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During pregnancy, all major physiological systems undergo remarkable changes, driven largely by alterations in the maternal hormonal milieu. In healthy pregnancies, maternal cardiovascular and metabolic adaptation to pregnancy occurs to support fetal growth and maternal well-being. Impaired maternal adaptation to pregnancy is associated with a range of pregnancy complications, including gestational diabetes and preeclampsia. There is growing recognition of the importance of different maternal microbiota, including in the gut, vagina and oral cavity, in supporting normal maternal adaptations to pregnancy as well as evidence for microbial disturbances associating with pregnancy pathologies. Here, we aim to summarise emerging evidence demonstrating that differences in maternal microbiota associate with pregnancy outcomes and discuss potential therapeutic approaches under development that might restore an 'optimal' microbiome. In particular, we highlight recent work by ourselves and others exploring the role of the oral microbiome in pregnancy, given established links between poor oral health (e.g. periodontitis) and adverse pregnancy outcomes. Our research has focussed on specific nitrate-reducing oral bacteria which play a role in the generation of nitric oxide (NO) and other bioactive nitrogen oxides associated with cardiovascular health and maternal cardiovascular adaption to pregnancy. Ongoing research aims to define whether altered microbial profiles have clinical utility in the prediction of pregnancy pathologies, and whether interventions designed to optimise specific maternal microbiota could help prevent future complications. [ABSTRACT FROM AUTHOR]

The generation of nitrite by the oral microbiota is believed to contribute to healthy cardiovascular function, with oral nitrate reduction to nitrite associated with systemic blood pressure regulation. There is the potential to manipulate the composition or activities of the oral microbiota to a higher nitrate-reducing state through nitrate supplementation. The current study examined microbial community composition and enzymatic responses to nitrate supplementation in sessile oral microbiota grown in continuous culture. Nitrate reductase (NaR) activity and nitrite concentrations were not significantly different to tongue-derived inocula in model biofilms. These were generally dominated by Streptococcus spp., initially, and a single nitrate supplementation resulted in the increased relative abundance of the nitrate-reducing genera Veillonella, Neisseria, and Proteus spp. Nitrite concentrations increased concomitantly and continued to increase throughout oral microbiota development. Continuous nitrate supplementation, over a 7-day period, was similarly associated with an elevated abundance of nitratereducing taxa and increased nitrite concentration in the perfusate. In experiments in which the models were established in continuous low or high nitrate environments, there was an initial elevation in nitrate reductase, and nitrite concentrations reached a relatively constant concentration over time similar to the acute nitrate challenge with a similar expansion of Veillonella and Neisseria. In summary, we have investigated nitrate metabolism in continuous culture oral biofilms, showing that nitrate addition increases nitrate reductase activity and nitrite concentrations in oral microbiota with the expansion of putatively NaR-producing taxa. IMPORTANCE Clinical evidence suggests that blood pressure regulation can be promoted by nitrite generated through the reduction of supplemental dietary nitrate by the oral microbiota. We have utilized oral microbiota models to investigate the mechanisms responsible, demonstrating that nitrate addition increases nitrate reductase activity and nitrite concentrations in oral microbiota with the expansion of nitrate-reducing taxa. [ABSTRACT FROM AUTHOR]

Introduction: Chronic kidney disease (CKD) may affect the human microbiome via increased concentrations of uremic toxins such as urea and creatinine. Methods: We have profiled the oral microbiota in patients with CKD before and one week after kidney transplantation. Living kidney donors were also longitudinally tracked over a similar period, allowing direct comparison between a group undergoing transplant surgery alone (donors) (n=13) and a group additionally undergoing the introduction of immunosuppressive agents and the resolution of CKD (recipients) (n=45). Results: Transplantation was associated with a similar pattern of decreasing alpha diversity in the oral microbiome in recipients and donors via Kruskal-Wallis testing, within one week of transplantation. Amplicon sequence variants (ASVs) associated with Haemophilus parainfluenzae, Aggregatibacteria segnis, Peptostreptococcus and Actinobacillus were significantly decreased in recipients within a week of transplantation. Discussion: A reduction in ASVs in these genera could influence the risk of bacterial endocarditis, a rare but high-mortality kidney transplantation complication. A range of factors may drive the observed changes in oral microbiome including both factors associated with surgery itself and the decreases in salivary urea, administration of macrolide antibiotic immunosuppressants, and disruption to immune function that characterise kidney transplant. [ABSTRACT FROM AUTHOR]

The antibacterial effects of a polychromatic light device designed for intravenous application were assessed in vitro. Staphylococcus aureus, Klebsiella pneumoniae , or Escherichia coli were exposed to a 60-min sequential light cycle comprising 365, 530, and 630 nm wavelengths in circulated sheep blood. Bacteria were quantified by viable counting. The potential involvement of reactive oxygen species in the antibacterial effect was assessed using the antioxidant N-acetylcysteine-amide. A modified device was then used to determine the effects of the individual wavelengths. Exposure of blood to the standard wavelength sequence caused small (c. 0.5 Log 10 CFU) but statistically significant reductions in viable counts for all three bacteria, which were prevented by the addition of N-acetylcysteine-amide. Bacterial inactivation did not occur in blood-free medium, but supplementation with haem restored the moderate bactericidal effect. In single-wavelength experiments, bacterial inactivation occurred only with red (630 nm) light. Concentrations of reactive oxygen species were significantly higher under light stimulation than in unstimulated controls. In summary, exposure of bacteria within blood to a cycle of visible light wavelengths resulted in small but statistically significant bacterial inactivation apparently mediated by a 630 nm wavelength only, via reactive oxygen species possibly generated by excitation of haem groups. [ABSTRACT FROM AUTHOR]