Determination of immunoglobulin A against Gardnerella vaginalis hemolysin, sialidase, and prolidase activities in vaginal fluid: implications for adverse pregnancy outcomes

The role of sialidases in the pathogenesis of bacterial vaginosis and their use as a promising pharmacological target in bacterial vaginosis

Bacterial vaginosis (BV) is an infection of the genital tract characterized by disturbance of the normally Lactobacilli-dominated vaginal flora due to the overgrowth of Gardnerella and other anaerobic bacteria. Gardnerella vaginalis, an anaerobic pathogen and the major pathogen of BV, produces sialidases that cleave terminal sialic acid residues off of human glycans. By desialylation, sialidases not only alter the function of sialic acid-containing glycoconjugates but also play a vital role in the attachment, colonization and spread of many other vaginal pathogens. With known pathogenic effects, excellent performance of sialidase-based diagnostic tests, and promising therapeutic potentials of sialidase inhibitors, sialidases could be used as a biomarker of BV. This review explores the sources of sialidases and their role in vaginal dysbiosis, in aims to better understand their participation in the pathogenesis of BV and their value in the diagnosis and treatment of BV.

Antibody Response to the Sneathia vaginalis Cytopathogenic Toxin A during Pregnancy

Sneathia vaginalis is a Gram-negative vaginal species that is associated with pregnancy complications. It produces cytopathogenic toxin A (CptA), a pore-forming toxin. To determine whether CptA is expressed in vivo and to examine the mucosal Ab response to the toxin, we examined human midvaginal swab samples obtained during pregnancy for IgM, IgA, and IgG Abs with CptA affinity. This subcohort study included samples from 93 pregnant people. S. vaginalis relative abundance was available through 16S rRNA survey. There were 22 samples from pregnancies that resulted in preterm birth in which S. vaginalis relative abundance was <0.005%, 22 samples from pregnancies that resulted in preterm birth with S. vaginalis ≥0.005%, 24 samples from pregnancies that resulted in term birth with S. vaginalis <0.005%, and 25 samples from pregnancies that resulted in term birth with S. vaginalis ≥0.005%. IgM, IgA, and IgG with affinity for CptA were assessed by ELISA. The capacity for the samples to neutralize CptA was quantified by hemolysis assay. All three Ab isotypes were detectable within different subsets of the samples. There was no significant association between relative abundance of S. vaginalis and the presence of any Ab isotype. The majority of vaginal swab samples containing detectable levels of anti-CptA Abs neutralized the hemolytic activity of CptA, with the strongest correlation between IgA and neutralizing activity. These results demonstrate that S. vaginalis produces CptA in vivo and that CptA is recognized by the host immune defenses, resulting in the production of Abs with toxin-neutralizing ability.

Cervicovaginal Gardnerella sialidase-encoding gene in persistent human papillomavirus infection

Disturbed vaginal microbiota have a role in the persistence of high-oncogenic-risk human papillomavirus (hrHPV) and Gardnerella spp. is closely related with this condition. Such bacteria are the major source of cervicovaginal sialidases, important for microbiota alterations. The sialidase-encoding gene nanH3 is account for their sialidase activity. Thus, a subset of 212 women positive for hrHPV at the first visit were included in the analysis of the current study aiming to compare the loads of nanH3 in cervicovaginal fluid (CFV) of women with persistent hrHPV infection and with those cleared the infection after a year. Participants were assigned to two study groups named "persistence" (n = 124, 53.22%) or "clearance" (n = 88, 37.77%), according to the HPV status upon enrollment and follow-up. Absolute quantification of nanH3 gene was performed using quantitative real-time PCR (qPCR). Persistence and clearance group did not show statistical difference in the load of nanH3 gene (p = 0.19). When considering the subset of women with HPV16, differences in number of copies of nanh3 gene was observed between the persistent (7.39E+08 copies/μL) and clearance group (2.85E+07 copies/μL) (p = 0.007). Therefore, baseline loads of nanH3 gene is increased in women that persist with cervical HPV16 infection after 12 months.

Ureaplasma parvum infection induces inflammatory changes in vaginal epithelial cells independent of sialidase

BACKGROUND

Ureaplasma, a genus of the order Mycoplasmatales and commonly grouped with Mycoplasma as genital mycoplasma is one of the most common microbes isolated from women with infection/inflammation-associated preterm labor (PTL). Mycoplasma spp. produce sialidase that cleaves sialic acid from glycans of vaginal mucous membranes and facilitates adherence and invasion of the epithelium by pathobionts, and dysregulated immune response. However, whether Ureaplasma species can induce the production of sialidase is yet to be demonstrated. We examined U. parvum-infected vaginal epithelial cells (VECs) for the production of sialidase and pro-inflammatory cytokines.

METHODS

Immortalized VECs were cultured in appropriate media and treated with U. parvum in a concentration of 1 × 10⁵ DNA copies/ml. After 24 h of treatment, cells and media were harvested. To confirm infection and cell uptake, immunocytochemistry for multi-banded antigen (MBA) was performed. Pro-inflammatory cytokine production and protein analysis for sialidase confirmed pro-labor pathways.

RESULTS

Infection of VECs was confirmed by the presence of intracellular MBA. Western blot analysis showed no significant increase in sialidase expression from U. parvum-treated VECs compared to uninfected cells. However, U. parvum infection induced 2-3-fold increased production of GM-CSF (p = 0.03), IL-6 (p = 0.01), and IL-8 (p = 0.01) in VECs compared to controls.

CONCLUSION

U. parvum infection of VECs induced inflammatory imbalance associated with vaginal dysbiosis but did not alter sialidase expression at the cellular level. These data suggest that U. parvum's pathogenic effect could be propagated by locally produced pro-inflammatory cytokines and, unlike other genital mycoplasmas, may be independent of sialidase.

Antibiotic resistance and pathogenicity assessment of various Gardnerella sp. strains in local China

Gardnerella overgrowth is the primary cause of bacterial vaginosis (BV), a common vaginal infection with incidences as high as 23–29% worldwide. Here, we studied the pathogenicity, drug resistance, and prevalence of varying Gardnerella spp. We isolated 20 Gardnerella strains from vaginal samples of 31 women in local China. Ten strains were then selected via phylogenetic analysis of cpn60 and vly gene sequences to carry out genome sequencing and comparative genomic analysis. Biofilm-formation, sialidase, and antibiotic resistance activities of the strains were characterized. All strains showed striking heterogeneity in genomic structure, biofilm formation and drug resistance. Two of the ten strains, JNFY3 and JNFY15, were classified as Gardnerella swidsinskii and Gardnerella piotii, respectively, according to their phenotypic characteristics and genome sequences. In particular, seven out of the ten strains exhibited super resistance (≥ 128 μg/mL) to metronidazole, which is the first line of treatment for BV in China. Based on the biochemical and genomic results of the strains, we proposed a treatment protocol of prevalent Gardnerella strains in local China, which provides the basis for accurate diagnosis and therapy.

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.

Enhanced IgA coating of bacteria in women with Lactobacillus crispatus-dominated vaginal microbiota

BACKGROUND

Immunoglobulin A (IgA) plays an important role in maintaining a healthy intestinal microbiome, but little is known about the interaction between local immunoglobulins and the vaginal microbiome. We assessed immunoglobulins (unbound and bound to bacteria), their association with vaginal microbiota composition and the changes over time in 25 healthy women of reproductive age.

RESULTS

In both Lactobacillus crispatus-dominated and non-L. crispatus-dominated microbiota, IgA and IgG (unbound and bound to bacteria) were higher during menses (T = 1) compared to day 7‑11 (T = 2) and day 17‑25 (T = 3) after menses onset. The majority of vaginal bacteria are coated with IgA and/or IgG. Women with L. crispatus-dominated microbiota have increased IgA coating of vaginal bacteria compared to women with other microbiota compositions, but contained less IgA per bacterium. Presence of a dominantly IgA-coated population at T = 2 and/or T = 3 was also strongly associated with L. crispatus-dominated microbiota. In women with non-L. crispatus-dominated microbiota, more bacteria were uncoated. Unbound IgA, unbound IgG, and bound IgG levels were not associated with microbiota composition.

CONCLUSIONS

In conclusion, L. crispatus-dominated vaginal microbiota have higher levels of bacterial IgA coating compared to non-L. crispatus-dominated vaginal microbiota. Similar to its regulating function in the intestinal tract, we hypothesize that IgA is involved in maintaining L. crispatus-dominated microbiota in the female genital tract. This may play a role in L. crispatus-associated health benefits. Video abstract.

Large-scale characterisation of the pregnancy vaginal microbiome and sialidase activity in a low-risk Chinese population

Vaginal microbiota-host interactions are linked to preterm birth (PTB), which continues to be the primary cause of global childhood mortality. Due to population size, the majority of PTB occurs in Asia, yet there have been few studies of the pregnancy vaginal microbiota in Asian populations. Here, we characterized the vaginal microbiome of 2689 pregnant Chinese women using metataxonomics and in a subset (n = 819), the relationship between vaginal microbiota composition, sialidase activity and leukocyte presence and pregnancy outcomes. Vaginal microbiota were most frequently dominated by Lactobacillus crispatus or L. iners, with the latter associated with vaginal leukocyte presence. Women with high sialidase activity were enriched for bacterial vaginosis-associated genera including Gardnerella, Atopobium and Prevotella. Vaginal microbiota composition, high sialidase activity and/or leukocyte presence was not associated with PTB risk suggesting underlying differences in the vaginal microbiota and/or host immune responses of Chinese women, possibly accounting for low PTB rates in this population.

The Female Vaginal Microbiome in Health and Bacterial Vaginosis

The vaginal microbiome is an intricate and dynamic microecosystem that constantly undergoes fluctuations during the female menstrual cycle and the woman’s entire life. A healthy vaginal microbiome is dominated by Lactobacillus which produce various antimicrobial compounds. Bacterial vaginosis (BV) is characterized by the loss or sharp decline in the total number of Lactobacillus and a corresponding marked increase in the concentration of anaerobic microbes. BV is a highly prevalent disorder of the vaginal microbiota among women of reproductive age globally. BV is confirmed to be associated with adverse gynecologic and obstetric outcomes, such as sexually transmitted infections, pelvic inflammatory disease, and preterm birth. Gardnerella vaginalis is the most common microorganism identified from BV. It is the predominant microbe in polymicrobial biofilms that could shelter G. vaginalis and other BV-associated microbes from adverse host environments. Many efforts have been made to increase our understanding of the vaginal microbiome in health and BV. Thus, improved novel and accurate diagnosis and therapeutic strategies for BV have been developed. This review covers the features of vaginal microbiome, BV, BV-associated diseases, and various strategies of diagnosis and treatment of BV, with an emphasis on recent research progresses.

Vaginal sialoglycan foraging by Gardnerella vaginalis: mucus barriers as a meal for unwelcome guests?

Bacterial vaginosis (BV) is a condition of the vaginal microbiome in which there are few lactobacilli and abundant anaerobic bacteria. Members of the genus Gardnerella are often one of the most abundant bacteria in BV. BV is associated with a wide variety of poor health outcomes for women. It has been recognized since the 1980s that women with BV have detectable and sometimes markedly elevated levels of sialidase activity in vaginal fluids and that bacteria associated with this condition produce this activity in culture. Mounting evidence collected using diverse methodologies points to the conclusion that BV is associated with a reduction in intact sialoglycans in cervicovaginal secretions. Here we review evidence for the contributions of vaginal bacteria, especially Gardnerella, in the processes of mucosal sialoglycan degradation, uptake, metabolism and depletion. Our understanding of the impacts of vaginal sialoglycan degradation is still limited. However, the potential implications of sialic acid depletion are discussed in light of our current understanding of the roles played by sialoglycans in vaginal physiology.

A specific bacterial DNA signature in the vagina of Australian women in midpregnancy predicts high risk of spontaneous preterm birth (the Predict1000 study)

BACKGROUND

Intrauterine infection accounts for a quarter of the cases of spontaneous preterm birth; however, at present, it is not possible to efficiently identify pregnant women at risk to deliver preventative treatments.

OBJECTIVE

This study aimed to establish a vaginal microbial DNA test for Australian women in midpregnancy that will identify those at increased risk of spontaneous preterm birth.

STUDY DESIGN

A total of 1000 women with singleton pregnancies were recruited in Perth, Australia. Midvaginal swabs were collected between 12 and 23 weeks' gestation. DNA was extracted for the detection of 23 risk-related microbial DNA targets by quantitative polymerase chain reaction. Obstetrical history, pregnancy outcome, and demographics were recorded.

RESULTS

After excluding 64 women owing to losses to follow-up and insufficient sample for microbial analyses, the final cohort consisted of 936 women of predominantly white race (74.3%). The overall preterm birth rate was 12.6% (118 births); the spontaneous preterm birth rate at <37 weeks' gestation was 6.2% (2.9% at ≤34 weeks' gestation), whereas the preterm premature rupture of the membranes rate was 4.2%. No single individual microbial target predicted increased spontaneous preterm birth risk. Conversely, women who subsequently delivered at term had higher amounts of Lactobacillus crispatus, Lactobacillus gasseri, or Lactobacillus jensenii DNA in their vaginal swabs (13.8% spontaneous preterm birth vs 31.2% term; P=.005). In the remaining women, a specific microbial DNA signature was identified that was strongly predictive of spontaneous preterm birth risk, consisting of DNA from Gardnerella vaginalis (clade 4), Lactobacillus iners, and Ureaplasma parvum (serovars 3 and 6). Risk prediction was improved if Fusobacterium nucleatum detection was included in the test algorithm. The final algorithm, which we called the Gardnerella Lactobacillus Ureaplasma (GLU) test, was able to detect women at risk of spontaneous preterm birth at <37 and ≤34 weeks' gestation, with sensitivities of 37.9% and 44.4%, respectively, and likelihood ratios (plus or minus) of 2.22 per 0.75 and 2.52 per 0.67, respectively. Preterm premature rupture of the membranes was more than twice as common in GLU-positive women. Adjusting for maternal demographics, ethnicity, and clinical history did not improve prediction. Only a history of spontaneous preterm birth was more effective at predicting spontaneous preterm birth than a GLU-positive result (odds ratio, 3.6).

CONCLUSION

We have identified a vaginal bacterial DNA signature that identifies women with a singleton pregnancy who are at increased risk of spontaneous preterm birth and may benefit from targeted antimicrobial therapy.

Sequence Comparison of Vaginolysin from Different Gardnerella Species

Gardnerella vaginalis has recently been split into 13 distinct species. In this study, we tested the hypotheses that species-specific variations in the vaginolysin (VLY) amino acid sequence could influence the interaction between the toxin and vaginal epithelial cells and that VLY variation may be one factor that distinguishes less virulent or commensal strains from more virulent strains. This was assessed by bioinformatic analyses of publicly available Gardnerella spp. sequences and quantification of cytotoxicity and cytokine production from purified, recombinantly produced versions of VLY. After identifying conserved differences that could distinguish distinct VLY types, we analyzed metagenomic data from a cohort of female subjects from the Vaginal Human Microbiome Project to investigate whether these different VLY types exhibited any significant associations with symptoms or Gardnerella spp.-relative abundance in vaginal swab samples. While Type 1 VLY was most prevalent among the subjects and may be associated with increased reports of symptoms, subjects with Type 2 VLY dominant profiles exhibited increased relative Gardnerella spp. abundance. Our findings suggest that amino acid differences alter the interaction of VLY with vaginal keratinocytes, which may potentiate differences in bacterial vaginosis (BV) immunopathology in vivo.

Microbiota in vaginal health and pathogenesis of recurrent vulvovaginal infections: a critical review

Recurrent vulvovaginal infections (RVVI) has not only become an epidemiological and clinical problem but also include large social and psychological consequences. Understanding the mechanisms of both commensalism and pathogenesis are necessary for the development of efficient diagnosis and treatment strategies for these enigmatic vaginal infections. Through this review, an attempt has been made to analyze vaginal microbiota (VMB) from scratch and to provide an update on its current understanding in relation to health and common RVVI i.e. bacterial vaginosis, vulvovaginal candidiaisis and Trichomoniasis, making the present review first of its kind. For this, potentially relevant studies were retrieved from data sources and critical analysis of the literature was made. Though, culture-independent methods have greatly unfolded the mystery regarding vaginal bacterial microbiome, there are only a few studies regarding the composition and diversity of vaginal mycobiome and different Trichomonas vaginalis strains. This scenario suggests a need of further studies based on comparative genomics of RVVI pathogens to improve our perceptive of RVVI pathogenesis that is still not clear (Fig. 5). Besides this, the review details the rationale for Lactobacilli dominance and changes that occur in healthy VMB throughout a women’s life. Moreover, the list of possible agents continues to expand and new species recognised in both health and VVI are updated in this review. The review concludes with the controversies challenging the widely accepted dogma i.e. “VMB dominated with Lactobacilli is healthier than a diverse VMB”. These controversies, over the past decade, have complicated the definition of vaginal health and vaginal infections with no definite conclusion. Thus, further studies on newly recognised microbial agents may reveal answers to these controversies. Conversely, VMB of women could be an answer but it is not enough to just look at the microbiology. We have to look at the woman itself, as VMB which is fine for one woman may be troublesome for others. These differences in women’s response to the same VMB may be determined by a permutation of behavioural, cultural, genetic and various other anonymous factors, exploration of which may lead to proper definition of vaginal health and disease.

A Biochemiluminescent Sialidase Assay for Diagnosis of Bacterial Vaginosis

Bacterial vaginosis (BV) is a common condition among women of reproductive age. A sensitive, quantitative and rapid assay is needed for the diagnosis of and, particularly, therapy monitoring for BV. Bacterial sialidase appears to play an important role in bacterial biofilms on vaginal epithelium, a condition closely associated with BV. Here, we report a biochemiluminescent sialidase assay that uses a substrate derivatized with firefly luciferin. In the presence of sialidase in the reaction, the substrate is cleaved to release luciferin, which is subsequently oxidized by firefly luciferase to generate a light signal. Thus, the light signal intensity can be used to detect and measure the relative concentration of sialidase in a vaginal sample as a means of BV diagnosis. All reagents are present in a reagent bead and sample buffer, enabling essentially a one-step assay. The assay is highly sensitive and quantitative, with a sensitivity and specificity of 95.40% and 94.94%, respectively, compared to the Amsel method. Interestingly, only 27.6% of those with BV had high levels of sialidase activity with a signal to cutoff ratio of 10 or more. The assay may be used for diagnosis of BV, risk assessment of BV patients in terms of sialidase activity levels, and monitoring antibiotic therapy.

Gardnerella vaginalis and Prevotella bivia Trigger Distinct and Overlapping Phenotypes in a Mouse Model of Bacterial Vaginosis

BACKGROUND

Bacterial vaginosis (BV) is a common imbalance of the vaginal microbiota characterized by overgrowth of diverse Actinobacteria, Firmicutes, and Gram-negative anaerobes. Women with BV are at increased risk of secondary reproductive tract infections and adverse pregnancy outcomes. However, which specific bacteria cause clinical features of BV is unclear.

METHODS

We previously demonstrated that Gardnerella vaginalis could elicit many BV features in mice. In this study, we established a BV model in which we coinfected mice with G. vaginalis and another species commonly found in women with BV: Prevotella bivia.

RESULTS

This coinfection model recapitulates several aspects of human BV, including vaginal sialidase activity (a diagnostic BV feature independently associated with adverse outcomes), epithelial exfoliation, and ascending infection. It is notable that G. vaginalis facilitated uterine infection by P. bivia.

CONCLUSIONS

Taken together, our model provides a framework for advancing our understanding of the role of individual or combinations of BV-associated bacteria in BV pathogenesis.

Cervicovaginal cytokines, sialidase activity and bacterial load in reproductive-aged women with intermediate vaginal flora

Studies have shown that not only bacterial vaginosis, but also intermediate vaginal flora has deleterious effects for women's reproductive health. However, literature still lacks information about microbiological and immunological aspects of intermediate flora.

OBJECTIVE

To characterize intermediate flora regarding levels of Interleukin (IL)-1beta, IL-6, IL-8, tumor necrosis factor-alpha, interleukin 1 receptor antagonist (IL-1ra), IL-10, sialidase; loads of Gardnerella vaginalis, total bacteria and to verify whether it is closer related to normal flora or bacterial vaginosis. This cross-sectional study enrolled 526 non-pregnant reproductive-aged women distributed in 3 groups according to pattern of vaginal flora using Nugent's system in normal, intermediate and bacterial vaginosis. Cervicovaginal levels of cytokines, sialidases, loads of G. vaginalis and total bacteria were assessed by ELISA, conversion of MUAN and quantitative real-time PCR, respectively. A principal component analysis(PCA) using all measured parameters was performed to compare the three different types of flora. Results showed that intermediate flora is associated with increased cervicovaginal IL-1beta in relation to normal flora(P<0.0001). When compared to bacterial vaginosis, intermediate flora has higher IL-8 and IL-10 levels(P<0.01). Sialidases were in significantly lower levels in normal and intermediate flora than bacterial vaginosis(P<0.0001). Loads of G. vaginalis and total bacterial differed among all groups(P<0.0001), being highest in bacterial vaginosis. PCA showed that normal and intermediate flora were closely scattered, while bacterial vaginosis were grouped separately.

CONCLUSION

Although intermediate flora shows some differences in cytokines, sialidases and bacterial loads in relation to normal flora and bacterial vaginosis, when taken together, general microbiological and immunological pattern pattern of intermediate flora resembles the normal flora.

Using an in-vitro biofilm model to assess the virulence potential of bacterial vaginosis or non-bacterial vaginosis Gardnerella vaginalis isolates

Gardnerella vaginalis is the most common species found in bacterial vaginosis (BV). However, it is also present in a significant proportion of healthy women and G. vaginalis vaginal colonization does not always lead to BV. In an effort to better understand the differences between G. vaginalis isolated from women with a positive (BV) versus a negative (non-BV) diagnosis of BV, we compared the virulence potential of 7 BV and 7 non-BV G. vaginalis isolates and assessed the virulence factors related to biofilm formation, namely: initial adhesion and cytotoxic effect, biofilm accumulation, susceptibility to antibiotics, and transcript levels of the known vaginolysin, and sialidase genes. Furthermore, we also determined the ability of G. vaginalis to displace lactobacilli previously adhered to HeLa cells. Our results showed that non-BV strains were less virulent than BV strains, as suggested by the lower cytotoxicity and initial adhesion to Hela cells. Significant differences in expression of known virulence genes were also detected, further suggesting a higher virulence potential of the BV associated G. vaginalis. Importantly, we demonstrated that BV associated G. vaginalis were able to displace pre-coated vaginal protective lactobacilli and we hypothesize this to be a trigger for BV development.

Influence of Biofilm Formation by Gardnerella vaginalis and Other Anaerobes on Bacterial Vaginosis

Bacterial vaginosis (BV) is the worldwide leading vaginal disorder among women of reproductive age. BV is characterized by the replacement of beneficial lactobacilli and the augmentation of anaerobic bacteria. Gardnerella vaginalis is a predominant bacterial species, but BV is also associated with other numerous anaerobes, such as Atopobium vaginae, Mobiluncus mulieris, Prevotella bivia, Fusobacterium nucleatum, and Peptoniphilus species. Currently, the role of G. vaginalis in the etiology of BV remains a matter of controversy. However, it is known that, in patients with BV, a biofilm is usually formed on the vaginal epithelium and that G. vaginalis is typically the predominant species. So, the current paradigm is that the establishment of a biofilm plays a key role in the pathogenesis of BV. This review provides background on the influence of biofilm formation by G. vaginalis and other anaerobes, from the time of their initial adhesion until biofilm formation, in the polymicrobial etiology of BV and discusses the commensal and synergic interactions established between them to understand the phenotypic shift of G. vaginalis biofilm formation to BV establishment.

Selecting anti-microbial treatment of aerobic vaginitis

Aerobic vaginitis (AV) is a vaginal infectious condition which is often confused with bacterial vaginosis (BV) or with the intermediate microflora as diagnosed by Nugent's method to detect BV on Gram-stained specimens. However, although both conditions reflect a state of lactobacillary disruption in the vagina, leading to an increase in pH, BV and AV differ profoundly. While BV is a noninflammatory condition composed of a multiplex array of different anaerobic bacteria in high quantities, AV is rather sparely populated by one or two enteric commensal flora bacteria, like Streptococcus agalactiae, Staphylocuccus aureus, or Escherichia coli. AV is typically marked by either an increased inflammatory response or by prominent signs of epithelial atrophy or both. The latter condition, if severe, is also called desquamative inflammatory vaginitis. As AV is per exclusionem diagnosed by wet mount microscopy, it is a mistake to treat just vaginal culture results. Vaginal cultures only serve as follow-up data in clinical research projects and are at most used in clinical practice to confirm the diagnosis or exclude Candida infection. AV requires treatment based on microscopy findings and a combined local treatment with any of the following which may yield the best results: antibiotic (infectious component), steroids (inflammatory component), and/or estrogen (atrophy component). In cases with Candida present on microscopy or culture, antifungals must be tried first in order to see if other treatment is still needed. Vaginal rinsing with povidone iodine can provide rapid relief of symptoms but does not provide long-term reduction of bacterial loads. Local antibiotics most suitable are preferably non-absorbed and broad spectrum, especially those covering enteric gram-positive and gram-negative aerobes, like kanamycin. To achieve rapid and short-term improvement of severe symptoms, oral therapy with amoxyclav or moxifloxacin can be used, especially in deep dermal vulvitis and colpitis infections with group B streptococci or (methicillin resistant) Staphylococcus aureus. Since the latter colonizations are frequent, but seldom inflammatory infections, we in general discourage the use of oral antibiotics in women with AV. In cases with a severe atrophy component (more than 10 % of epithelial cells are of the parabasal type), local estrogens can be used; and in postmenopausal or breast cancer patients with a contraindication for estrogens, even a combination of probiotics with an ultra-low dose of local estriol may be considered.

Metabolic signatures of bacterial vaginosis

Bacterial vaginosis (BV) is characterized by shifts in the vaginal microbiota from Lactobacillus dominant to a microbiota with diverse anaerobic bacteria. Few studies have linked specific metabolites with bacteria found in the human vagina. Here, we report dramatic differences in metabolite compositions and concentrations associated with BV using a global metabolomics approach. We further validated important metabolites using samples from a second cohort of women and a different platform to measure metabolites. In the primary study, we compared metabolite profiles in cervicovaginal lavage fluid from 40 women with BV and 20 women without BV. Vaginal bacterial representation was determined using broad-range PCR with pyrosequencing and concentrations of bacteria by quantitative PCR. We detected 279 named biochemicals; levels of 62% of metabolites were significantly different in women with BV. Unsupervised clustering of metabolites separated women with and without BV. Women with BV have metabolite profiles marked by lower concentrations of amino acids and dipeptides, concomitant with higher levels of amino acid catabolites and polyamines. Higher levels of the signaling eicosanoid 12-hydroxyeicosatetraenoic acid (12-HETE), a biomarker for inflammation, were noted in BV. Lactobacillus crispatus and Lactobacillus jensenii exhibited similar metabolite correlation patterns, which were distinct from correlation patterns exhibited by BV-associated bacteria. Several metabolites were significantly associated with clinical signs and symptoms (Amsel criteria) used to diagnose BV, and no metabolite was associated with all four clinical criteria. BV has strong metabolic signatures across multiple metabolic pathways, and these signatures are associated with the presence and concentrations of particular bacteria.

Bacterial vaginosis (BV) is a common but highly enigmatic condition that is associated with adverse outcomes for women and their neonates. Small molecule metabolites in the vagina may influence host physiology, affect microbial community composition, and impact risk of adverse health outcomes, but few studies have comprehensively studied the metabolomics profile of BV. Here, we used mass spectrometry to link specific metabolites with particular bacteria detected in the human vagina by PCR. BV was associated with strong metabolic signatures across multiple pathways affecting amino acid, carbohydrate, and lipid metabolism, highlighting the profound metabolic changes in BV. These signatures were associated with the presence and concentrations of particular vaginal bacteria, including some bacteria yet to be cultivated, thereby providing clues as to the microbial origin of many metabolites. Insights from this study provide opportunities for developing new diagnostic markers of BV and novel approaches for treatment or prevention of BV.

Contextualizing racial disparities in preterm delivery: a rhetorical analysis of U.S. epidemiological research at the turn of the 21st century

Preterm delivery (PTD), defined as delivery prior to 37 weeks gestation, is a key contributor to persistent racial disparities in infant mortality in the United States. Five major funding initiatives were devoted to advancing PTD epidemiology during the 1990s and 2000s. By examining content and rhetorical features of 94 studies conducted under these initiatives, and published between 1993 and 2011, this paper considers how calls for more "contextual" approaches (focusing on social and environmental contexts) interacted with more "conventional" approaches (focusing on individual-level risk factors) to PTD epidemiology during this period. Contextual advocates initially emphasized complex biosocial reasoning to better connect social adversity with embodied outcomes. Yet responses by researchers invested in conventional approaches, as well as in studies published under new initiatives that explicitly claimed to incorporate contextual insights, often reframed this complex reasoning in biologically reductionist terms. Subsequent contextual advocates then focused on developing statistical methods to support research about social and environmental causes of PTD, and this strategy appears to have gained some traction with conventional researchers. These findings call for closer attention to language and power in both social scientific studies of epidemiological knowledge production, as well as among epidemiologists themselves.

Genetic and biochemical diversity of Gardnerella vaginalis strains isolated from women with bacterial vaginosis

Gardnerella vaginalis is considered a substantial player in the progression of bacterial vaginosis (BV). We analysed 17 G. vaginalis strains isolated from the genital tract of women diagnosed with BV to establish a potential link between genotypes/biotypes and the expression of virulence factors, vaginolysin (VLY) and sialidase, which are assumed to play a substantial role in the pathogenesis of BV. Amplified ribosomal DNA restriction analysis revealed two G. vaginalis genotypes. Gardnerella vaginalis isolates of genotype 2 appeared more complex than genotype 1 and were subdivided into three subtypes. Biochemical typing allowed us to distinguish four different biotypes. A great diversity of the level of VLY production among the isolates of G. vaginalis may be related to a different cytotoxicity level of the strains. We did not find any correlation between VLY production level and G. vaginalis genotype/biotype. In contrast, a link between G. vaginalis genotype and sialidase production was established. Our findings on the diversity of VLY expression level in different clinical isolates and linking sialidase activity with the genotype of G. vaginalis could help to evaluate the pathogenic potential of different G. vaginalis strains.

High sialidase levels increase preterm birth risk among women who are bacterial vaginosis-positive in early gestation

OBJECTIVE

The purpose of this study was to assess whether vaginal sialidases level in early pregnancy is associated with preterm birth among women who are bacterial vaginosis-positive.

STUDY DESIGN

Of the 1806 women who were enrolled at < 20 weeks of gestation, 800 of the women were bacterial vaginosis-positive (Nugent score, 7-10); 707 of the women had birth outcome data; 109 of the women who were bacterial vaginosis-positive had an adverse preterm outcome, which included 53 spontaneous preterm births (19 births were early at 20-34 weeks, and 34 births were late at 34-37 weeks), and 14 of the women had late miscarriages (12-20 weeks). Sialidase levels were compared with 352 control subjects (term normal birthweight infants).

RESULTS

Sialidase levels at ≥ 5, ≥ 10, and ≥ 14 nmol (odds ratio [OR], 1.56; 95% confidence interval [CI], 1.01-2.41; OR, 2.14; 95% CI, 1.25-3.64; OR, 3.17; 95% CI, 1.64-6.10, respectively) was associated significantly with all adverse preterm outcomes. The ≥ 10 nmol and ≥ 14 nmol cut-points were associated strongly with early spontaneous preterm births (OR, 3.79; 95% CI, 1.42-10.10 and OR, 5.36; 95% CI, 1.77-16.23, respectively) and late miscarriages (OR, 4.87; 95% CI, 1.61-14.65; OR, 8.33; 95% CI, 2.57-26.9, respectively).

CONCLUSION

Elevated sialidase level that is measured at 12 weeks of gestation is associated strongly with early spontaneous preterm births and late miscarriage.

Antagonism and synergism in Gardnerella vaginalis strains isolated from women with bacterial vaginosis

Antagonistic and synergistic substances are important for interactions between micro-organisms associated with human body surfaces, either in healthy or in diseased conditions. In the present study, such compounds produced by Gardnerella vaginalis strains isolated from women with bacterial vaginosis (BV) were detected in vitro and the antagonistic ones were partially characterized. Among 11 G. vaginalis strains tested, all showed antagonistic activity against at least one of the 22 indicator bacteria assayed. Interestingly, for some of these strains, antagonism reverted to synergism, favouring one of the indicator strains (Peptostreptococcus anaerobius) when the growth medium was changed. Partial characterization of antagonistic substances suggested a bacteriocin-like chemical nature. Depending on growth conditions, G. vaginalis isolated from women with BV produced antagonistic or synergistic compounds for other bacterial components of the vaginal ecosystem. This is the first report to our knowledge of the production of antagonistic and/or synergistic substances by G. vaginalis. This ability may be a pivotal factor in understanding BV and the ecological role of this bacterium in the vaginal environment.

Among pregnant women with bacterial vaginosis, the hydrolytic enzymes sialidase and prolidase are positively associated with interleukin-1beta

OBJECTIVE

The objective of the study was to explore the mechanisms of local innate immunity induction and modulation in pregnant women with bacterial vaginosis (BV).

STUDY DESIGN

A total of 200 singleton pregnant women in early gestation (12 +/- 4 weeks) with BV (Nugent 7-10) without concurrent vaginal infections with Trichomonas vaginalis, Chlamydia trachomatis, Neisseria gonorrhoeae, syphilis, and yeast. Concentrations of vaginal interleukin (IL)-1beta and IL-8, the number of neutrophils, and the levels of sialidase and prolidase hydrolytic enzymes were determined in vaginal fluid.

RESULTS

Concentrations of vaginal IL-1beta had a strong positive correlation with levels of sialidase (P < .001) and prolidase (P < .001). Conversely, such enzymes were negatively correlated with the ratio of IL-8/IL-1beta (both P < .001) and were not significantly associated with concentrations of IL-8. Notably, the number of vaginal neutrophils had a negative correlation with sialidase (P = .007).

CONCLUSION

The strong induction of IL-1beta in BV-positive women appears to be associated with the production of the hydrolytic enzymes sialidase and prolidase by BV-associated bacteria. However, these 2 enzymes may inhibit the expected amplification of the proinflammatory IL-1beta cascade as evaluated by the down-regulation of the IL-8/IL-1beta ratio. A blunted response to IL-1beta signals may cause the poor rise of neutrophils, which is peculiar to BV. This impairment of local defense may contribute to increased susceptibility to adverse outcomes in BV-positive pregnant women.

Role of antibiotic therapy for bacterial vaginosis and intermediate flora in pregnancy

Bacterial vaginosis and intermediate flora are associated with late miscarriage and preterm delivery. The mechanisms involved are not yet fully understood. Clinical trials of antibiotic therapy to reduce these complications have yielded conflicting results. These trials, however, were conducted in mixed populations of pregnant women with variable risk profiles for preterm delivery. Furthermore, investigators used different criteria for diagnosis, treated with different antibiotics at different doses and via different routes, and initiated treatment at different gestational ages. Over 80% of pregnant women with abnormal vaginal flora have a good outcome, and in some populations the presence of bacterial vaginosis is not associated with preterm delivery, suggesting that other host factors may modify the risk. Recent studies have examined the roles of genetic regulation of host immune response, bacterial pathogenic factors, and enzymes in the vagina, and how these factors interact to drive a given outcome. These markers have the potential to better define the women at maximal risk and therefore guide future interventions. This chapter aims to appraise the current state of treatment of abnormal vaginal flora in pregnancy and suggest appropriate management based on the available evidence.

Modulation of vaginal immune response among pregnant women with bacterial vaginosis by Trichomonas vaginalis, Chlamydia trachomatis, Neisseria gonorrhoeae, and yeast

OBJECTIVE

This study was undertaken to examine the influence of coinfections on vaginal innate and adaptive immunity, and microbial enzyme activities of pregnant women with bacterial vaginosis (BV).

STUDY DESIGN

The population consisted of 265 singleton pregnant women in early gestation (<20 weeks) with BV (Nugent 7-10) who had vaginal fluid collected for measurement of interleukin-1beta (IL-1beta) and IL-8 concentrations, number of neutrophils, immunoglobulin A against Gardnerella vaginalis (anti-Gvh IgA), and activities of microbial sialidase and prolidase.

RESULTS

Among women with BV, median levels of vaginal IL-1beta (4-fold, P = .005), IL-8 (4-fold, P < .001), and neutrophils (6-fold, P = .013) were greatly increased in women with T vaginalis with respect to women without any coinfection. Yeast increased the level of IL-8 (5-fold, P < .001), but not IL-1beta (P = .239) and neutrophils (P = .060). Chlamydia trachomatis and Neisseria gonorrhoeae had no effect on vaginal cytokines. None of the coinfections influenced vaginal anti-Gvh IgA, sialidase and prolidase activities.

CONCLUSION

The strong proinflammatory cytokine induction by T. vaginalis may contribute to the observed increase in preterm birth among BV positive women coinfected with T. vaginalis treated with metronidazole.

Aetiology of preterm labour: bacterial vaginosis

Bacterial vaginosis (BV) is a common condition characterised by a polymicrobial disorder, with an overgrowth of several anaerobic or facultative bacteria and with a reduction or absence of lactobacillus colonisation. The prevalence of BV ranges from 4 to 64%, depending on the racial, geographic and clinical characteristics of the study population. In asymptomatic women, the prevalence varies from 12 to 25%, and similar percentages are observed in pregnant women. Although BV is associated with several adverse outcomes, such as upper genital tract infections, pelvic inflammatory disease, endometritis, preterm birth and low birthweight, many basic questions regarding the pathogenesis of BV remain unanswered. Mucosal immune system activation may represent a critical determinant of adverse consequences associated with BV. An unequal risk for BV acquisition and\or recurrence could derive from different mucosal immune host abilities and\or capability of invading microbes to produce factors that inactivate the local immune response. BV is associated with a two-fold increased risk of preterm birth, with the greatest risk when BV is present before 16 weeks of gestation (odds ratio = 7.55). This may indicate a critical period during early gestation when BV-related organisms can gain access to the upper genital tract and set the stage for spontaneous preterm labour later in gestation. The results of treatment trials for pregnant women with BV have been heterogeneous, with anywhere from an 80% reduction to a two-fold increase in preterm birth among women who received treatment. For this reason, in current clinical practice significant controversy surrounds determining not only who and when to screen but also who and how to treat. Recent evidence shows that individual genetic backgrounds can affect chemokine production. This is an interesting area for future research and could lead to trials of treatment only for women genetically predisposed to preterm birth.

Variation in vaginal immune parameters and microbial hydrolytic enzymes in bacterial vaginosis positive pregnant women with and without Mobiluncus species

OBJECTIVE

This study was undertaken to assess if levels of interleukin-1beta (IL-1beta), IL-8, sialidase, prolidase and immunoglobulin A against Gardenerella vaginalis hemolysin (anti-Gvh IgA) in vaginal secretions differ between BV+ women with (M+) and without (M-) Mobiluncus spp.

STUDY DESIGN

Vaginal secretions were obtained from 265 women at their first prenatal care visit and assessed for all study parameters. Gram stain evaluation using Nugent criteria was performed and coinfection with sexually transmitted infections determined. Differences between BV+/M+ and BV+/M- women were evaluated using the chi2 statistic or Mann-Whitney test.

RESULTS

Of the 265 BV+ women, 43% (n = 113) were M+ of which 97% (n = 110) had Nugent scores of 9 or 10 . BV+/M+ women had elevated levels of sialidase (median value: 4.11 nmol vs 1.91 nmol of converted substrate; P = .003) but no difference in prolidase, anti-Gvh IgA, IL-1beta, IL-8, levels were found between the two groups. BV+/M- women had significantly higher rates of coinfection with Trichomonas vaginalis.

CONCLUSION

BV+/M+ women have higher vaginal concentrations of sialidase and lower rates of T. vaginalis compared with BV+/M- women. Further research is needed to assess the association of this, and other, microbiologic profiles to risk of adverse pregnancy outcome.

What's new in bacterial vaginosis and trichomoniasis?

The use of biochemical profiles and new molecular microbiologic methodologies is transforming our understanding of BV. Most important is the recognition of different subgroups of women who have BV who are at variable risk of certain obstetric and gynecologic complications. New diagnostic tests may soon be available that will allow women to test self-obtained specimens. Treatment of BV has lagged, although innovative methods appear to be helpful in managing recurrent diseases.

Assessment of cervical antibody concentrations fails to enhance the value of cervical length as a predictor of preterm delivery

OBJECTIVE

The purpose of this study was to determine if cervical fluid antibody concentrations can enhance the value of cervical length in predicting risk of preterm delivery.

STUDY DESIGN

We obtained cervical fluid samples with preweighed cellulose wicks from a prospective cohort of women 23 to 32 weeks' gestation with signs and symptoms of preterm labor and intact membranes. Total immunoglobulin A and G (IgA and IgG) concentrations were determined by enzyme-linked immunosorbent assay. Bacterial vaginosis was diagnosed by Gram stain, and cervical length was measured with endovaginal ultrasound.

RESULTS

For subjects with term (n = 77) and preterm (n = 24) deliveries, median IgA and IgG concentrations were 736 vs 643 microg/mL (P = .33) and 1528 vs 1769 microg/mL (P = .85). For subjects with normal flora (n = 71), intermediate flora (n = 14), and bacterial vaginosis (n = 16), median IgA and IgG concentrations were 717, 624, and 774 microg/mL (P = .90) and 1383, 1553, and 2731 microg/mL (P = .02). In a forward stepwise logistic regression model, cervical length was the only factor associated with preterm delivery (P < .001).

CONCLUSION

Measuring the concentrations of IgA and IgG in cervical fluid does not enhance the value of cervical length in predicting risk of preterm delivery.

Combination of vaginal pH with vaginal sialidase and prolidase activities for prediction of low birth weight and preterm birth

OBJECTIVE

The purpose of this study was to assess if easy to measure vaginal fluid biomarkers are predictive for low birth weight (LBW, <2500 g), very LBW (VLBW, <1500 g), spontaneous preterm at <37 weeks' gestation, and total preterm deliveries (at <37, <35, <32 weeks' gestation).

STUDY DESIGN

Low and high cutoffs for vaginal fluid pH, sialidase, and prolidase activities were examined in a nested case-control study of 579 Danish women (from a study population of 2846 women) with samples collected at mean 17 weeks' gestation. One hundred sixteen LBW (17 VLBW), 117 preterm deliveries (85 spontaneous), and 418 normal term deliveries were analyzed.

RESULTS

Vaginal pH >/=4.7 or pH >/=5 by itself was not associated with LBW or prematurity. Conversely, combination of pH >/=5 and high sialidase activity demonstrated OR 17 (CI 1.8-150) for LBW; OR 31 (CI 1.8-516) for VLBW; along with OR 18 (CI 1.6-204) for preterm at <35 weeks'; and OR 31 (CI 1.9-542) for preterm at <32 weeks' gestation. The combination of pH >/=5 and high prolidase activity demonstrated OR 13 (CI 1.3-122) for LBW; OR 33 (CI 2.0-553) for VLBW, as well as OR 9.2 (CI 0.6-150) for preterm at <35 weeks'; and OR 35 (CI 2.0-586) for preterm at <32 weeks' gestation. In this population, no woman having high sialidase and high prolidase activity had a term birth, or a baby weighting >/=2500 g at birth.

CONCLUSION

In this Danish population, mid-gestation findings of vaginal fluid elevated pH with sialidase and/or prolidase were associated with LBW, VLBW, and early preterm at <35 or <32 weeks' gestation.

Vaginal Immunity in Bacterial Vaginosis

Vaginal immunity in response to microbial perturbation is still poorly understood and may be crucial for protection from adverse outcomes associated with bacterial vaginosis (BV). BV is the most prevalent vaginal disorder in adult women worldwide. However, its pathogenesis is still elusive. In BV-positive women, inflammatory signs are scant--approximately 50% of women are asymptomatic. The number of vaginal neutrophils in the BV-positive patient is not increased with respect to healthy women. In contrast, vaginal interleukin (IL)-1beta levels are largely increased. Recent findings indicate that microbial hydrolytic enzymes could be responsible for dampening the expected proinflammatory response cascade after IL-1beta increase. In other words, BV causes a large increase of vaginal IL-1beta, which is not paralleled by an increase of IL-8 levels, suggesting that BV-associated factors specifically dampen IL-8. The impairment of IL-8 increase may explain the absence of neutrophil increase in most women exposed to a massive abnormal anaerobic vaginal colonization (BV). Among BV-positive women, vaginal innate immunity is strongly correlated to a specific adaptive immune response: the immunoglobulin A (IgA) against the hemolysin produced by Gardnerella vaginalis (anti-Gvh IgA), which is the main bacterium present in BV. High anti-Gvh IgA levels are protective for adverse pregnancy outcomes. However, an exaggerated inflammatory response, mainly attributed to genetic polymorphisms, is also implicated in BV-associated adverse outcomes.

Nucleic acid-based diagnosis of bacterial vaginosis and improved management using probiotic lactobacilli

Bacterial vaginosis (BV) is a common condition in women that represents an imbalance of the vaginal microflora, lactobacilli depletion, and excess growth of mainly anaerobic Gram-negative pathogens. Diagnosis is made using a series of tests or a Gram stain of a vaginal smear. Treatment with antibiotics is quite effective, but recurrences are common. A study of 55 vaginal samples from 11 postmenopausal women showed the presence of BV by the Gram stain-based Nugent scoring system, and polymerase chain reaction-denaturing gradient gel electrophoresis showed that Bacteroides or Prevotella species were the most common isolates recovered (24 of 25), with Escherichia coli, Staphylococcus aureus, and Streptococcus agalactiae also found in some samples. In one case, only Gardnerella vaginalis was found. These findings illustrate that BV remains common even among otherwise healthy women, but it is not caused solely by either Gardnerella or Mobiluncus. Use of a FemExam system (Cooper Surgical, Shelton, CT), based upon elevated pH and trimethylamine levels, to screen vaginal smears from 59 healthy women showed poor correlation with the Gram stain method. A randomized, placebo-controlled trial of these subjects showed that the lactobacilli-dominant microbiota was restored in subjects with BV but not in controls, following 2 months of daily oral intake of Lactobacillus rhamnosus GR-1 and Lactobacillus fermentum RC-14. These studies show that nucleic acid-based methods are effective at identifying bacteria responsible for BV. If such methods could be used to develop a commercially available, self-use kit, women would be much better placed to take control of their own health, for example, using medicinal food or dietary supplement products such as the clinically proven probiotic strains L. rhamnosus GR-1 and L. fermentum RC-14.

The rationale for probiotics in female urogenital healthcare

Urogenital infections are a major reason that women visit their family physician and are referred to gastroenterology, gynecology, urology, and infectious disease specialists. The association between abnormal vaginal microbiota and increased risk for sexually transmitted infections, bladder and vaginal infections per se, and a higher rate of preterm labor indicate the need to better understand and manage urogenital health. The concept of probiotics arose from the realization that humans are inhabited with microbes from birth and that these organisms play a role in preventing disease. Defined as "live microorganisms, which when administered in adequate amounts confer a health benefit on the host," probiotic strains have already been shown to effectively prevent diarrhea and to hold potential in preventing and treating tonsillitis, caries, renal calculi, and respiratory infections. This review provides a rationale for the use of probiotics in maintaining female vaginal and bladder health and as a treatment option for recurrent bacterial vaginosis, urinary tract infection, yeast vaginitis, and sexually transmitted infections. We consider only probiotic strains that fulfill the United Nations/World Health Organization Guidelines for Probiotics in being fully characterized and clinically documented through scientific investigations describing known or presumed mechanisms of action. Although medical practitioners as yet are unable to access these probiotic strains, an awareness of recent and ongoing research for probiotics is important, as results are encouraging. The concept of probiotic therapy is familiar to many consumers and although it has historically lacked credibility in the medical community, perceptions are changing.

The potential for probiotics to prevent bacterial vaginosis and preterm labor

Infections of the urogenital tract in women represent a major burden on the quality of life of women and on the health care system of Canada and other countries. Complications arising from bacterial vaginosis (BV) include increased risk of sexually transmitted diseases including human immunodeficiency virus and elevated risk of preterm birth (PTB). Pharmaceutical interventions, such as antibiotics, have been suboptimally effective and have failed to reduce the incidence of PTB. The absence of lactobacilli in the vagina, a specific feature of BV, raises the question as to whether restoration of lactobacilli, by probiotic therapy, can restore the normal flora and improve the chances of having a healthy term pregnancy. The rationale for probiotic use in pregnant women is quite strong. Certain lactobacilli strains can safely colonize the vagina after oral and vaginal administration, displace and kill pathogens including Gardnerella vaginalis and Escherichia coli, and modulate the immune response to interfere with the inflammatory cascade that leads to PTB. Additional attributes of probiotics include their potential to degrade lipids and enhance cytokine levels, which promote embryo development. In a society that focuses on disease rather than health and drug therapy rather than natural preventive measures, it will take some effort to get remedies such as probiotics into mainstream care. Perhaps the escalating health care budgets and emergence of "superbugs" will provide the incentives to put in place clinical trials designed to evaluate how best to use the commensal organisms that, after all, make up more of our body than human cells, and without which none of us would survive.