In vitro biofilm formation of Gardnerella vaginalis and Escherichia coli associated with bacterial vaginosis and aerobic vaginitis

Objective

To determine the optimum biofilm formation ratio of Gardnerella vaginalis (G. vaginalis) in a mixed culture with Escherichia coli (E. coli).

Methods

G. vaginalis ATCC14018, E. coli ATCC25922, as well as five strains of G. vaginalis were selected from the vaginal sources of patients whose biofilm forming capacity was determined by the Crystal Violet method. The biofilm forming capacity of E. coli in anaerobic and non-anaerobic environments were compared using the identical assay. The Crystal Violet method was also used to determine the biofilm forming capacity of a co-culture of G. vaginalis and E. coli in different ratios. After Live/Dead staining, biofilm thickness was measured using confocal laser scanning microscopy, and biofilm morphology was observed by scanning electron microscopy.

Results

The biofilm forming capacity of E. coli under anaerobic environment was similar to that in a 5% CO2 environment. The biofilm forming capacity of G. vaginalis and E. coli was stronger at 106:105 CFU/mL than at other ratios (P<0.05). Their thicknesses were greater at 106:105 CFU/mL than at the other ratios, with the exception of 106:102 CFU/mL (P<0.05), under laser scanning microscopy. Scanning electron microscopy revealed increased biofilm formation at 106:105 CFU/mL and 106:102 CFU/mL, but no discernible E. coli was observed at 106:102 CFU/mL.

Conclusion

G. vaginalis and E. coli showed the greatest biofilm forming capacity at a concentration of 106:105 CFU/mL at 48 hours and could be used to simulate a mixed infection of bacterial vaginosis and aerobic vaginitis in vitro.

Mechanistic Insights into Immune Suppression and Evasion in Bacterial Vaginosis

The immunological response to bacterial vaginosis (BV) remains poorly understood and recurrent BV is still a major public health burden especially in the pregnant population. This article reviews the potential mechanisms by which BV-associated bacteria suppress and circumvent the host and microbial defence responses, and propagate their survival/dominance without overt inflammation. We discuss the composition of cervicovaginal mucosal barrier and the mechanism by which BV circumvents host defence: the degradation of the mucosal barrier and immunoglobulin A (IgA); the BV-associated organism Gardnerella vaginalis haemolysin (vaginolysin); diminished IgA response against vaginolysin; mucosal sialic acid degradation, foraging and depletion; inhibition of IL-8-induced neutrophilic infiltration; and metabolite-induced incapacitation of neutrophil and monocyte chemotaxis. We also highlight the tolerance/resistance to both host and antimicrobial molecules mounted by BV-associated biofilms. A plausible role of sialic acid-binding immunoglobulin-like lectins (SIGLECS) was also suggested. Sialidase, which is often produced by G. vaginalis, is central to the immunosuppression, relapse and recurrence observed in BV, although it is supported by other hydrolytic enzymes, vaginolysin and immunomodulatory metabolites.

The impact of biological sex on diseases of the urinary tract

Biological sex, being female or male, broadly influences diverse immune phenotypes, including immune responses to diseases at mucosal surfaces. Sex hormones, sex chromosomes, sexual dimorphism, and gender differences all contribute to how an organism will respond to diseases of the urinary tract, such as bladder infection or cancer. Although the incidence of urinary tract infection is strongly sex biased, rates of infection change over a lifetime in women and men, suggesting that accompanying changes in the levels of sex hormones may play a role in the response to infection. Bladder cancer is also sex biased in that 75% of newly diagnosed patients are men. Bladder cancer development is shaped by contributions from both sex hormones and sex chromosomes, demonstrating that the influence of sex on disease can be complex. With a better understanding of how sex influences disease and immunity, we can envision sex-specific therapies to better treat diseases of the urinary tract and potentially diseases of other mucosal tissues.

Bladder Exposure to Gardnerella Activates Host Pathways Necessary for Escherichia coli Recurrent UTI

Recurrent urinary tract infections (rUTI) are a costly clinical problem affecting millions of women worldwide each year. The majority of rUTI cases are caused by uropathogenic Escherichia coli (UPEC). Data from humans and mouse models indicate that some instances of rUTI are caused by UPEC emerging from latent reservoirs in the bladder. Women with vaginal dysbiosis, typically characterized by high levels of Gardnerella and other anaerobes, are at increased risk of UTI. Multiple studies have detected Gardnerella in urine collected by transurethral catheterization (to limit vaginal contamination), suggesting that some women experience routine urinary tract exposures. We recently reported that inoculation of Gardnerella into the bladder triggers rUTI from UPEC bladder reservoirs in a mouse model. Here we performed whole bladder RNA-seq to identify host pathways involved in Gardnerella-induced rUTI. We identified a variety host pathways differentially expressed in whole bladders following Gardnerella exposure, such as pathways involved in inflammation/immunity and epithelial turnover. At the gene level, we identified upregulation of Immediate Early (IE) genes, which are induced in various cell types shortly following stimuli like infection and inflammation. One such upregulated IE gene was the orphan nuclear receptor Nur77 (aka Nr4a1). Pilot experiments in Nur77-/- mice suggest that Nur77 is necessary for Gardnerella exposure to trigger rUTI from UPEC reservoirs. These findings demonstrate that bladder gene expression can be impacted by short-lived exposures to urogenital bacteria and warrant future examination of responses in distinct cell types, such as with single cell transcriptomic technologies. The biological validation studies in Nur77-/- mice lay the groundwork for future studies investigating Nur77 and the Immediate Early response in rUTI.

Recent Advances in Presentation, Diagnosis and Treatment for Mixed Vaginitis

Mixed vaginitis is the simultaneous presence of at least two types of vaginitis, contributing to an abnormal vaginal milieu and leading to vaginal symptoms and signs. However, associations between symptoms and the type of mixed vaginitis have not been clearly elucidated, and research on mixed vaginitis is still in the preliminary stage. Therefore, the pathogenic mechanism of mixed vaginitis remains understudied. Mixed vaginitis generally involves the formation of mixed biofilms. The study of polymicrobial interactions and mixed biofilms will provide a new idea for the understanding of mixed vaginitis. Moreover, this review summarizes some effective management and laboratory diagnosis of mixed vaginitis to avoid inappropriate therapy, recurrence, and reinfection. It is of high clinical importance to obtain relevant clinical data to improve clinical knowledge about mixed vaginitis.

The Role of 17β-Estrogen in Escherichia coli Adhesion on Human Vaginal Epithelial Cells via FAK Phosphorylation

Estrogen, the predominant sex hormone, has been found to be related to the occurrence of vaginal infectious diseases. However, its role in the occurrence and development of bacterial vaginitis caused by Escherichia coli is still unclear. The objective of this study was to investigate the role of 17β-estrogen in E. coli adhesion on human vaginal epithelial cells. The vaginal epithelial cell line VK2/E6E7 was used to study the molecular events induced by estrogen between E. coli and cells. An adhesion study was performed to evaluate the involvement of the estrogen-dependent focal adhesion kinase (FAK) activation with cell adhesion. The phosphorylation status of FAK and estrogen receptor α (ERα) upon estrogen challenge was assessed by Western blotting. Specific inhibitors for ERα were used to validate the involvement of ERα-FAK signaling cascade. The results showed that, following stimulation with 1,000 nM estrogen for 48 h, transient activation of ERα and FAK was observed, as was an increased average number of E. coli cells adhering to vaginal epithelial cells. In addition, estrogen-induced activation of ERα and FAK was inhibited by the specific inhibitor of ERα, especially when the inhibitor reached a 10 μM concentration and acted for 1 h, and a decrease in the number of adherent E. coli cells was observed simultaneously. However, this inhibitory effect diminished as the concentration of estrogen increased. In conclusion, FAK and ERα signaling cascades were associated with the increasing E. coli adherence to vaginal epithelial cells, which was promoted by a certain concentration of estrogen.

The Vaginal Microbiota, Bacterial Biofilms and Polymeric Drug-Releasing Vaginal Rings

The diversity and dynamics of the microbial species populating the human vagina are increasingly understood to play a pivotal role in vaginal health. However, our knowledge about the potential interactions between the vaginal microbiota and vaginally administered drug delivery systems is still rather limited. Several drug-releasing vaginal ring products are currently marketed for hormonal contraception and estrogen replacement therapy, and many others are in preclinical and clinical development for these and other clinical indications. As with all implantable polymeric devices, drug-releasing vaginal rings are subject to surface bacterial adherence and biofilm formation, mostly associated with endogenous microorganisms present in the vagina. Despite more than 50 years since the vaginal ring concept was first described, there has been only limited study and reporting around bacterial adherence and biofilm formation on rings. With increasing interest in the vaginal microbiome and vaginal ring technology, this timely review article provides an overview of: (i) the vaginal microbiota, (ii) biofilm formation in the human vagina and its potential role in vaginal dysbiosis, (iii) mechanistic aspects of biofilm formation on polymeric surfaces, (iv) polymeric materials used in the manufacture of vaginal rings, (v) surface morphology characteristics of rings, (vi) biomass accumulation and biofilm formation on vaginal rings, and (vii) regulatory considerations.

Genome Investigation of Urinary Gardnerella Strains and Their Relationship to Isolates of the Vaginal Microbiota

Gardnerella is a frequent member of the urogenital microbiota. Given the association between Gardnerella vaginalis and bacterial vaginosis (BV), significant efforts have been focused on characterizing this species in the vaginal microbiota. However, Gardnerella also is a frequent member of the urinary microbiota. In an effort to characterize the bacterial species of the urinary microbiota, we present here 10 genomes of urinary Gardnerella isolates from women with and without lower urinary tract symptoms. These genomes complement those of 22 urinary Gardnerella strains previously isolated and sequenced by our team. We included these genomes in a comparative genome analysis of all publicly available Gardnerella genomes, which include 33 urinary isolates, 78 vaginal isolates, and 2 other isolates. While once this genus was thought to consist of a single species, recent comparative genome analyses have revealed 3 new species and an additional 9 groups within Gardnerella Based upon our analysis, we suggest a new group for the species. We also find that distinction between these Gardnerella species/groups is possible only when considering the core or whole-genome sequence, as neither the sialidase nor vaginolysin genes are sufficient for distinguishing between species/groups despite their clinical importance. In contrast to the vaginal microbiota, we found that only five Gardnerella species/groups have been detected within the lower urinary tract. Although we found no association between a particular Gardnerella species/group(s) and urinary symptoms, further sequencing of urinary Gardnerella isolates is needed for both comprehensive taxonomic characterization and etiological classification of Gardnerella in the urinary tract.IMPORTANCE Prior research into the bacterium Gardnerella vaginalis has largely focused on its association with bacterial vaginosis (BV). However, G. vaginalis is also frequently found within the urinary microbiota of women with and without lower urinary tract symptoms as well as individuals with chronic kidney disease, interstitial cystitis, and BV. This prompted our investigation into Gardnerella from the urinary microbiota and all publicly available Gardnerella genomes from the urogenital tract. Our work suggests that while some Gardnerella species can survive in both the urinary tract and vagina, others likely cannot. This study provides the foundation for future studies of Gardnerella within the urinary tract and its possible contribution to lower urinary tract symptoms.

Atopobium vaginae and Prevotella bivia Are Able to Incorporate and Influence Gene Expression in a Pre-Formed Gardnerella vaginalis Biofilm

Bacterial vaginosis (BV) is associated with a highly structured polymicrobial biofilm on the vaginal epithelium where Gardnerella species presumably play a pivotal role. Gardnerella vaginalis, Atopobium vaginae, and Prevotella bivia are vaginal pathogens detected during the early stages of incident BV. Herein, we aimed to analyze the impact of A. vaginae and P. bivia on a pre-established G. vaginalis biofilm using a novel in vitro triple-species biofilm model. Total biofilm biomass was determined by the crystal violet method. We also discriminated the bacterial populations in the biofilm and in its planktonic fraction by using PNA FISH. We further analyzed the influence of A. vaginae and P. bivia on the expression of key virulence genes of G. vaginalis by quantitative PCR. In our tested conditions, A. vaginae and P. bivia were able to incorporate into pre-established G. vaginalis biofilms but did not induce an increase in total biofilm biomass, when compared with 48-h G. vaginalis biofilms. However, they were able to significantly influence the expression of HMPREF0424_0821, a gene suggested to be associated with biofilm maintenance in G. vaginalis. This study suggests that microbial relationships between co-infecting bacteria can deeply affect the G. vaginalis biofilm, a crucial marker of BV.

Cervical Gardnerella vaginalis in women with preterm prelabor rupture of membranes

Objective

To determine the association between microbial invasion of the amniotic cavity (MIAC) and/or intra-amniotic inflammation (IAI) and the cervical prevalence of Gardnerella vaginalis DNA in pregnancies with preterm prelabor rupture of membrane (PPROM).

Method

In total, 405 women with singleton pregnancies complicated with PPROM were included. Cervical fluid and amniotic fluid samples were collected at the time of admission. Bacterial and G. vaginalis DNA were assessed in the cervical fluid samples using quantitative PCR technique. Concentrations of interleukin-6 and MIAC were evaluated in the amniotic fluid samples. Loads of G. vaginalis DNA ≥ 1% of the total cervical bacterial DNA were used to define the cervical prevalence of G. vaginalis as abundant. Based on the MIAC and IAI, women were categorized into four groups: with intra-amniotic infection (both MIAC and IAI), with sterile IAI (IAI without MIAC), with MIAC without IAI, and without either MIAC or IAI.

Results

The presence of the abundant cervical G. vaginalis was related to MIAC (with: 65% vs. without: 44%; p = 0.0004) but not IAI (with: 52% vs. without: 48%; p = 0.70). Women with MIAC without IAI had the highest load of the cervical G. vaginalis DNA (median 2.0 × 10⁴ copies DNA/mL) and the highest presence of abundant cervical G. vaginalis (73%).

Conclusions

In women with PPROM, the presence of cervical G. vaginalis was associated with MIAC, mainly without the concurrent presence of IAI.

Comparative analysis of Bacterial Vaginosis microbiota among pregnant and non-pregnant females and isolation of phages against Enterococcus faecalis, Enterococcus faecium, and Shigella flexneri strains

BACKGROUND AND OBJECTIVES

Bacterial vaginosis (BV) is the most common vaginal infection in women of reproductive age. It shifts the paradigms of the vagina from healthy, beneficial microbiota to facultative and strict anaerobes. BV remains one of the most arduous and controversial challenges in modern-day clinical microbiology because of its high prevalence and relapse rates. A lot of research has been carried out on it. Still, its etiology is unknown, which gave this infection global importance. The current study was designed to investigate and compare the microbiota of pregnant and non-pregnant females suffering from BV, and phages were isolated against BV microbiota.

MATERIAL AND METHODS

The samples were collected from the vagina by using a speculum, and swabs were streaked on different media to isolate bacteria. The microbiological analysis was performed by microscopy, biochemical testing, and antibiotic susceptibility was determined by using Metronidazole and Clindamycin. Furthermore, the phages were isolated and characterized against BV strains.

RESULTS AND CONCLUSION

The Gram staining showed high prevalence of Staphylococcus (36% vs. 33%), followed by Streptococcus (31% vs. 14%) and Enterococcus (7% vs. 14%) in non-pregnant and pregnant females' respectively. However, the exception was observed in non-pregnant BV positive females, who had Shigella flexneri in their samples. The antibiotic sensitivity showed Metronidazole was resistant against all BV microbiota, and Clindamycin showed susceptibility against 3 strains. Phages were isolated against three bacterial strains, i.e. E. faecalis, E. faecium, and S. flexneri. Bacterial reduction assay showed bacterial growth decreases in the presence of phage suspension, pH stability showed phages' maximum lytic activity at pH 7 for E. faecalis and E. faecium and pH 9 for S. flexneri. However, the thermal stability showed phages' highest lytic activity at 55 °C for E. faecalis, 70 °C for E. faecium, and 40 °C for S. flexneri. Phage genome isolation showed that all phages nucleic acid was DNA in nature and between 15 and 20kbp. SEM analysis showed they were circular in shape and might belong to the Podoviridae family. This study provides an understanding of pathogens involved in BV and helps the doctors to treat the patients accordingly. Furthermore, this study showed that Bacterial Vaginosis and BV secondary bacteria have associations. BV secondary microbiota is also involved in the pathogenesis of this infection, whereas bacteriophage therapy has the potential to be used as an alternative treatment to antibiotics.

Gardnerella and vaginal health: the truth is out there

The human vagina is a dynamic ecosystem in which homeostasis depends on mutually beneficial interactions between the host and their microorganisms. However, the vaginal ecosystem can be thrown off balance by a wide variety of factors. Bacterial vaginosis (BV) is the most common vaginal infection in women of childbearing age but its etiology is not yet fully understood, with different controversial theories being raised over the years. What is generally accepted is that BV is often characterized by a shift in the composition of the normal vaginal microbiota, from a Lactobacillus species dominated microbiota to a mixture of anaerobic and facultative anaerobic bacteria. During BV, a polymicrobial biofilm develops in the vaginal microenvironment, being mainly composed of Gardnerella species. The interactions between vaginal microorganisms are thought to play a pivotal role in the shift from health to disease and might also increase the risk of sexually transmitted infections acquisition. Here, we review the current knowledge regarding the specific interactions that occur in the vaginal niche and discuss mechanisms by which these interactions might be mediated. Furthermore, we discuss the importance of novel strategies to fight chronic vaginal infections.

Bacterial Vaginosis: Current Diagnostic Avenues and Future Opportunities

A healthy female genital tract harbors a microbiome dominated by lactic acid and hydrogen peroxide producing bacteria, which provide protection against infections by maintaining a low pH. Changes in the bacterial compositions of the vaginal microbiome can lead to bacterial vaginosis (BV), which is often associated with vaginal inflammation. Bacterial vaginosis increases the risk of acquiring sexually transmitted infections (STIs) like human immunodeficiency virus (HIV) and affects women's reproductive health negatively. In pregnant women, BV can lead to chorioamnionitis and adverse pregnancy outcomes, including preterm premature rupture of the membranes and preterm birth. In order to manage BV effectively, good diagnostic procedures are required. Traditionally clinical and microscopic methods have been used to diagnose BV; however, these methods require skilled staff and time and suffer from reduced sensitivity and specificity. New diagnostics, including highly sensitive and specific point-of-care (POC) tests, treatment modalities and vaccines can be developed based on the identification of biomarkers from the growing pool of vaginal microbiome and vaginal metabolome data. In this review the current and future diagnostic avenues will be discussed.

Unveiling the role of Gardnerella vaginalis in polymicrobial Bacterial Vaginosis biofilms: the impact of other vaginal pathogens living as neighbors

Bacterial vaginosis (BV) is characterized by a highly structured polymicrobial biofilm, which is strongly adhered to the vaginal epithelium and primarily consists of the bacterium Gardnerella vaginalis. However, despite the presence of other BV-associated bacteria, little is known regarding the impact of other species on BV development. To gain insight into BV progress, we analyzed the ecological interactions between G. vaginalis and 15 BV-associated microorganisms using a dual-species biofilm model. Bacterial populations were quantified using a validated peptide nucleic acid fluorescence in situ hybridization approach. Furthermore, biofilm structure was analyzed by confocal laser scanning microscopy. In addition, bacterial coaggregation ability was determined as well as the expression of key virulence genes. Remarkably, our results revealed distinct biofilm structures between each bacterial consortium, leading to at least three unique dual-species biofilm morphotypes. Furthermore, our transcriptomic findings seem to indicate that Enterococcus faecalis and Actinomyces neuii had a higher impact on the enhancement of G. vaginalis virulence, while the other tested species had a lower or no impact on G. vaginalis virulence. This study casts a new light on how BV-associated species can modulate the virulence aspects of G. vaginalis, contributing to a better understanding of the development of BV-associated biofilms.

Influence of co-infection complicated with human papillomavirus on cervical intraepithelial neoplasia development in patients with atypical squamous cells of undetermined significance

AIM

Human papillomaviruses (HPV) infection is a primary cause of the development of cervical precancerous lesions and cervical cancer. However, the influence of other infections on intraepithelial neoplasia (CIN) development has not been fully elucidated. We evaluated the association between co-infection and CIN development in subjects with atypical squamous cells of undetermined significance (ASCUS).

METHOD

Data for ASCUS subjects who had undergone testing for high risk HPV (HR-HPV) and pathological diagnosis were analyzed. From the CIN grade, HR-HPV and vaginal infection (VI) data, both the relationship between HPV infection and CIN development and the influence of co-infection on CIN were retrospectively evaluated.

RESULTS

Data for 56 ASCUS subjects who had undergone HR-HPV testing and cytological diagnosis were analyzed. Positive rates were HPV (73.2%), HPV16 (21.4%), HPV18 (7.1%), and HPV16 and/or 18 (26.8%). Seventeen of the subjects were diagnosed as having one or more VI pathogen; the major pathogens found were Candida spp., Gardnerella vaginalis, group B streptococcus, coagulase negative Staphylococcus, and Chlamydia trachomatis. The rate of CIN 2 or worse (≥CIN 2) was significantly higher in subjects positive for HPV16 compared with HPV negative subjects, and was significantly higher in subjects with a VI complicated with HPV compared to those without a VI. Univariate and multivariate logistic regression analysis identified positive for HPV16 and/or 18 and positive for VI to be significant variables for ≥ CIN 2.

CONCLUSION

Our results indicate that having a vaginal infection complicated with HR-HPV affects the development of CIN in subjects with ASCUS cytology.

Women and Their Microbes: The Unexpected Friendship

Communities of microbiota have been associated with numerous health outcomes, and while much emphasis has been placed on the gastrointestinal niche, there is growing interest in the microbiome specific for female reproductive health and the health of their offspring. The vaginal microbiome plays an essential role not only in health and dysbiosis, but also potentially in successful fertilization and healthy pregnancies. In addition, microbial communities have been isolated from formerly forbidden sterile niches such as the placenta, breast, uterus, and Fallopian tubes, strongly suggesting an additional microbial role in women's health. A combination of maternally linked prenatal, birth, and postnatal factors, together with environmental and medical interventions, influence early and later life through the microbiome. Here, we review the role of microbes in female health focusing on the vaginal tract and discuss how male and female reproductive microbiomes are intertwined with conception and how mother-child microbial transfer is a key determinant in infant health, and thus the next generation.

Etiology of bacterial vaginosis and polymicrobial biofilm formation

Microorganisms in nature rarely exist in a planktonic form, but in the form of biofilms. Biofilms have been identified as the cause of many chronic and persistent infections and have been implicated in the etiology of bacterial vaginosis (BV). Bacterial vaginosis is the most common form of vaginal infection in women of reproductive age. Similar to other biofilm infections, BV biofilms protect the BV-related bacteria against antibiotics and cause recurrent BV. In this review, an overview of BV-related bacteria, conceptual models and the stages involved in the polymicrobial BV biofilm formation will be discussed.