA gene sequencing data from 15 publicly available placental datasets. After identical DADA2 pipeline processing of the raw data, subanalyses were performed to control for mode of delivery and environmental DNA contamination. Both environment and mode of delivery profoundly influenced the bacterial DNA signal from term-delivered placentas. Aside from these contamination-associated signals, consistency was lacking across studies. Thus, placentas delivered at term are unlikely to be the original source of observed bacterial DNA signals.

The maternal microbiome promotes placental development in mice

The maternal microbiome is an important regulator of gestational health, but how it impacts the placenta as the interface between mother and fetus remains unexplored. Here we show that the maternal gut microbiota supports placental development in mice. Depletion of the maternal gut microbiota restricts placental growth and impairs feto-placental vascularization. The maternal gut microbiota modulates metabolites in the maternal and fetal circulation. Short-chain fatty acids (SCFAs) stimulate angiogenesis-related tube formation by endothelial cells and prevent abnormalities in placental vascularization in microbiota-deficient mice. Furthermore, in a model of maternal malnutrition, gestational supplementation with SCFAs prevents placental growth restriction and vascular insufficiency. These findings highlight the importance of host-microbial symbioses during pregnancy and reveal that the maternal gut microbiome promotes placental growth and vascularization in mice.

Ameliorative Effects of Bifidobacterium animalis subsp. lactis J-12 on Hyperglycemia in Pregnancy and Pregnancy Outcomes in a High-Fat-Diet/Streptozotocin-Induced Rat Model

Bifidobacterium, a common probiotic, is widely used in the food industry. Hyperglycemia in pregnancy has become a common disease that impairs the health of the mother and can lead to adverse pregnancy outcomes, such as preeclampsia, macrosomia, fetal hyperinsulinemia, and perinatal death. Currently, Bifidobacterium has been shown to have the potential to mitigate glycolipid derangements. Therefore, the use of Bifidobacterium-based probiotics to interfere with hyperglycemia in pregnancy may be a promising therapeutic option. We aimed to determine the potential effects of Bifidobacterium animalis subsp. lactis J-12 (J-12) in high-fat diet (HFD)/streptozotocin (STZ)-induced rats with hyperglycemia in pregnancy (HIP) and respective fetuses. We observed that J-12 or insulin alone failed to significantly improve the fasting blood glucose (FBG) level and oral glucose tolerance; however, combining J-12 and insulin significantly reduced the FBG level during late pregnancy. Moreover, J-12 significantly decreased triglycerides and total cholesterol, relieved insulin and leptin resistance, activated adiponectin, and restored the morphology of the maternal pancreas and hepatic tissue of HIP-induced rats. Notably, J-12 ingestion ameliorated fetal physiological parameters and skeletal abnormalities. HIP-induced cardiac, renal, and hepatic damage in fetuses was significantly alleviated in the J-12-alone intake group, and it downregulated hippocampal mRNA expression of insulin receptor (InsR) and insulin-like growth factor-1 receptor (IGF-1R) and upregulated AKT mRNA on postnatal day 0, indicating that J-12 improved fetal neurological health. Furthermore, placental tissue damage in rats with HIP appeared to be in remission in the J-12 group. Upon exploring specific placental microbiota, we observed that J-12 affected the abundance of nine genera, positively correlating with FBG and leptin in rats and hippocampal mRNA levels of InsR and IGF-1R mRNA in the fetus, while negatively correlating with adiponectin in rats and hippocampal levels of AKT in the fetus. These results suggest that J-12 may affect the development of the fetal central nervous system by mediating placental microbiota via the regulation of maternal-related indicators. J-12 is a promising strategy for improving HIP and pregnancy outcomes.

Changes in the Gut Microbiome and Pathologies in Pregnancy

Pregnancy is a special period in a woman's life when her organism undergoes multiple physiological changes so that the fetus has optimal conditions for growth and development. These include modifications in the composition of the microbiome that occur between the first and third trimesters of pregnancy. There is an increase in Akkermansia, Bifidobacterium, and Firmicutes, which have been associated with an increase in the need for energy storage. The growth in Proteobacteria and Actinobacteria levels has a protective effect on both the mother and the fetus via proinflammatory mechanisms. The aim of the study is to review the research on the relationship between the mother's intestinal microbiome and gestational pathologies. Changes in the maternal gut microbiome is probably one of the mechanisms that occurs in various pregnancy diseases such as preeclampsia, fetal growth restriction, gestational diabetes mellitus, excessive gestational weight gain, and premature birth. For this reason, it seems vital to pay attention to certain interventions that can benefit the affected patients both in the short term, by preventing complications during pregnancy, and in the long term, as one of the mechanisms occurring in various gestational diseases is dysbiosis of the maternal intestinal flora.

The Composition of Placental Microbiota and Its Association With Adverse Pregnancy Outcomes

To verify whether the placenta harbors bacteria, and to explore the composition of placental microbiota (if yes) and its association with adverse pregnancy outcomes. The placental microbiota was detected by 16S rRNA gene sequencing technology. In the process of detecting placental samples, exogenous marine bacterial DNA that does not exist in the human body was artificially added to obtain a visible 16S band. At the same time, the sterile samples, such as scissors, sheets, and cotton swabs, in delivery and operating rooms were collected as the environmental control samples. As a result, a total of 2,621,009 sequences were obtained from 71 samples, 88.9% of which came from artificially added exogenous bacterial DNA, suggesting that the placenta contained fewer bacteria. After removing the operational taxonomic units (OTUs) that coexisted in environmental controls, the placenta was annotated with 11 phyla, 22 classes, 43 orders, 79 families, and 157 genera. The β diversity analysis showed that there were significant differences in the placental microbiota between 10 women with gestational diabetes mellitus (GDM) (p AMOVA = 0.01) or 19 women with premature rupture of membranes (PROM) (p AMOVA = 0.004), and 21 women without adverse pregnancy outcomes, respectively. There were higher abundances of genera Bifidobacterium, Duncaniella, and Ruminococcus in the placenta samples of women with GDM. The genera of Bacteroides, Paraprevotella, and Ruminococcus were more enriched in the placental samples of women with PROM. The authors concluded that the placenta may harbor small amounts of microbiota, and significant differences in the dominant microbiota of the placenta were observed between those pregnant women with and without adverse pregnancy outcomes.

The Yin-Yang Concept of Pediatric Obesity and Gut Microbiota

The era of pediatric obesity is no longer a myth. Unfortunately, pediatric obesity has reached alarming incidence levels worldwide and the factors that contribute to its development have been intensely studied in multiple recent and emerging studies. Gut microbiota was recently included in the wide spectrum of factors implicated in the determination of obesity, but its role in pediatric obese patients is far from being fully understood. In terms of the infant gut microbiome, multiple factors have been demonstrated to shape its content, including maternal diet and health, type of delivery, feeding patterns, weaning and dietary habits. Nevertheless, the role of the intrauterine environment, such as the placental microbial community, cannot be completely excluded. Most studies have identified Firmicutes and Bacteroidetes as the most important players related to obesity risk in gut microbiota reflecting an increase of Firmicutes and a decrease in Bacteroidetes in the context of obesity; however, multiple inconsistencies between studies were recently reported, especially in pediatric populations, and there is a scarcity of studies performed in this age group.

Microbiome alterations in women with gestational diabetes mellitus and their offspring: A systematic review

AIMS

Gestational diabetes mellitus (GDM) is a metabolic disorder that might predispose pregnant women to develop type 2 Diabetes Mellitus or lead to severe adverse outcomes in their offspring. One of the factors that have been thought to be involved in the pathology behind this disorder is the microbiome. In this systematic review, we comprehensively review the documents regarding the microbiota alterations in different tracts of pregnant women with GDM and their offspring.

METHODS

A comprehensive search was conducted in major databases including MEDLINE (PubMed), Scopus, and Web of sciences up to August 2021. Data on the demographics, methodology, and microbiome alterations were extracted and classified according to the type of microbiome in pregnant women with GDM and their offspring. The quality of studies was assessed using the Newcastle-Ottawa Scale (NOS).

RESULTS

In 49 articles which were retrieved, the findings were variable on the level of changes in alpha and beta diversity, enrichment or depletion in phyla, genera, species and OTUs, in each microbiome type. Although there were some inconsistencies among the results, a pattern of significant alterations was seen in the gut, oral, vaginal microbiome of women with GDM and gut, oral, and placental microbiome of their offspring.

CONCLUSION

Even though the alteration of the microbiome of the different tracts was seen in the cases of GDM, the inconsistency among the studies prevents us from identifying unique pattern. However, the results seem promising and further studies that overcome the confounding factors related to the demographics and methodology are needed.

The evidence for placental microbiome and its composition in healthy pregnancies: A systematic review

OBJECTIVE

To assess the available scientific evidence regarding the placental microbial composition of a healthy pregnancy, the quality of this evidence, and the potential relation between placental and oral microbiome.

MATERIALS AND METHODS

Data sources: MEDLINE and EMBASE up to August 1, 2019.

STUDY ELIGIBILITY CRITERIA

Human subjects; healthy women; term deliveries; healthy normal birth weight; assessment of microorganisms (bacteria) in placental tissue; full research papers in English. The quality of the included studies was assessed by a modified Joanna Briggs Institute checklist for analytical cross-sectional studies.

RESULTS

57 studies passed the inclusion criteria. Of these, 33 had a high risk of quality bias (e.g., insufficient infection control, lack of negative controls, poor description of the healthy cases). The remaining 24 studies had a low (N = 12) to moderate (N = 12) risk of bias and were selected for in-depth analysis. Of these 24 studies, 22 reported microorganisms in placental tissues, where Lactobacillus (11 studies), Ureaplasma (7), Fusobacterium (7), Staphylococcus (7), Prevotella (6) and Streptococcus (6) were among the most frequently identified genera. Methylobacterium (4), Propionibacterium (3), Pseudomonas (3) and Escherichia (2), among others, although frequently reported in placental samples, were often reported as contaminants in studies that used negative controls.

CONCLUSIONS

The results support the existence of a low biomass placental microbiota in healthy pregnancies. Some of the microbial taxa found in the placenta might have an oral origin. The high risk of quality bias for the majority of the included studies indicates that the results of individual papers should be interpreted with caution.

Metagenomic profiling of placental tissue suggests DNA virus infection of the placenta is rare

It is widely recognized that pathogens can be transmitted across the placenta from mother to foetus. Recent re-evaluation of metagenomic studies indicates that the placenta has no unique microbiome of commensal bacteria. However, viral transmission across the placenta, including transmission of DNA viruses such as the human herpesviruses, is possible. A fuller understanding of which DNA virus sequence can be found in the placenta is required. We employed a metagenomic analysis to identify viral DNA sequences in placental metagenomes from full-term births (20 births), pre-term births (13 births), births from pregnancies associated with antenatal infections (12 births) or pre-term births with antenatal infections (three births). Our analysis found only a small number of DNA sequences corresponding to the genomes of human herpesviruses in four of the 48 metagenomes analysed. Therefore, our data suggest that DNA virus infection of the placenta is rare and support the concept that the placenta is largely free of pathogen infection.

The jury is still out on the existence of a placental microbiome

The human microbiome is crucial for regulating normal development, but the exact point when it is established remains unknown. A sterile placenta was traditionally considered a prerequisite for a healthy pregnancy, but studies have revealed that the placenta harbours microbial communities, even under normal conditions. However, reports have failed to provide evidence for the consistent presence of bacteria in the normal human placenta, challenging the in utero colonisation hypothesis. This mini review examines our understanding of the potential placental microbial colonisation in normal healthy pregnancies. This may impact the metabolic and immune functions of the growing foetus and have long-term consequences.

Oral microflora and pregnancy: a systematic review and meta-analysis

Understanding changes in oral flora during pregnancy, its association to maternal health, and its implications to birth outcomes is essential. We searched PubMed, Embase, Web of Science, and Cochrane Library in May 2020 (updated search in April and June 2021), and conducted a systematic review and meta-analyses to assess the followings: (1) oral microflora changes throughout pregnancy, (2) association between oral microorganisms during pregnancy and maternal oral/systemic conditions, and (3) implications of oral microorganisms during pregnancy on birth outcomes. From 3983 records, 78 studies were included for qualitative assessment, and 13 studies were included in meta-analysis. The oral microflora remains relatively stable during pregnancy; however, pregnancy was associated with distinct composition/abundance of oral microorganisms when compared to postpartum/non-pregnant status. Oral microflora during pregnancy appears to be influenced by oral and systemic conditions (e.g. gestational diabetes mellitus, pre-eclampsia, etc.). Prenatal dental care reduced the carriage of oral pathogens (e.g. Streptococcus mutans). The Porphyromonas gingivalis in subgingival plaque was more abundant in women with preterm birth. Given the results from meta-analyses were inconclusive since limited studies reported outcomes on the same measuring scale, more future studies are needed to elucidate the association between pregnancy oral microbiota and maternal oral/systemic health and birth outcomes.

Effects of Clostridium butyricum on growth performance, metabonomics and intestinal microbial differences of weaned piglets

Background

Weaning stress of piglets causes a huge economic loss to the pig industry. Balance and stability of the intestinal microenvironment is an effective way to reduce the occurance of stress during the weaning process. Clostridium butyricum, as a new microecological preparation, is resistant to high temperature, acid, bile salts and some antibiotics. The aim of present study is to investigate the effects of C. butyricum on the intestinal microbiota and their metabolites in weaned piglets.

Results

There was no statistical significance in the growth performance and the incidence of diarrhoea among the weaned piglets treated with C. butyricum during 0–21 days experimental period. Analysis of 16S rRNA gene sequencing results showed that the operational taxonomic units (OTUs), abundance-based coverage estimator (ACE) and Chao index of the CB group were found to be significantly increased compared with the NC group (P < 0.05). Bacteroidetes, Firmicutes and Tenericutes were the predominant bacterial phyla in the weaned piglets. A marked increase in the relative abundance of Megasphaera, Ruminococcaceae_NK4A214_group and Prevotellaceae_UCG-003, along with a decreased relative abundance of Ruminococcaceae_UCG-005 was observed in the CB group, when compared with the NC group (P < 0.05). With the addition of C. butyricum, a total of twenty-two significantly altered metabolites were obtained in the feces of piglets. The integrated pathway analysis by MetaboAnalyst indicated that arginine and proline metabolism; valine, leucine and isoleucine biosynthesis; and phenylalanine metabolism were the main three altered pathways, based on the topology. Furthermore, Spearman’s analysis revealed some altered gut microbiota genus such as Oscillospira, Ruminococcaceae_NK4A214_group, Megasphaera, Ruminococcaceae_UCG-005, Prevotella_2, Ruminococcaceae_UCG-002, Rikenellaceae_RC9_gut_group and Prevotellaceae_UCG-003 were associated with the alterations in the fecal metabolites (P < 0.05), indicating that C. butyricum presented a potential protective impact through gut microbiota. The intestinal metabolites changed by C. butyricum mainly involved the variation of citrulline, dicarboxylic acids, branched-chain amino acid and tryptophan metabolic pathways.

Conclusions

Overall, this study strengthens the idea that the dietary C. butyricum treatment can significantly alter the intestinal microbiota and metabolite profiles of the weaned piglets, and C. butyricum can offer potential benefits for the gut health.

Gut and Reproductive Tract Microbiota Adaptation during Pregnancy: New Insights for Pregnancy-Related Complications and Therapy

Pregnancy is characterized by maternal adaptations that are necessary to create a welcoming and hospitable environment for the fetus. Studies have highlighted how the microbiota modulates several networks in humans through complex molecular interactions and how dysbiosis (defined as quantitative and qualitative alterations of the microbiota communities) is related to human pathologies including gynecological diseases. This review analyzed how maternal uterine, vaginal, and gut microbiomes could impact on fetus health during the gestational period. We evaluated the role of a dysbiotic microbiota in preterm birth, chorioamnionitis, gestational diabetes mellitus and pre-eclampsia. For many years it has been hypothesized that newborns were sterile organisms but in the past few years this paradigm has been questioned through the demonstration of the presence of microbes in the placenta and meconium. In the future, we should go deeper into the concept of in utero colonization to better understand the role of microbiota through the phases of pregnancy. Numerous studies in the literature have already showed interesting results regarding the role of microbiota in pregnancy. This evidence gives us the hope that microbiota modulation could be a novel strategy to reduce the morbidity and mortality related to pregnancy complications in the future.

The oral microbiome of pregnant women facilitates gestational diabetes discrimination

The oral microbiota plays an important role in the development of various diseases, whereas its association with gestational diabetes mellitus (GDM) remains largely unclear. The aim of this study is to identify biomarkers from the oral microbiota of GDM patients by analyzing the microbiome of the saliva and dental plaque samples of 111 pregnant women. We find that the microbiota of both types of oral samples in GDM patients exhibits differences and significantly varies from that of patients with periodontitis or dental caries. Using bacterial biomarkers from the oral microbiota, GDM classification models based on support vector machine and random forest algorithms are constructed. The area under curve (AUC) value of the classification model constructed by combination of Lautropia and Neisseria in dental plaque and Streptococcus in saliva reaches 0.83, and the value achieves a maximum value of 0.89 by adding clinical features. These findings suggest that certain bacteria in either saliva or dental plaque can effectively distinguish women with GDM from healthy pregnant women, which provides evidence of oral microbiome as an informative source for developing noninvasive biomarkers of GDM.

Comparison of the Genital Microbiomes of Pregnant Aboriginal and Non-aboriginal Women

The genital microbiomes of women varies with racial background. Preterm birth and early-onset neonatal sepsis are two outcomes associated with genital infections during pregnancy. The rate of preterm birth in Aboriginal Australian mothers is high, as is the rate of early-onset sepsis in their infants. To date, no studies have been conducted to investigate genital microbiome taxa associated infection in this group of women. A prospective cohort study to characterize the vaginal and placental microbiomes of a group of these women from the Pilbara region was conducted at the Hedland Health Campus in Western Australia. Included in the study were gravidae Aboriginal (n = 23) and Non-aboriginal (n = 27) women in labor or for planned lower uterine segment Caesarean section. Employing sterile swabs, vaginal samples were obtained under sterile conditions immediately prior to vaginal delivery or planned Caesarean section; and placental samples were obtained under the same conditions during labor. Taxa present in the samples were identified by 16S rRNA amplicon sequencing (V4 region, 515F-806R). Taxon identity and abundance were established from Operational Taxonomic Unit (OTU) counts. Statistical analyses combining clinical metadata and sequencing results were employed to determine associations of taxa with racial background. The findings of this work served to enhance the current understanding of microbiota associated with health and disease in Aboriginal and Non-Aboriginal women. Differences were found between the vaginal and placental microbiomes of Aboriginal and Non-aboriginal women during pregnancy, as well as notable differences between the abundance of specific taxa in each racial group. The relative abundances of specific taxa were significantly different between participants with clinical signs of infection and those with healthy pregnancies. This work will contribute to understanding the causes of differences in rates of infection-driven preterm birth in various racial populations.

Evidence for contamination as the origin for bacteria found in human placenta rather than a microbiota

Until recently the in utero environment of pregnant women was considered sterile. Recent high-sensitivity molecular techniques and high-throughput sequencing lead to some evidence for a low-biomass microbiome associated with the healthy placenta. Other studies failed to reveal evidence for a consistent presence of bacteria using either culture or molecular based techniques. Comparing conflicting “placental microbiome” studies is complicated by the use of varied and inconsistent protocols. Given this situation, we undertook an evaluation of the in utero environment sterility using several controlled methods, in the same study, to evaluate the presence or absence of bacteria and to explain contradictions present in the literature. Healthy pregnant women (n = 38) were recruited in three maternity wards. Placenta were collected after cesarean section with or without Alexis^® and vaginal delivery births. For this study we sampled fetal membranes, umbilical cord and chorionic villi. Bacterial presence was analyzed using bacterial culture and qPCR on 34 fetal membranes, umbilical cord and chorionic villi samples. Shotgun metagenomics was performed on seven chorionic villi samples. We showed that the isolation of meaningful quantities of viable bacteria or bacterial DNA was possible only outside the placenta (fetal membranes and umbilical cords) highlighting the importance of sampling methods in studying the in utero environment. Bacterial communities described by metagenomics analysis were similar in chorionic villi samples and in negative controls and were dependent on the database chosen for the analysis. We conclude that the placenta does not harbor a specific, consistent and functional microbiota.

Elimination of "kitome" and "splashome" contamination results in lack of detection of a unique placental microbiome

Background

A placental microbiome, which may be altered in gestational diabetes mellitus (GDM), has been described. However, publications raising doubts about the existence of a placental microbiome that is different than contaminants in DNA extraction kits and reagents (“kitomes”) have emerged. The aims of this study were to confirm the existence of a placental microbiome distinct from contaminants and determine if it is altered in GDM mothers.

Results

We first enrolled normal weight, obese and GDM mothers (N = 17) at term elective cesarean section delivery in a pilot case control study. Bacterial DNA was extracted from placental parenchyma, maternal and cord blood, maternal vaginal-rectal swabs, and positive and negative controls with the standard Qiagen/MoBio Power Soil kit. Placentas had significantly higher copies of bacterial 16S rRNA genes than negative controls, but the placental microbiome was similar in all three groups and could not be distinguished from contaminants in blank controls. To determine the source and composition of the putative placental bacterial community identified in the pilot study, we expanded the study to 10 subjects per group (N = 30) and increased the number and variety of negative controls (N = 53). We modified our protocol to use an ultraclean DNA extraction kit (Qiagen QIAamp UCP with Pathogen Lysis Tube S), which reduced the “kitome” contamination, but we were still unable to distinguish a placental microbiome from contaminants in negative controls. We noted microbial DNA from the high biomass vaginal-rectal swabs and positive controls in placental and negative control samples and determined that this resulted from close proximity well-to-well cross contamination or “splashome”. We eliminated this source of contamination by repeating the sequencing run with a minimum of four wells separating high biomass from low biomass samples. This reduced the reads of bacterial 16S rRNA genes in placental samples to insignificant numbers.

Conclusions

We identified the problem of well-to-well contamination (“splashome”) as an additional source of error in microbiome studies of low biomass samples and found a method of eliminating it. Once “kitome” and “splashome” contaminants were eliminated, we were unable to identify a unique placental microbiome.

Critical Relevance of Stochastic Effects on Low-Bacterial-Biomass 16S rRNA Gene Analysis

DNA contamination from external sources (reagents, environment, operator, etc.) has long been assumed to be the main cause of spurious signals that appear under low-bacterial-biomass conditions. Here, we demonstrate that contamination can be separated from another, random signal generated during low-biomass-sample sequencing. This stochastic noise is not reproduced between technical replicates; however, results for any one replicate taken alone could look like a microbial community different from the controls. Using this information, we investigated respiratory samples from healthy humans and determined the narrow range of bacterial biomass where samples transition from producing reproducible microbial sequences to ones dominated by noise. We present a rigorous approach to studies involving low-bacterial-biomass samples to detect this source of noise and provide a framework for deciding if a sample is likely to be dominated by noise. We anticipate that this work will facilitate increased reproducibility in the characterization of potentially important low-biomass communities.

The bacterial microbiome of human body sites, previously considered sterile, remains highly controversial because it can be challenging to isolate signal from noise when low-biomass samples are being analyzed. We tested the hypothesis that stochastic sequencing noise, separable from reagent contamination, is generated during sequencing on the Illumina MiSeq platform when DNA input is below a critical threshold. We first purified DNA from serial dilutions of Pseudomonas aeruginosa and from negative controls using three DNA purification kits, quantified input using droplet digital PCR, and then sequenced the 16S rRNA gene in four technical replicates. This process identified reproducible contaminant signal that was separable from an irreproducible stochastic noise, which occurred as bacterial biomass of samples decreased. This approach was then applied to authentic respiratory samples from healthy individuals (n = 22) that ranged from high to ultralow bacterial biomass. Using oral rinse, bronchoalveolar lavage (BAL) fluid, and exhaled breath condensate (EBC) samples and matched controls, we were able to demonstrate (i) that stochastic noise dominates sequencing in real-world low-bacterial-biomass samples that contain fewer than 10⁴ copies of the 16S rRNA gene per sample, (ii) that critical examination of the community composition of technical replicates can be used to separate signal from noise, and (iii) that EBC is an irreproducible sampling modality for sampling the microbiome of the lower airways. We anticipate that these results combined with suggested methods for identifying and dealing with noisy communities will facilitate increased reproducibility while simultaneously permitting characterization of potentially important low-biomass communities.

Gestational diabetes and the human salivary microbiota: a longitudinal study during pregnancy and postpartum

Background

An aberrant composition of the salivary microbiota has been found in individuals with type 2 diabetes, and in pregnant women salivary microbiota composition has been associated with preeclampsia and pre-term birth. Pregnant women, who develop gestational diabetes (GDM), have a high risk of developing type 2 diabetes after pregnancy. In the present study we assessed whether GDM is linked to variation in the oral microbial community by examining the diversity and composition of the salivary microbiota.

Method

In this observational study the salivary microbiota of pregnant women with GDM (n = 50) and normal glucose regulation (n = 160) in third trimester and 9 months postpartum was assessed by 16S rRNA gene amplicon sequencing of the V1-V3 region. GDM was diagnosed in accordance with the International Association of the Diabetes and Pregnancy Study Groups (IADPSG) criteria. Cross-sectional difference in alpha diversity was assessed using Student’s t-test and longitudinal changes were assessed by mixed linear regression. Cross-sectional and longitudinal difference in beta diversity was assessed by permutational multivariate analyses of variance. Differentially abundant genera and OTUs were identified by negative binomial regression.

Results

In the third trimester, two species-level operational taxonomic units (OTUs), while eight OTUs postpartum were differentially abundant in women with GDM compared with normoglycaemic women. OTU richness, Shannon diversity and Pielou evenness decreased from late pregnancy to 9 months after delivery regardless of glycaemic status.

Conclusion

GDM is associated with a minor aberration of the salivary microbiota during late pregnancy and postpartum. For unknown reasons richness of the salivary microbiota decreased from late pregnancy to postpartum, which might be explained by the physiological changes of the immune system during human pregnancy.

The Association Between Gestational Diabetes and Microbiota in Placenta and Cord Blood

Objective: Early life is a critical period for gut microbial development. It is still controversial whether there is placental microbiota during a healthy pregnancy. Gestational diabetes mellitus (GDM) is associated with increased risk of metabolic syndrome in the offspring, and the mechanisms are unclear. We sought to explore whether microbiota in placenta and cord blood may be altered in GDM. Methods: Placenta and cord blood samples were collected from eight GDM and seven euglycemic (control) term pregnancies in cesarean deliveries without evidence of clinical infections. The Illumina MiSeq Sequencing System was used to detect the microbiota based on the V3-V4 hypervariable regions of the 16S ribosomal RNA gene. Results: The microbiota were detectable in all placental samples. Comparing GDM vs. controls, there were more operational taxonomic units (OTUs) (mean ± SE = 373.63 ± 14.61 vs. 332.43 ± 9.92, P = 0.024) and higher ACE index (395.15 ± 10.56 vs. 356.27 ± 8.47, P = 0.029) and Chao index (397.67 ± 10.24 vs. 361.32 ± 8.87, P = 0.04). The placental microbiota was mainly composed of four phyla: Bacteroidetes, Firmicutes, Actinobacteria, and Proteobacteria at the phylum level and 10 dominant genera at the genus level in both GDM and controls. Despite the dominant similarity in microbiota composition, at the OTU level, the abundance of Ruminococcus, Coprococcus, Paraprevotella, and Lactobacillus were higher, whereas Veillonella was lower in the placentas of GDM vs. controls. The microbiota was detected in one of the 15 cord blood samples, and its components were similar as to the corresponding placental microbiota at both phylum and genus levels suggesting placental microbiota as the potential source. Conclusions: The most abundant phyla and genus of placental microbiota were similar in GDM and euglycemic pregnancies, but GDM was associated with higher diversity of placental microbiota. Further study is needed to confirm the existence of microbiota in cord blood in pregnancies without clinical infection.

Placental colonization with periodontal pathogens: the potential missing link

Observational studies demonstrate that women with severe periodontitis have a higher risk of adverse pregnancy outcomes like preterm birth and low birthweight. Standard treatment for periodontitis in the form of scaling and root planing during the second trimester failed to reduce the risk of preterm or low birthweight. It is premature to dismiss the association between periodontitis and adverse pregnancy outcomes because one explanation for the failure of scaling and root planing to reduce the risk of adverse pregnancy outcomes is that periodontal pathogens spread to the placental tissue prior to periodontal treatment. In the placenta, orally derived organisms could cause direct tissue damage or mediate a maternal immune response that impairs the growth of the developing fetus. Sequencing studies demonstrate the presence of organisms derived from the oral microbiome in the placenta, but DNA-based sequencing studies should not be the only technique to evaluate the placental microbiome because they may not detect important shifts in the metabolic capability of the microbiome. In humans, polymerase chain reaction and histology have detected periodontal pathogens in placental tissue in association with multiple adverse pregnancy outcomes. We conclude that both placental and oral microbiomes may play a role in periodontitis-associated adverse pregnancy outcomes. However, the measure to determine the association between periodontal pathogens in the placenta and adverse pregnancy outcomes should be the amount and prevalence, not the mere presence of such microorganisms. Placental colonization with periodontal pathogens thus potentially represents the missing link between periodontitis and adverse pregnancy outcomes.

A Narrative Review of Placental Contribution to Adverse Pregnancy Outcomes in Women With Polycystic Ovary Syndrome

CONTEXT

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy of reproductive-aged women. In pregnancy, women with PCOS experience increased risk of miscarriage, gestational diabetes, preeclampsia, and extremes of fetal birth weight, and their offspring are predisposed to reproductive and cardiometabolic dysfunction in adulthood. Pregnancy complications, adverse fetal outcomes, and developmental programming of long-term health risks are known to have placental origins. These findings highlight the plausibility of placental compromise in pregnancies of women with PCOS.

EVIDENCE SYNTHESIS

A comprehensive PubMed search was performed using terms "polycystic ovary syndrome," "placenta," "developmental programming," "hyperandrogenism," "androgen excess," "insulin resistance," "hyperinsulinemia," "pregnancy," and "pregnancy complications" in both human and animal experimental models.

CONCLUSIONS

There is limited human placental research specific to pregnancy of women with PCOS. Gestational androgen excess and insulin resistance are two clinical hallmarks of PCOS that may contribute to placental dysfunction and underlie the higher rates of maternal-fetal complications observed in pregnancies of women with PCOS. Additional research is needed to prevent adverse maternal and developmental outcomes in women with PCOS and their offspring.

Resveratrol treatment improves the altered metabolism and related dysbiosis of gut programed by prenatal high-fat diet and postnatal high-fat diet exposure

A maternal high-fat (HF) diet sensitizes offspring to the adverse effects of postnatal HF intake and can lead to metabolic dysregulation. Resveratrol, a natural polyphenolic compound found in grapes and red wine, could help to relieve metabolic syndrome dysregulation. Since the gut microbiota is known to be closely related to metabolic homeostasis, this study aimed to investigate the impact of a combination of maternal and postweaning HF diets on the gut microbiota and whether resveratrol could relieve the gut dysbiosis associated with metabolic dysregulation. Sprague-Dawley dams were sustained on either a chow or HF diet before mating, during pregnancy and during lactation. Their offspring were randomly fed chow or a HF diet after weaning. Four experimental groups were generated: CC (maternal/postnatal chow diet), HC (maternal HF/postnatal chow diet), CH (maternal chow/postnatal high-fat diet) and HH (maternal/postnatal HF diet). A fifth group consisted of HH with resveratrol treatment. We found that both maternal and postnatal HF exposure has a distinct effect on the gut microbiota metagenome of offspring. Maternal HF diet exposure decreased plasma acetate, propionate and butyrate level, while postnatal HF diet exposure decreased plasma acetate level in adult life. The metabolic dysregulation programed by the maternal and postnatal HF diets was related to the relevant gut microbiota. Resveratrol treatment ameliorated the altered plasma propionate level related to maternal HF and postnatal HF diet treatment. Resveratrol treatment also improved most of the altered metabolic dysregulation and related dysbiosis programmed by maternal and postnatal HF diet exposure.

Composition and maternal origin of the neonatal oral cavity microbiota

Background: The origin of the initial oral microbiota in neonates still remains poorly understood.

Objective: The aim of this study was to understand how the maternal microbiota contributes to the initial neonatal oral microbiota.

Design: Twelve mother-neonate pairs with samples from the maternal oral mucosa, uterine cervix and placenta and the neonatal oral cavity immediately after birth were studied. The microbiota composition and diversity were characterized by 16S rRNA gene sequencing (V3-V4 region). The microbiota analyses and comparisons were carried out with Calypso software version 8.1 and with SourceTracker 1.0.1.

Results: Samples from the neonatal oral cavity showed moderately high bacterial diversity and low richness. The neonatal oral cavity microbiota seems to share features mainly with the microbes detected in the placenta, followed by the cervical microbiota and the maternal oral microbiota. No statistically significant differences in diversity (Shannon index, p = 0.14), richness (Chao1, p = 0.53) or in microbial composition were observed according to delivery mode.

Conclusion: The neonatal oral cavity microbiota is not significantly modulated by the birth canal or maternal oral microbiota but displays clear associations with microbes in the placenta. These results suggest that the neonatal oral microbiota may have a prenatal origin.

A Novel Animal Model for Regional Microbial Dysbiosis of the Pioneer Microbial Community

Pioneer microbiota colonizing the newborn gastrointestinal tract has long-lasting effects on host health. Restoration of the gut microbial community, following dysbiosis during the neonatal period, may be one strategy to prevent undesirable health outcomes linked to an altered neonatal gut microbiome. Without appropriate animal models that recreate the prolonged human neonatal developmental period it is not possible to effectively analyze interventions designed to restore regional microbial populations. Our study used a lamb model in which intestinal segments were surgically isolated (blind-ended) in fetal lambs to create early microbial dysbiosis by delaying post-natal exposure to intestinal ingesta. Intestinal segments isolated in utero retained blood flow, innervation, and lymphatic drainage through the mesenteric attachment. Continuity of the fetal gastro-intestinal tract was re-established by side-to-side anastomosis of intestine proximal and distal to each isolated intestinal segment. Microbial restoration was then implemented in neonatal lambs by reconnecting a portion of the in utero isolated intestinal segments to adjacent intestinal tract 1 and 7 days after birth. Bacterial communities colonizing the adjacent intestine, in utero isolated intestinal segments, and reconnected intestinal segments were profiled using 16S amplicon sequencing on days 1, 7, and 56 of age. The in utero isolated intestinal segments were colonized 1 day after birth but the density of active bacteria was reduced and community composition altered when compared to adjacent intestine. Proteobacteria dominated the adjacent small intestine at early time points (day 1 and day 7) with a shift to primarily Firmicutes on day 56, consistent with establishment of an anaerobic bacterial community. In contrast, Proteobacteria persisted as the predominant community for 56 days in the in utero isolated intestinal segments. There was, however, almost full restoration of the microbial community composition in the in utero isolated intestinal segments following reconnection to the adjacent intestine. The density of beneficial bacteria, especially Bifidobacterium, remained significantly lower in the reconnected intestinal segments at 56 days when compared to adjacent intestine. Post-natal persistence of a stable pioneer community (Proteobacteria) in the in utero isolated intestinal segments provides a model system to study the temporal effects of regional microbial dysbiosis throughout a prolonged neonatal period.

Role for the mammalian female reproductive tract microbiome in pregnancy outcomes

Since the discovery of the microbiome in humans, it has been studied in many mammalian species. Different microbiological communities with variable richness and diversity have been found among these species in distinct areas of the reproductive tract. Human studies have shown that the composition of the microbiome is dependent on body site and several host-related factors. Furthermore, specific phyla have been identified among the different species and within distinct areas of the female reproductive tract, but a "core" microbiome of the female reproductive tract has not been defined in any species. Moreover, the function of the microbiome in the reproductive tract is not yet fully understood. However, it has been suggested that a change in diversity of the microbiome and the presence or absence of specific microbial species might be useful indicators of pregnancy outcomes. Increased comprehensive knowledge of the microbiological communities in the female reproductive tract is needed since adverse outcomes represent a significant problem to many species, including livestock, exotic or endangered species, and humans. To the authors' knowledge, a review combining current female reproductive tract microbiome data among different mammalian species has not been published yet. Herein is a comprehensive review of what is known in the field of the female reproductive microbiome and how it correlates with reproductive success or failure in mammals. Further studies may lead to optimization of therapies in the treatment of reproductive tract infections and pregnancy failure, and may create opportunities for novel approaches for improving reproductive efficiency in animals and people.

Factors influencing the gut microbiome in children: from infancy to childhood

The human microbiota plays a crucial role in educating the immune system and influencing host health right since birth. Various maternal factors along with the vertical microbial transfer from the mother, as well as the horizontal environmental transmission and internal factors relating to the infant, play a crucial role in modulating the gut microbiota. The early life microflora is highly unstable and undergoes dynamic changes during the first few years, converging towards a more stabilized adult microbiota by co-evolving with the host by the age of 3-4 years. Microbiota studies have underlined the role of dysbiosis in developing several metabolic disorders like obesity, diabetes and immune-related disorders like asthma, to name a few. Thus, understanding early life microbial composition and various factors affecting the microbial community will provide a platform for developing strategies/techniques to maintain host health by restoring gut microbial flora. This review focuses on the factors that affect the microbial composition of the foetus in utero, during birth, infancy through childhood.

The development and ecology of the Japanese macaque gut microbiome from weaning to early adolescence in association with diet

Previously we have shown that the Japanese macaque gut microbiome differs not by obesity per se, but rather in association with high-fat diet (HFD) feeding. This held true for both pregnant dams, as well as their 1-year-old offspring, even when weaned onto a control diet. Here we aimed to examine the stability of the gut microbiome over time and in response to maternal and postweaning HFD feeding from 6 months of age, and at 1 and 3 years of age. In both cross-sectional and longitudinal specimens, we performed analysis of the V4 hypervariable region of the 16S rRNA gene on anus swabs collected from pregnant dams and their juveniles at age 6 months to 3 years (n = 55). Extracted microbial DNA was subjected to 16S-amplicon-based metagenomic sequencing on the Illumina MiSeq platform. We initially identified 272 unique bacterial genera, and multidimensional scaling revealed samples to cluster by age and diet exposures. Dirichlet multinomial mixture modeling of microbiota abundances enabled identification of two predominant enterotypes to which samples sorted, characterized primarily by Treponema abundance, or lack thereof. Approximating the time of initial weaning (6 months), the Japanese macaque offspring microbiome underwent a significant state type transition which stabilized from 1 to 3 years of age. However, we also found the low abundance Treponema enterotype to be strongly associated with HFD exposure, be it during gestation/lactation or in the postweaning interval. Examination of taxonomic co-occurrences revealed samples within the low Treponema cluster were relatively permissive (allowing for increased interactions between microbiota) whereas samples within the high Treponema cluster were relatively exclusionary (suggesting decreased interactions amongst microbiota). Taken together, these findings suggest that Treponemes are keystone species in the developing gut microbiome of the gut, and susceptible to HFD feeding in their relative abundance.

The Initial Oral Microbiota of Neonates Among Subjects With Gestational Diabetes Mellitus

Objective: The objective was to investigate the potential effect of gestational diabetes mellitus on the initial neonatal oral microbiome community structure. Methods: Oral samples were collected from 20 full-term, vaginally delivered newborns with sterile swabs. Nine of them had mothers diagnosed with gestational diabetes mellitus (GDM group), while 11 had non-diabetic mothers (NDM group). The oral microbiota was analyzed using multi-barcode 16S rRNA sequencing on Illumina MiSeq system. Results: The results showed that the birth weight, gestational age and gestational weight gain were significantly higher in NDM group. There was a significant correlation between gestational age and birth weight. Neonatal oral microbiome was composed of five dominant phyla from Actinobacteria, Bacteroidetes, Firmicutes, Proteobacteria, and Tenericutes. Compared to NDM group, a higher alpha diversity and reduction of phylum Firmicutes were observed in GDM group. Genus Lactobacillus dominated in NDM group, while Alistipes, Streptococcus, and Faecalibacterium were overabundant in GDM group. Additionally, carbohydrate metabolism increased in NDM group, whereas amino acid metabolism, vitamin metabolism and lipopolysaccharide biosynthesis were more abundant in GDM group. Conclusions: This study showed a distinct oral microbiota profile in neonates born to mothers with GDM, which indicated that maternal diabetes status played an important role in neonatal initial oral microbiota.

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.

Offspring of mothers with hyperglycaemia in pregnancy: The short term and long-term impact. What is new?

The continuing rise in the global prevalence of diabetes and overweight or obesity has become a major burden for global health, as the pandemic is affecting both high and low-middle income countries (LMIC). At the same time, a similar pattern has been observed for all forms of hyperglycemia in pregnancy (HIP), diabetes during pregnancy and gestational diabetes. The offspring of mothers with HIP and/or overweight-obesity is receiving increasing attention as advances in early detection and treatment of HIP did not completely prevent macrosomia and its associated short-term perinatal disorders, whilst long term consequences are observed in the mother and in offspring as it reaches adulthood. This review discusses the current developments in the consequences of HIP in the offspring, with a particular focus on its long-term health at adulthood, and on intergenerational and transgenerational effects. HIP is emerging as one of the factors that can contribute, during the window of sensitivity to environmental cues constituted by the preconception, pregnancy, and early childhood, and as an amplifying factor linked to reproduction, to the current global epidemic of diabetes and non-communicable diseases (NCDs).

Changes in the gut microbiota composition during pregnancy in patients with gestational diabetes mellitus (GDM)

Gestational diabetes mellitus (GDM), a common pregnancy complication, is associated with an increased risk of maternal/perinatal outcomes. We performed a prospective observational explorative study in 41 GDM patients to evaluate their microbiota changes during pregnancy and the associations between the gut microbiota and variations in nutrient intakes, anthropometric and laboratory variables. GDM patients routinely received nutritional recommendations according to guidelines. The fecal microbiota (by 16S amplicon-based sequencing), was assessed at enrolment (24-28 weeks) and at 38 weeks of gestational age. At the study end, the microbiota α-diversity significantly increased (P < 0.001), with increase of Firmicutes and reduction of Bacteroidetes and Actinobacteria. Patients who were adherent to the dietary recommendations showed a better metabolic and inflammatory pattern at the study-end and a significant decrease in Bacteroides. In multiple regression models, Faecalibacterium was significantly associated with fasting glucose; Collinsella (directly) and Blautia (inversely) with insulin, and with Homeostasis-Model Assessment Insulin-Resistance, while Sutterella with C-reactive protein levels. Consistent with this latter association, the predicted metagenomes showed a correlation between those taxa and inferred KEGG genes associated with lipopolysaccharide biosynthesis. A higher bacterial richness and strong correlations between pro-inflammatory taxa and metabolic/inflammatory variables were detected in GDM patients across pregnancy. Collectively these findings suggest that the development of strategies to modulate the gut microbiota might be a potentially useful tool to impact on maternal metabolic health.

Changing environment of hyperglycemia in pregnancy: Gestational diabetes and diabetes mellitus in pregnancy

The diagnosis and treatment of gestational diabetes mellitus (GDM) have been in a state of flux since the World Health Organization accepted and endorsed the International Diabetes and Pregnancy Study Group's diagnostic pathway and criteria in 2013. These new diagnostic criteria identify an increasing number of women at risk of hyperglycemia in pregnancy (HGiP). Maternal hyperglycemia represents a significant risk to the mother and fetus, in both the short and long term. Controversially, metformin use for the treatment of GDM is increasing in Australia. This article identifies the multiple and varied presentations of HGiP, of which GDM is the most commonly encountered. The degree of maternal hyperglycemia experienced affects the outcomes for both the mother and neonate, and specific diagnosis determines the appropriate treatment for the pregnancy. Given the increasing incidence of women with dysglycemia and those developing HGiP, this is an important area for research and clinical attention for all health professionals.

HPV infection and bacterial microbiota in the placenta, uterine cervix and oral mucosa

We investigated the association between HPV infection and bacterial microbiota composition in the placenta, uterine cervix and mouth in thirty-nine women. HPV DNA genotyping of 24 types was conducted using Multimetrix®. Microbiota composition was characterized by 16S rRNA gene sequencing. HPV DNA was detected in 33% of placenta, 23% cervical and 33% oral samples. HPV16 was the most frequent type in all regions. HPV infection was associated with higher microbiota richness (p = 0.032) in the mouth but did not influence microbial diversity or richness in other samples. HPV infection was associated with higher abundance of Lactobacillaceae (p = 0.0036) and Ureaplasma (LDA score > 4.0, p < 0.05) in the placenta, Haemophilus (p = 0.00058) and Peptostreptococcus (p = 0.0069) genus in the cervix and Selenomonas spp. (p = 0.0032) in the mouth compared to HPV negative samples. These data suggest altered bacterial microbiota composition in HPV positive placenta, cervix and mouth. Whether the changes in bacterial microbiota predispose or result from HPV remains to be determined in future studies.

The developing gut microbiota and its consequences for health

The developmental origin of health and disease highlights the importance of the period of the first 1000 days (from the conception to the 2 years of life). The process of the gut microbiota establishment is included in this time window. Various perinatal determinants, such as cesarean section delivery, type of feeding, antibiotics treatment, gestational age or environment, can affect the pattern of bacterial colonization and result in dysbiosis. The alteration of the early bacterial gut pattern can persist over several months and may have long-lasting functional effects with an impact on disease risk later in life. As for example, early gut dysbiosis has been involved in allergic diseases and obesity occurrence. Besides, while it was thought that the fetus developed under sterile conditions, recent data suggested the presence of a microbiota in utero, particularly in the placenta. Even if the origin of this microbiota and its eventual transfer to the infant are nowadays unknown, this placental microbiota could trigger immune responses in the fetus and would program the infant's immune development during fetal life, earlier than previously considered. Moreover, several studies demonstrated a link between the composition of placental microbiota and some pathological conditions of the pregnancy. All these data show the evidence of relationships between the neonatal gut establishment and future health outcomes. Hence, the use of pre- and/or probiotics to prevent or repair any early dysbiosis is increasingly attractive to avoid long-term health consequences.