The human female urogenital microbiome: complexity in normality

The endometrial microbiota and early pregnancy loss

The human endometrium is a dynamic entity that plays a pivotal role in mediating the complex interplay between the mother and developing embryo. Endometrial disruption can lead to pregnancy loss, impacting both maternal physical and psychological health. Recent research suggests that the endometrial microbiota may play a role in this, although the exact mechanisms are still being explored, aided by recent technological advancements and our growing understanding of host immune responses. Suboptimal or dysbiotic vaginal microbiota, characterized by increased microbial diversity and reduced Lactobacillus dominance, has been associated with various adverse reproductive events, including miscarriage. However, the mechanisms linking the lower reproductive tract microbiota with pregnancy loss remain unclear. Recent observational studies implicate a potential microbial continuum between the vaginal and endometrial niche in patients with pregnancy loss; however, transcervical sampling of the low biomass endometrium is highly prone to cross-contamination, which is often not controlled for. In this review, we explore emerging evidence supporting the theory that a dysbiotic endometrial microbiota may modulate key inflammatory pathways required for successful embryo implantation and pregnancy development. We also highlight that a greater understanding of the endometrial microbiota, its relationship with the local endometrial microenvironment, and potential interventions remain a focus for future research.

Safety, tolerability, and acceptability of Lactobacillus crispatus CTV-05 (LACTIN-V) in pregnant women at high-risk of preterm birth

The vaginal microbiota is a determinant for the risk of preterm birth (PTB). Dominance of the vaginal niche by Lactobacillus crispatus associates with term delivery. This is the first observational clinical study of live vaginal biotherapeutics (Lactobacillus crispatus CTV-05 (LACTIN-V)) in pregnant women at high-risk of PTB. The primary aim was to explore safety, tolerability and acceptability of LACTIN-V in pregnancy. Women were offered a course of LACTIN-V at 14 weeks gestation for five consecutive days followed by weekly administration for six weeks. Participants were followed up at 15, 18-, 20-, 28- and 36-weeks' gestation and at delivery for assessment of adverse events, compliance and tolerability. Participants completed a questionnaire to gauge experience and acceptability. In total, 73 women were recruited, of whom eight withdrew, leaving a final cohort size of 61. Self-reported compliance to the course was high (56/60, 93%). Solicited adverse events were reported in 13 women (19%) including changes in vaginal discharge, odour, colour or consistency of urine, itching and vaginal bleeding. One unsolicited adverse event was reported as haematuria at 38 weeks gestation, but was judged to be unrelated to LACTIN-V. No serious adverse events occurred. One mild adverse event led to study withdrawal. Thirty-one women completed an experience and acceptability questionnaire. Women found LACTIN-V easy and comfortable to use and the majority (30/31, 97%) would use LACTIN-V in future pregnancies. Eight women (8/31, 26%) found the schedule of use difficult to remember. The rate of PTB <34 weeks in this cohort was 3.3% compared to 7% in a historical cohort of 2,190 women at similar background PTB risk. With satisfactory uptake and good compliance, we demonstrate that LACTIN-V is safe and accepted in pregnancy, with high tolerability. Further studies are needed to assess colonisation of Lactobacillus crispatus CTV-05 and clinical efficacy.

N-glycosylation of cervicovaginal fluid reflects microbial community, immune activity, and pregnancy status

Human cervicovaginal fluid (CVF) is a complex, functionally important and glycan rich biological fluid, fundamental in mediating physiological events associated with reproductive health. Using a comprehensive glycomic strategy we reveal an extremely rich and complex N-glycome in CVF of pregnant and non-pregnant women, abundant in paucimannose and high mannose glycans, complex glycans with 2-4 N-Acetyllactosamine (LacNAc) antennae, and Poly-LacNAc glycans decorated with fucosylation and sialylation. N-glycosylation profiles were observed to differ in relation to pregnancy status, microbial composition, immune activation, and pregnancy outcome. Compared to CVF from women experiencing term birth, CVF from women who subsequently experienced preterm birth showed lower sialylation, which correlated to the presence of a diverse microbiome, and higher fucosylation, which correlated positively to pro-inflammatory cytokine concentration. This study is the first step towards better understanding the role of cervicovaginal glycans in reproductive health, their contribution to the mechanism of microbial driven preterm birth, and their potential for preventative therapy.

Influence of Maternal Microbiome and Inflammatory Response in Preterm Birth: Recent Aspects of the Prevention of Preterm Birth

Preterm birth (PTB) is a global health issue and one of the most challenging problems affecting 12.9 million births worldwide. PTB is a multi-etiological disease and remains incompletely understood. The major cause of PTB is infection or inflammation and disruption of the vaginal microbiome, which affects the maternal immunologic response leading to PTB. The vaginal microbiome composition changes by a shift in the community are typically dominated by Lactobacillus during pregnancy. There are complex interactions between the maternal microbiome in pregnancy and the development of PTB, therefore, researchers have struggled to connect the maternal microbiome with the dysregulation of the maternal immune response in cases of PTB. The host microbiome affects alterations of the microorganisms with external stimuli such as disease, nutrition, immunity, and behavior. In this review, we discuss the complex association between the maternal microbiome and the risk of PTB and also focus on recent aspects of the prevention of PTB.

Proteome-wide prediction of bacterial carbohydrate-binding proteins as a tool for understanding commensal and pathogen colonisation of the vaginal microbiome

Bacteria use carbohydrate-binding proteins (CBPs), such as lectins and carbohydrate-binding modules (CBMs), to anchor to specific sugars on host surfaces. CBPs in the gut microbiome are well studied, but their roles in the vagina microbiome and involvement in sexually transmitted infections, cervical cancer and preterm birth are largely unknown. We established a classification system for lectins and designed Hidden Markov Model (HMM) profiles for data mining of bacterial genomes, resulting in identification of >100,000 predicted bacterial lectins available at unilectin.eu/bacteria. Genome screening of 90 isolates from 21 vaginal bacterial species shows that those associated with infection and inflammation produce a larger CBPs repertoire, thus enabling them to potentially bind a wider array of glycans in the vagina. Both the number of predicted bacterial CBPs and their specificities correlated with pathogenicity. This study provides new insights into potential mechanisms of colonisation by commensals and potential pathogens of the reproductive tract that underpin health and disease states.

Monitoring of distribution of antibiotic-resistant strains of microorganisms in patients with dysbiosis of the urogenital tract

Currently, the problem of the development of resistance to drugs among microorganisms that colonize the urogenital system is becoming especially relevant due to broadly distributed dysbiotic conditions of the reproductive system of men and women. Therefore, there should be constant monitoring of the qualitative and quantitative composition of microbiota of the urogential tract and determination of the levels of antibiotic-resistance of strains of conditionally pathogenic microorganisms in the reproductive system of various layers of the population. We monitored 774,375 people of various age and sex – patients of the independent diagnostic laboratory INVITRO in the city Dnipro in 2017–2019. Among the examined people, 640,783 of the patients were diagnosed with the development of dysbiotic disorders, accounting for 82.7% of the total amount of the applications for medical help. According to the results of identification of the range of dysbiotic conditions of the urogenital system of patients of different ages and sexes, we determined the dominating role of facultative anaerobes in the development of dysbiotic impairments caused by colonizations by large numbers of conditionally-pathogenic microorganisms: in women, Gardnerella accounted for 86.1%, Staphylococcus – 63.2%, Streptococcus – 54.1%, Candida – 69.3%; in men, Streptococcus were found in 83.0%, Staphylococcus – 79.4%, Corynebacterium – 54.2% and Candida – 37.6% of the cases. Share of obligate anaerobes was also quite large: women were diagnosed with Prevotella in 59.7%, Peptostreptococcus in 53.2%, Fusobacterium in 45.4% of the cases cases; men were observed to have Peptostreptococcus 62.4%, Clostridium in 54.3%, Bacteroides in 32.5% of the cases. We determined high parameters of frequency of diagnosing antibiotic-resistant isolates of conditionally pathogenic microorganisms that circulate in the urogenital tract of patients with dysbiotic impairments, belonging to the following families: Mycoplasmataceae – 78.6%, Enterobacteriaceae – 56.0% and genera – Staphylococcus – 76.1%, Gardnerella – 24.3%, Corynebacterium – 21.2%. The research revealed increase in the frequency of detection of strains of urapathogenic bacteria resistant to the applied antibiotic preparations in 2018–2019 compared with the data of 2017: increases of 10.3% and 6.4% in representatives of family Mycoplasmataceae resistant to ciprofloxacin and ofloxacin respectively, 4.8% and 4.0% in Enterobacteriaceae resistant to chloramphenicol and ampicillin respectively, and 8.9% in the genus Staphylococcus resistant to vancomycin.

Vaginal Microbiome in Preterm Rupture of Membranes

There is an association between vaginal microbiota dysbiosis and preterm premature rupture of membranes (PPROM). In PPROM, reduced Lactobacillus spp abundance is linked to the emergence of high-risk vaginal microbiota, close to the time of membrane rupture. Although PPROM itself can change vaginal microbial composition, antibiotic therapy profoundly effects community structure. Erythromycin may have a beneficial effect in women deplete in Lactobacillus spp but damages a healthy microbiome by targeting Lactobacillus spp. Increased rates of chorioamnionitis and early-onset neonatal sepsis are associated with vaginal microbiota dysbiosis close to the time of delivery.

The pregnancy microbiome and preterm birth

Preterm birth is a global health concern and continues to contribute to substantial neonatal morbidity and mortality despite advances in obstetric and neonatal care. The underlying aetiology is multi-factorial and remains incompletely understood. In this review, the complex interplay between the vaginal microbiome in pregnancy and its association with preterm birth is discussed in depth. Advances in the study of bacteriology and an improved understanding of the human microbiome have seen an improved awareness of the vaginal microbiota in both health and in disease.