Survival, distribution, and translocation of Enterococcus faecalis and implications for pregnant mice

Moderately pathogenic maternal influenza A virus infection disrupts placental integrity but spares the fetal brain

Maternal infection during pregnancy is a known risk factor for offspring mental health disorders. Animal models of maternal immune activation (MIA) have implicated specific cellular and molecular etiologies of psychiatric illness, but most rely on pathogen mimetics. Here, we developed a mouse model of live H3N2 influenza A virus (IAV) infection during pregnancy that induces a robust inflammatory response but is sublethal to both dams and offspring. We observed classic indicators of lung inflammation and severely diminished weight gain in IAV-infected dams. This was accompanied by immune cell infiltration in the placenta and partial breakdown of placental integrity. However, indications of fetal neuroinflammation were absent. Further hallmarks of mimetic-induced MIA, including enhanced circulating maternal IL-17A, were also absent. Respiratory IAV infection did result in an upregulation in intestinal expression of transcription factor RORγt, master regulator of a subset of T lymphocytes, TH17 cells, which are heavily implicated in MIA-induced etiologies. Nonetheless, subsequent augmentation in IL-17A production and concomitant overt intestinal injury was not evident. Our results suggest that mild or moderately pathogenic IAV infection during pregnancy does not inflame the developing fetal brain, and highlight the importance of live pathogen infection models for the study of MIA.

Extracellular superoxide produced by Enterococcus faecalis reduces endometrial receptivity via inflammatory injury

PROBLEM

Chronic endometritis (CE) can cause infertility. Enterococcus faecalis is an opportunistic pathogen that is often found in the endometrium of CE patients. However, the mechanisms by which E. faecalis affects endometrial health are still unclear. In this study, we investigated the mechanism how extracellular superoxide produced by E. faecalis affected the endometrial receptivity.

METHOD OF STUDY

Superoxide production was blocked by deleting menB gene in E. faecalis OG1RF. Endometrial epithelial cells were infected by superoxide-producing E. faecalis OG1RF and superoxide-deficient strain WY84. Inflammatory cytokines, apoptosis, and biomarkers for the endometrial receptivity were analyzed.

RESULTS

Infection of endometrial epithelial cells with superoxide-producing E. faecalis OG1RF induced expression of inflammatory cytokines, promoted apoptosis, and down-regulated expression of receptivity biomarkers compared to uninfected control. In contrast, superoxide-deficient E. faecalis WY84 had little effect on inflammatory cytokine production, apoptosis, and endometrial receptivity biomarkers.

CONCLUSIONS

Extracellular superoxide produced by E. faecalis is an important virulence factor for E. faecalis-induced endometritis leading to reduced receptivity of endometrial epithelial cells.

Protection of surface layer protein from Enterococcus faecium WEFA23 against Listeria monocytogenes CMCC54007 infection by modulating intestinal permeability and immunity

Enterococcus faecium WEFA23 was previously found effectively against adherence and colonization of Listeria monocytogenes CMCC54007, which might be closely related to its surface layer protein (SLP). In this study, the protective of SLP of E. faecium WEFA23 against infection of L. monocytogenes CMCC54007 was systemically investigated. In vitro assay showed that SLP actively inhibited L. monocytogenes internalization into Caco-2 cell line, with decreasing mRNA level of pro-inflammation cytokines and virulence factors and restoring destroyed intestinal barrier. In vivo assay through excluding SLP of E. faecium WEFA23 by 5 M LiCl represented that SLP increased body weight, reduced mortality and cell counts of L. monocytogenes CMCC54007 in tissues of mice. Further researches showed that SLP protected against L. monocytogenes CMCC54007 infection by modulation of intestinal permeability and immunity, namely, it decreased fluorescein isothiocyanate (FITC)-Dextran in serum, ameliorated destroyed colon structure, and increased number of goblet cells and protein level of TJ protein (Claudin-1, Occludin, and ZO-1) in colon. For immunity, SLP decreased number of CD4⁺ and CD8⁺ T cells in liver, mRNA level, and content of pro-inflammatory factors IL-6, IL-1β, IFN-γ ,TNF-α, and NO, and restored the structure of liver and spleen. Key Points•SLP of E. faecium inhibited L. monocytogenes internalization and colonization•SLP of E. faecium ameliorated host intestinal barrier dysfunction•SLP of E. faecium decreased pro-inflammatory cytokines and cells.

Unique maternal immune and functional microbial profiles during prenatal stress

Maternal stress during pregnancy is widespread and is associated with poor offspring outcomes, including long-term mental health issues. Prenatal stress-induced fetal neuroinflammation is thought to underlie aberrant neurodevelopment and to derive from a disruption in intrauterine immune homeostasis, though the exact origins are incompletely defined. We aimed to identify divergent immune and microbial metagenome profiles of stressed gestating mice that may trigger detrimental inflammatory signaling at the maternal-fetal interface. In response to stress, maternal glucocorticoid circuit activation corresponded with indicators of systemic immunosuppression. At the maternal-fetal interface, density of placental mononuclear leukocytes decreased with stress, yet maternal whole blood leukocyte analysis indicated monocytosis and classical M1 phenotypic shifts. Genome-resolved microbial metagenomic analyses revealed reductions in genes, microbial strains, and metabolic pathways in stressed dams that are primarily associated with pro-inflammatory function. In particular, disrupted Parasutterella excrementihominis appears to be integral to inflammatory and metabolic dysregulation during prenatal stress. Overall, these perturbations in maternal immunological and microbial regulation during pregnancy may displace immune equilibrium at the maternal-fetal interface. Notably, the absence of and reduction in overt maternal inflammation during stress indicates that the signaling patterns driving fetal outcomes in this context are more nuanced and complex than originally anticipated.

Probiotic Enterococcus faecalis Symbioflor 1 ameliorates pathobiont-induced miscarriage through bacterial antagonism and Th1-Th2 modulation in pregnant mice

The bacterium-bacterium interaction between pathogenic and probiotic Enterococcus as well as the bacterium-host interaction between Enterococcus and intestinal epithelium has drawn increasing attentions, but the influence of those interactions on host pregnancy remains largely unexplored. In the present study, we evaluated the effects of probiotic E. faecalis Symbioflor 1 or/and pathogenic E. faecalis OG1RF on the miscarriage of pregnant mice. Using in vitro assays of competition and exclusion and displacement, antagonistic property of E. faecalis Symbioflor 1 against E. faecalis OG1RF was observed, and the former inhibited the translocation of the later in vivo. The rate of miscarriage induced by E. faecalis OG1RF challenge was significantly reduced by 28% with E. faecalis Symbioflor 1 intervention; and the tissue integrity of ileum, colon, uterus, and placenta and placental blood cell density in pregnant mice were drastically improved by such probiotic intervention. Compared with the controls, probiotic intervention significantly upregulated the level of IL-10 and TGF-β, downregulated levels of IFN-γ, and increased progesterone level that reversed the trend of being Th1 predominance state reported for adverse pregnancy outcome at early pregnancy stage. In conclusion, E. faecalis Symbioflor 1 decreased the translocation of E. faecalis OG1RF, prevented pathogen-induced tissue damage, and changed Th1-Th2 homeostasis toward Th2 predominance during early pregnancy resulting in decreased miscarriage. KEY POINTS: •The mechanism of how probiotic E. faecalis Symbioflor 1 improves pregnancy of mice • Influence of interactions of pathogenic and probiotic Enterococcus on host pregnancy • E. faecalis Symbioflor 1 change Th1-Th2 homeostasis toward Th2 predominance.

Evaluation of gut bacterial community composition and antimicrobial resistome in pregnant and non-pregnant women from Saudi population

Background: Gut microbiota (GM) has recently been described as a functional reservoir of antimicrobial resistant genes (ARGs). However, the ARG-carrying bacterial species in the human gut has been poorly studied. This study, for the first time, is reporting bacterial communities' composition and antimicrobial resistome in the stool samples of pregnant and non-pregnant (NP) Saudi females. Methods: Gut bacterial community composition was analyzed by 16S amplicon sequencing and culturomics. High throughput MALDI-TOF technique was used for identification of the isolates from stool samples and evaluated for resistance against 13 antibiotics using the agar dilution method. Clinically important ARGs were PCR amplified from genomic DNA of the stool samples using gene-specific primers. Results: 16S amplicon sequencing revealed that GM of pregnant and NP women were predominantly comprised of phyla Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria. Bacterial diversity decreased in pregnant groups, whereas phylum Bacteroidetes declined significantly (p<0.05) in the first trimester. We noticed a relatively high abundance of butyrate-producing bacteria (eg, Faecalibacterium spp. and Eubacterium spp.) in the gut of pregnant women, whereas Prevotella copri was found at significantly (p<0.01) higher abundance in NP women. Moreover, about 14,694 isolates were identified and classified into 132 distinct species. The majority of the species belonged to phyla Firmicutes and Proteobacteria. About 8,125 isolates exhibited resistance against antibiotics. Out of 73 resistant-species, Enterococcus was the most diverse genus and Escherichia coli was the highly prevalent bacterium. The majority of the isolates were resistant to antibiotics; trimethoprim/sulfamethoxazole, cycloserine, and cefixime. ARGs encoding resistance against aminoglycoside, macrolide, quinolone, β-lactam, and tetracycline antibiotics were predominantly found in genomic DNA of the stool samples. Conclusion: We conclude that pregnancy-associated GM modulations may help to sustain a healthy pregnancy, but a higher proportion of antibiotic resistance could be deleterious for both maternal and fetal health.

Intrauterine Microbiota: Missing, or the Missing Link?

The intrauterine environment provides a key interface between the mother and the developing fetus during pregnancy, and is a target for investigating mechanisms of fetal programming. Studies have demonstrated an association between prenatal stress and neurodevelopmental disorders. The role of the intrauterine environment in mediating this effect is still being elucidated. In this review, we discuss emerging preclinical and clinical evidence suggesting the existence of microbial communities in utero. We also outline possible mechanisms of bacterial translocation to the intrauterine environment and immune responses to the presence of microbes or microbial components. Lastly, we overview the effects of intrauterine inflammation on neurodevelopment. We hypothesize that maternal gestational stress leads to disruptions in the maternal oral, gut, and vaginal microbiome that may lead to the translocation of bacteria to the intrauterine environment, eliciting an inflammatory response and resulting in deficits in neurodevelopment.

Transcriptomic Profiling of Human Placental Trophoblasts in Response to Infection with Enterococcus faecalis

Increasing evidence suggests that Enterococcus faecalis strains can pass through placental barriers and cause adverse outcomes during pregnancy. However, the underlying molecular mechanism of the interaction between E. faecalis and the host placental barrier has yet to be fully elucidated. In this study, we have used DNA microarray analysis to investigate the response of human placental trophoblast-like BeWo cells to infection with E. faecalis OG1RF. These results indicate that a total of 2191 genes in BeWo cells are differentially expressed in the presence of E. faecalis OG1RF, with 1357 genes being upregulated and 834 genes being downregulated. These differentially expressed genes (DEGs) are involved in apoptosis, stress and stimulus response, placental and embryonic development, immune response, and cell adhesion. Therefore, these results provide information on the molecular mechanisms that E. faecalis invasion can trigger to cause adverse pregnancy outcomes.