Occurrence of bacteria and polymorphonuclear leukocytes in fetal compartments at parturition; relationships with foal and mare health in the peripartum period

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.

Microbial Profiling of Amniotic Fluid, Umbilical Blood and Placenta of the Foaling Mare

The presence of a microbiome/microbiota in the placenta is hotly debated. In previous studies, the presence of bacteria in equine amniotic fluid and umbilical blood was independent of foal health. The objective of the present study was to determine if the same bacteria are present in the equine placenta as in amniotic fluid and umbilical blood. Samples were obtained from 24 parturient mares and foals. Placental bacterial DNA was extracted, and the microbiome was identified using 16S rRNA sequencing. All amniotic fluid samples contained some polymorphonucleocytes; bacteria were isolated from four samples. Aerobic or anaerobic growth was found in 18 and 3 umbilical blood samples, respectively. Serum amyloid A was <5 mg/L in all 24 samples, total WBC varied between 2900 and 10,700/µL, and fibrinogen varied between 0 and 5.16 g/L. In jugular blood, serum amyloid A was <5 mg/L in all 24 foals, total white blood count was 3200 to 8100/µL, and fibrinogen was 0.44 to 4.42 g/L. The diversity of bacterial microbiota was similar in all placental regions at the phylum level but differed at the genus level; the most abundant phyla were Proteobacteria (42-46.26%) and Actinobacteria (26.91-29.96%). In conclusion, bacteria were found in the fetal compartments and placenta of healthy equine pregnancies; however, we can neither prove nor disprove the hypothesis that the placenta has its own microbiome.

Partial convergence of the human vaginal and rectal maternal microbiota in late gestation and early post-partum

The human vaginal and fecal microbiota change during pregnancy. Because of the proximity of these perineal sites and the evolutionarily conserved maternal-to-neonatal transmission of the microbiota, we hypothesized that the microbiota of these two sites (rectal and vaginal) converge during the last gestational trimester as part of the preparation for parturition. To test this hypothesis, we analyzed 16S rRNA sequences from vaginal introitus and rectal samples in 41 women at gestational ages 6 and 8 months, and at 2 months post-partum. The results show that the human vaginal and rectal bacterial microbiota converged during the last gestational trimester and into the 2nd month after birth, with a significant decrease in Lactobacillus species in both sites, as alpha diversity progressively increased in the vagina and decreased in the rectum. The microbiota convergence of the maternal vaginal-anal sites perinatally might hold significance for the inter-generational transmission of the maternal microbiota.

Challenging the Hypothesis of in Utero Microbiota Acquisition in Healthy Canine and Feline Pregnancies at Term: Preliminary Data

At present, there are no data on the presence of bacteria in healthy canine and feline pregnancies at term. Here, we investigated the uterine microbiome in bitches (n = 5) and queens (n = 3) undergoing elective cesarean section in two facilities. Samples included swabs from the endometrium, amniotic fluid, and meconium, and environmental swabs of the surgical tray as controls. Culture and 16S rRNA gene sequencing were used to investigate the presence of bacteria. Culture was positive for 34.3% of samples (uterus n = 3, amniotic fluid n = 2, meconium n = 4, controls n = 0), mostly with low growth of common contaminant bacteria. With sequencing techniques, the bacterial abundance was significantly lower than in environmental controls (p < 0.05). Sequencing results showed a species-specific pattern, and significant differences between canine and feline bacterial populations were found at order, family, and genus level. No differences were found in alpha and beta diversities between feto-maternal tissues and controls (p > 0.05). Dominant phyla were Bacteroidetes, Firmicutes, and Proteobacteria in different proportions based on tissue and species. Culture and sequencing results suggest that the bacterial biomass is very low in healthy canine and feline pregnancies at term, that bacteria likely originate from contamination from the dam's skin, and that the presence of viable bacteria could not be confirmed most of the time.

Factors Affecting Gut Microbiota of Puppies from Birth to Weaning

The review described the most important factors affecting the development of the intestinal microbiota in puppies from birth to weaning. The health and well-being of the microbiome in puppies is influenced by the type of parturition, the maternal microbiota, and the diet of the mother, directly or indirectly. The isolation of bacteria in dogs from the placenta, fetal fluids, and fetuses suggests that colonization could occur before birth, although this is still a matter of debate. Accordingly, newborn puppies could harbor bacteria that could be of maternal origin and that could influence microbial colonization later in life. However, the long-term impacts on health and the clinical significance of this transfer is not yet clear and needs to be investigated. The same maternal bacteria were found in puppies that were born vaginally and in those delivered via cesarean section. Potentially, the relationship between the type of parturition and the colonization of the microbiome will influence the occurrence of diseases, since it can modulate the gut microbiome during early life. In addition, puppies' gut microbiota becomes progressively more similar to adult dogs at weaning, as a consequence of the transition from milk to solid food that works together with behavioral factors. A number of researches have investigated the effects of diet on the gut microbiota of dogs, revealing that dietary interference may affect the microbial composition and activity through the production of short-chain fatty acids and vitamins. These compounds play a fundamental role during the development of the fetus and the initial growth of the puppy. The composition of the diet fed during pregnancy to the bitches is also an important factor to consider for the health of newborns. As far as it is known, the effects of the type of parturition, the maternal microbiota, and the diet on the microbial colonization and the long-term health of the dogs deserve further studies. Definitely, longitudinal studies with a larger number of dogs will be required to assess a causal link between microbiome composition in puppies and diseases in adult dogs.

Morphological study of equine amniotic compartment

Exfoliative cytology of human amniotic fluid (AF) has been extensively studied since 1940s, but no data exist in equine species. The AF compartment represents the environment in which the foetus grows and matures, and its composition changes, reflecting foetal well-being and development. The aim of this study was to describe for the first time the morphology of equine AF cells and amniotic membrane (AM) with light microscopy (LM) and transmission electron microscopy (TEM). AF was collected at parturition within 5 min after the appearance of the AM with a 60 mL syringe from 34 mares and samples of AM were collected from a subset of 7 mares with normal pregnancy hospitalized for attended parturition. For LM observation, a sample of cytocentrifuged fresh AF was stained with May-Grünwald Giemsa and AM sections were stained with H-E. For TEM observation, AF and AM were fixed, embedded in epoxy resins, then sectioned and stained with uranyl acetate and lead citrate solutions. Nucleated and anucleated squamous cells with basophilic cytoplasm, intensely basophilic cornified cells, polymorphonuclear cells, and clusters of eosinophilic amorphous substance were observed. Cells presumably derived from tracheal epithelium and small round nucleated cells with eosinophilic cytoplasm presumably derived from amniotic or urinary epithelium were occasionally found. Lamellar body-like structures (LBs) were present in some epithelial cells. In AM, epithelial, basal and mesenchymal layers were clearly visible with both techniques as previously described. Epithelial cells had several cytoplasmic vacuolization and microvilli were present on apical surface. The connective tissue presented fibroblasts, mesenchymal and rare polymorphonuclear cells, surrounded by abundant extracellular matrix, with distribution of collagen fibres. This is the first report about equine amniotic compartment description by LM and TEM. As recently reported in human medicine, the AM could be a second potential source of pulmonary surfactant, given the finding of LBs inside the cells which could have the same function as in humans. Further studies in samples collected at different gestational ages could increase the knowledge of AF cells and their modification during pregnancy, as well as a better comprehension of the role of AM as a secondary source of pulmonary surfactant in the horse. The diagnostic evaluation of AF cellular composition in high-risk pregnancies may also be investigated.

Does Bacteria Colonization of Canine Newborns Start in the Uterus?

Simple Summary

A well-balanced microbial flora plays a fundamental role in puppies’ early development. Bacteria were thought to colonize newborns at birth, but some studies have challenged this hypothesis. A healthy fetus at term may already harbour bacteria and the uterus may also not be sterile. Time of initial microbiota development might be placed earlier in life. In this investigation we sampled uterus, amniotic fluid and meconium of healthy canine fetuses delivered through cesarean section (elective or emergency) and carried out bacteriological examinations. In contrast with the ‘sterile womb paradigm’, bacteria were isolated from all the sampled sites and materials, independently of the cesarean type. Further studies are necessary to confirm our results. We adopted traditional bacteria culture techniques, but molecular methods, which look for bacteria DNA, could also be performed to deepen the knowledge on this matter.

Abstract

The assumption that requires the uterus to be a sterile environment to sustain a successful pregnancy has been recently challenged in humans, and is still under debate. The aim of this study was to assess whether bacteria can be isolated from the pregnant uterus and from amniotic fluid and meconium of healthy canine fetuses at term, delivered through cesarean section. Fifteen dams of different breed, age and parity, undergoing either elective (n = 10) or emergency (n = 5) cesarean section after a healthy pregnancy, were included in the study. Swabs for bacterial culture were collected from the uterus, and from amniotic fluid and meconium. Bacteria were isolated from all the sampled sites and materials, irrespective of cesarean type. In most cases, different bacteria were isolated from the different sites. Acinetobacter spp., coagulase-negative Staphylococci and Bacillus spp. were frequently found while Pseudomonas aeruginosa, Micrococcus spp., Moraxella spp., Macrococcus spp., Glutamicibacter spp., Stenotrophomonas spp. and Psychrobacter spp. were only occasionally identified. Our data show that uterus and fetuses may not be sterile in healthy term canine pregnancies.

Do newborn puppies have their own microbiota at birth? Influence of type of birth on newborn puppy microbiota

With recent research in humans, a hypothesis known as the sterile womb paradigm has been challenged. The objectives of this study were to determine the presence of placental and fetal microbiomes in dogs, the effect of different types of parturition on the fetal microbiome, and the effect that the fetal microbiome has on early puppy development. A total of 96 newborn puppies from 17 dams were included in the study. Puppies were divided into two groups depending on the type of parturition (vaginal birth (VB) or cesarean section (CS)). Immediately after birth, swabs of the placenta and meconium were taken. Swabs of the oral and vaginal mucosa of the dam were taken in the second half of the pregnancy and just before parturition. All samples were analyzed with a classical bacteriological examination, and bacterial colonies were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The weight gain of each puppy was tracked daily in the first 7 days postpartum. Bacteria from several different genera were isolated from 86.5% of meconium samples and 57% of placenta samples. While the meconium microbiota resembled bacteria from the maternal vagina in VB puppies, the meconium microbiota of puppies born by CS indicated a relative resemblance to maternal oral and vaginal microbiota. A statistically significant difference in the relative growth rate between puppies born by VB and CS was found (p < 0.05), with puppies born by VB gaining weight faster compared to the CS group. This difference was even more noticeable when VB puppies were compared to puppies born by elective CS. Puppies born without a detectable meconium or placental microbiota showed a slower growth rate than those with a meconium microbiota, regardless of the type of parturition (p < 0.05). The findings of this study provide new information about the placental microbiome in healthy pregnant dams and suggest intrauterine colonization of the fetus in dogs. It seems that the type of delivery and bacterial colonization might be an important consideration for the weight gain in puppies in the first few days of life.

Development of Swine's Digestive Tract Microbiota and Its Relation to Production Indices-A Review

Simple Summary

Proper cooperation between digestive system microbiota and the host is an important issue in maintaining proper health condition, and—in the case of farm animals—production indices. In the case of pigs, microbiota significantly affect production parameters such as meat quality, growth rate or improvement of immune response to infections. Understanding of pig digestive system microbiota and factors affecting this is an important issue. This may enable improvement of animal performance and stabilization of microbiota during their growth, reducing the risk of metabolic or systemic diseases.

Abstract

The development of research methods and tools related to microbiome investigation, as well as widened knowledge and awareness concerning the significance of microorganisms inhabiting mammalian organisms, has led to an increasing popularity of studies in this field. This review paper presents some issues related to the swine microbiome, its development starting from an early age of life and its status in adult animals, as well as factors affecting the microbiome in pigs. Attention is paid to the role of probiotics and prebiotics as alternatives to antibiotics in the context of post-weaning diarrhea treatment, and to the role of microorganisms inhabiting the digestive tract of pigs in performance indices formation. In veterinary and pork production practice, understanding of the swine microbiome and its relationships with the host organism may be useful in the prevention of some diseases and also in improvement of performance results of animals.

Prenatal establishment of the foal gut microbiota: a critique of the in utero colonisation hypothesis

Bacteria colonisation of the foal’s gastrointestinal tract (GIT) is a critical developmental stage, effecting subsequent immunological and health outcomes. It has long been thought that the equine fetus develops in a sterile intrauterine environment and GIT colonisation commences at birth. Research now suggests that bacteria isolated from amniotic fluid are the initial colonisers of the fetal GIT, and exposure to the dam’s microbiota and the external environment during birth provide supplementary colonisation. This in utero colonisation hypothesis has only recently been examined in the horse and microbiota were detected in the amniotic fluid and meconium of healthy equine pregnancies. This review highlights the possible colonisation routes of these bacteria into the fetal compartments and examines their likely origins from the existing maternal microbiome. However, the current data describing the amniotic microbiota of the horse are limited and there is a need for research to fill this gap. Understanding the significance of intrauterine microbes for foal GIT colonisation may provide strategies to improve neonatal health.

The composition of the perinatal intestinal microbiota in cattle

Recent research suggests that the microbial colonization of the mammalian intestine may begin before birth, but the observations are controversial due to challenges in the reliable sampling and analysis of low-abundance microbiota. We studied the perinatal microbiota of calves by sampling them immediately at birth and during the first postnatal week. The large size of the bovine newborns allows sampling directly from rectum using contamination-shielded swabs. Our 16S rDNA data, purged of potential contaminant sequences shared with negative controls, indicates the existence of a diverse low-abundance microbiota in the newborn rectal meconium and mucosa. The newborn rectal microbiota was composed of Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. The microbial profile resembled dam oral rather than fecal or vaginal vestibular microbiota, but included typical intestinal taxa. During the first postnatal day, the rectum was invaded by Escherichia/Shigella and Clostridia, and the diversity collapsed. By 7 days, diversity was again increasing. In terms of relative abundance, Proteobacteria were replaced by Firmicutes, Bacteroidetes and Actinobacteria, including Faecalibacterium, Bacteroides, Lactobacillus, Butyricicoccus and Bifidobacterium. Our observations suggest that mammals are seeded before birth with a diverse microbiota, but the microbiota changes rapidly in the early postnatal life.