Vaginal bacterial phaginosis?

Predicting Bacterial Vaginosis Development using Artificial Neural Networks

Bacterial vaginosis (BV) is a dysbiosis of the vaginal microbiome, characterized by the depletion of protective Lactobacillus spp. and overgrowth of anaerobes. Artificial neural network (ANN) modeling of vaginal microbial communities offers an opportunity for early detection of incident BV (iBV). 16S rRNA gene sequencing and quantitative PCR was performed on longitudinal vaginal specimens collected from participants within 14 days of iBV or from healthy participants to calculate the inferred absolute abundance (IAA) of vaginal bacterial taxa. ANNs were trained using the IAA of vaginal taxa from 420 vaginal specimens to classify individual vaginal specimens as either pre-iBV (collected before iBV onset) or Healthy. Feature importance was assessed to understand how specific vaginal micro-organisms contributed to model predictions. ANN modeling accurately classified >97% of specimens as either pre-iBV or Healthy (sensitivity >96%, specificity >98%) using IAA of 20 vaginal taxa. Model prediction accuracy was maintained when training models using only a few key vaginal taxa. Models trained using only the top five most important features achieved an accuracy of >97%, sensitivity >92%, and specificity >99%. Model predictive accuracy was further improved by training models on specimens from white and black participants separately; using only three feature models achieved an accuracy >96%, sensitivity >91%, and specificity >91%. Feature analysis found that Lactobacillus species L. gasseri and L. jensenii differed in how they contributed to model predictions in models trained with data stratified by race. A total of 420 vaginal specimens were analyzed, providing a robust dataset for model training and validation.

VIRGO2: Unveiling the Functional and Ecological Complexity of the Vaginal Microbiome with an Enhanced Non-Redundant Gene Catalog

Despite the importance of the cervicovaginal microbiome, the mechanisms that govern its composition and drive its impact on host physiology remain poorly understood. This study expands our understanding of the function and ecology of the vaginal microbiome using VIRGO2, an enhanced non-redundant gene catalog comprising over 1.7 million well-annotated genes from body-site specific microbes and viruses. Analyses using VIRGO2 revealed novel insights, including the identification of previously uncharacterized vaginal bacteria, features of the vaginal mycobiome and phageome, and differential expression of bacterial carbohydrate catabolic genes. Constructed from over 2,500 metagenomes and 4,000 bacterial genomes, VIRGO2 broadens geographic representation and microbial diversity compared to its predecessor. This updated catalog enables more precise profiling of taxonomic and functional composition from metagenomic and metatranscriptomic datasets. VIRGO2 is a critical resource for integrative analyses of vaginal microbial communities and their interactions with host tissues, thereby enhancing our mechanistic understanding of vaginal health and disease.

The Role of Prevotella Species in Female Genital Tract Infections

Female genital tract infections (FGTIs) include vaginal infections (e.g., bacterial vaginosis [BV]), endometritis, pelvic inflammatory disease [PID], and chorioamnionitis [amniotic fluid infection]. They commonly occur in women of reproductive age and are strongly associated with multiple adverse health outcomes including increased risk of HIV/sexually transmitted infection acquisition and transmission, infertility, and adverse birth outcomes such as preterm birth. These FGTIs are characterized by a disruption of the cervicovaginal microbiota which largely affects host immunity through the loss of protective, lactic acid-producing Lactobacillus spp. and the overgrowth of facultative and strict anaerobic bacteria. Prevotella species (spp.), anaerobic Gram-negative rods, are implicated in the pathogenesis of multiple bacterial FGTIs. Specifically, P. bivia, P. amnii, and P. timonensis have unique virulence factors in this setting, including resistance to antibiotics commonly used in treatment. Additionally, evidence suggests that the presence of Prevotella spp. in untreated BV cases can lead to infections of the upper female genital tract by ascension into the uterus. This narrative review aims to explore the most common Prevotella spp. in FGTIs, highlight their important role in the pathogenesis of FGTIs, and propose future research in this area.

Characterization of Vaginal Microbial Community Dynamics in the Pathogenesis of Incident Bacterial Vaginosis, a Pilot Study

BACKGROUND

Despite more than 60 years of research, the etiology of bacterial vaginosis (BV) remains controversial. In this pilot study, we used shotgun metagenomic sequencing to characterize vaginal microbial community changes before the development of incident BV (iBV).

METHODS

A cohort of African American women with a baseline healthy vaginal microbiome (no Amsel criteria, Nugent score 0-3 with no Gardnerella vaginalis morphotypes) were followed for 90 days with daily self-collected vaginal specimens for iBV (≥2 consecutive days of a Nugent score of 7-10). Shotgun metagenomic sequencing was performed on select vaginal specimens from 4 women, every other day for 12 days before iBV diagnosis. Sequencing data were analyzed through Kraken2 and bioBakery 3 workflows, and specimens were classified into community state types. Quantitative polymerase chain reaction was performed to compare the correlation of read counts with bacterial abundance.

RESULTS

Common BV-associated bacteria such as G. vaginalis , Prevotella bivia , and Fannyhessea vaginae were increasingly identified in the participants before iBV. Linear modeling indicated significant increases in G. vaginalis and F . vaginae relative abundance before iBV, whereas the relative abundance of Lactobacillus species declined over time. The Lactobacillus species decline correlated with the presence of Lactobacillus phages. We observed enrichment in bacterial adhesion factor genes on days before iBV. There were also significant correlations between bacterial read counts and abundances measured by quantitative polymerase chain reaction.

CONCLUSIONS

This pilot study characterizes vaginal community dynamics before iBV and identifies key bacterial taxa and mechanisms potentially involved in the pathogenesis of iBV.

The contribution of bacteriophages to the aetiology and treatment of the bacterial vaginosis syndrome

Bacteriophages are obligate intracellular viruses that parasitize bacteria, making use of the host biosynthetic machinery. Bacterial vaginosis (BV) causes serious adverse sequelae, such as sexually transmitted infections, seroconversion to HIV positivity, and preterm birth. The aetiology of BV is multifactorial, and the vaginal microbiota, the response to antibiotics, and the phenotypic outcomes differ between cases. The choice of antibiotics to treat BV depends on the clinician’s personal experience, which contributes to the poor outcome of BV treatment and high recurrence rate. In this review, we classify BV into two subtypes based on whether or not the BV case is sexually associated (potentially phage-related). An appropriate antibiotic can be selected on the basis of this BV-typing to optimise the short- and long-term effects of treatment. Not all Lactobacillus spp. are helpful or protective and some may sequestrate metronidazole, which mitigates its therapeutic efficacy. Phages, used therapeutically, could contribute to eubiosis by sparing beneficial species of Lactobacilli. However, Lactobacilli have an important role in maintaining vaginal eubiosis, so conventional wisdom has been that treatment of BV may benefit from metronidazole that conserves lactobacilli rather than clindamycin, which destroys lactobacilli. Furthermore, if the quality and quantity of vaginal lactobacilli are compromised by phage colonisation, as in the sexually transmitted subtype, eradication of lactobacilli with clindamycin followed by replacement by probiotics may be better therapeutically than metronidazole and reduce recurrence rates. Accordingly, the subtype of BV may provide a more scientific approach to antibiotic selection, which is absent in current clinical guidelines. We provide support for the role of bacteriophages in the aetiology, recurrence or failure to cure BV following treatment, through parasitic colonisation of lactobacilli that may be sexually transmitted and may be enhanced by other risk factors like smoking, a factor associated with BV.

The female reproductive tract virome: understanding the dynamic role of viruses in gynecological health and disease

The human body is inhabited by a large and complex network of commensal and predatory eukaryotic viruses and bacteriophages collectively termed the virome. Despite being the most abundant and genetically diverse biological entities on the planet, the impact of viruses on human health especially within the female reproductive tract (FRT) remains understudied. To better appreciate current knowledge regarding the dynamic role of viruses in FRT health and disease, in this review we highlight the known constituents of the FRT virome, transkingdom interactions within the FRT and their influence on gynecological disease. A better understanding of the FRT virome may pave the way toward improved outcomes in gynecological, reproductive, and neonatal health.

The Vaginal Microbiome: V. Therapeutic Modalities of Vaginal Microbiome Engineering and Research Challenges

OBJECTIVE

This series of articles, titled The Vaginal Microbiome (VMB), written on behalf of the International Society for the Study of Vulvovaginal Disease, aims to summarize the recent findings and understanding of the vaginal bacterial microbiota, mainly regarding areas relevant to clinicians specializing in vulvovaginal disorders.

MATERIALS AND METHODS

A search of PubMed database was performed, using the search terms "vaginal microbiome" with "treatment," "diagnosis," and "research." Full article texts were reviewed. Reference lists were screened for additional articles.

RESULTS

The currently available approaches for treating vaginitis or attempting to modulate the VMB are often insufficient. It has traditionally relied on the use of antibiotics, antiseptics, and antifungals. The fifth and last article of this series discusses the new and/or alternative therapeutic modalities. It addresses the role of probiotics, prebiotics and symbiotics, activated charcoal, biofilm disrupting agents, acidifying agents, phage therapy, and the concept of vaginal microbiome transplant. The challenges facing the research of VMB, including the clinical impact of microbiome manipulation, classification, and new diagnostic approaches are discussed.

CONCLUSIONS

Microbiome research has grown dramatically in recent years, motivated by innovations in technology and decrease in analysis costs. This research has yielded huge insight into the nature of microbial communities, their interactions, and effects with their hosts and other microbes. Further understanding of the bacterial, fungal, phage, and viral microbiomes in combination with host genetics, immunologic status, and environmental factors is needed to better understand and provide personalized medical diagnostics and interventions to improve women's health.

Presence and Persistence of Putative Lytic and Temperate Bacteriophages in Vaginal Metagenomes from South African Adolescents

The interaction between gut bacterial and viral microbiota is thought to be important in human health. While fluctuations in female genital tract (FGT) bacterial microbiota similarly determine sexual health, little is known about the presence, persistence, and function of vaginal bacteriophages. We conducted shotgun metagenome sequencing of cervicovaginal samples from South African adolescents collected longitudinally, who received no antibiotics. We annotated viral reads and circular bacteriophages, identified CRISPR loci and putative prophages, and assessed their diversity, persistence, and associations with bacterial microbiota composition. Siphoviridae was the most prevalent bacteriophage family, followed by Myoviridae, Podoviridae, Herelleviridae, and Inoviridae. Full-length siphoviruses targeting bacterial vaginosis (BV)-associated bacteria were identified, suggesting their presence in vivo. CRISPR loci and prophage-like elements were common, and genomic analysis suggested higher diversity among Gardnerella than Lactobacillus prophages. We found that some prophages were highly persistent within participants, and identical prophages were present in cervicovaginal secretions of multiple participants, suggesting that prophages, and thus bacterial strains, are shared between adolescents. The number of CRISPR loci and prophages were associated with vaginal microbiota stability and absence of BV. Our analysis suggests that (pro)phages are common in the FGT and vaginal bacteria and (pro)phages may interact.

The Vaginal Virome-Balancing Female Genital Tract Bacteriome, Mucosal Immunity, and Sexual and Reproductive Health Outcomes?

Besides bacteria, fungi, protists and archaea, the vaginal ecosystem also contains a range of prokaryote- and eukaryote-infecting viruses, which are collectively referred to as the "virome". Despite its well-described role in the gut and other environmental niches, the vaginal virome remains understudied. With a focus on sexual and reproductive health, we summarize the currently known components of the vaginal virome, its relationship with other constituents of the vaginal microbiota and its association with adverse health outcomes. While a range of eukaryote-infecting viruses has been described to be present in the female genital tract (FGT), few prokaryote-infecting viruses have been described. Literature suggests that various vaginal viruses interact with vaginal bacterial microbiota and host immunity and that any imbalance thereof may contribute to the risk of adverse reproductive health outcomes, including infertility and adverse birth outcomes. Current limitations of vaginal virome research include experimental and analytical constraints. Considering the vaginal virome may represent the missing link in our understanding of the relationship between FGT bacteria, mucosal immunity, and adverse sexual and reproductive health outcomes, future studies evaluating the vaginal microbiome and its population dynamics holistically will be important for understanding the role of the vaginal virome in balancing health and disease.

Introducing Lu-1, a Novel Lactobacillus jensenii Phage Abundant in the Urogenital Tract

Bacteriophages (phages) play a key role in shaping microbial communities, including those of the human body. Phages are abundant members of the urogenital tract, most often persisting through the lysogenic life cycle as prophages integrated within the genomes of their bacterial hosts. While numerous studies of the urogenital microbiota have focused on the most abundant bacterial member of this niche–Lactobacillus species–very little is known about Lactobacillus phages. Focusing on Lactobacillus jensenii strains from the urinary tract, we identified numerous prophages related to the previously characterized Lv-1 phage from a vaginal L. jensenii strain. Furthermore, we identified a new L. jensenii phage, Lu-1. Evidence suggests that both phages are abundant within the urogenital tract. CRISPR spacer sequences matching to Lv-1 and Lu-1 prophages were identified. While first detected in urinary isolates, the Lu-1 phage was also discovered in L. jensenii isolates from vaginal and perineal swabs, and both phages were found in metagenomic data sets. The prevalence of these phages in the isolates suggests that both phages are active members of the urogenital microbiota.

The genital tract and rectal microbiomes: their role in HIV susceptibility and prevention in women

INTRODUCTION

Young women in sub-Saharan Africa are disproportionately affected by HIV, accounting for 25% of all new infections in 2017. Several behavioural and biological factors are known to impact a young woman's vulnerability for acquiring HIV. One key, but lesser understood, biological factor impacting vulnerability is the vaginal microbiome. This review describes the vaginal microbiome and examines its alterations, its influence on HIV acquisition as well as the efficacy of HIV prevention technologies, the role of the rectal microbiome in HIV acquisition, advances in technologies to study the microbiome and some future research directions.

DISCUSSION

Although the composition of each woman's vaginal microbiome is unique, a microbiome dominated by Lactobacillus species is generally associated with a "healthy" vagina. Disturbances in the vaginal microbiota, characterized by a shift from a low-diversity, Lactobacillus-dominant state to a high-diversity non-Lactobacillus-dominant state, have been shown to be associated with a range of adverse reproductive health outcomes, including increasing the risk of genital inflammation and HIV acquisition. Gardnerella vaginalis and Prevotella bivia have been shown to contribute to both HIV risk and genital inflammation. In addition to impacting HIV risk, the composition of the vaginal microbiome affects the vaginal concentrations of some antiretroviral drugs, particularly those administered intravaginally, and thereby their efficacy as pre-exposure prophylaxis (PrEP) for HIV prevention. Although the role of rectal microbiota in HIV acquisition in women is less well understood, the composition of this compartment's microbiome, particularly the presence of species of bacteria from the Prevotellaceae family likely contribute to HIV acquisition. Advances in technologies have facilitated the study of the genital microbiome's structure and function. While next-generation sequencing advanced knowledge of the diversity and complexity of the vaginal microbiome, the emerging field of metaproteomics, which provides important information on vaginal bacterial community structure, diversity and function, is further shedding light on functionality of the vaginal microbiome and its relationship with bacterial vaginosis (BV), as well as antiretroviral PrEP efficacy.

CONCLUSIONS

A better understanding of the composition, structure and function of the microbiome is needed to identify opportunities to alter the vaginal microbiome and prevent BV and reduce the risk of HIV acquisition.

Continuous versus interrupted use of vaginal probiotics plus vaginal clindamycin cream for bacterial vaginosis: a randomized controlled study

Purpose: To compare between continuous and interrupted use of vaginal probiotic after vaginal clindamycin cream for treatment and prevention of recurrence of bacterial vaginosis.Methods: A double-blinded randomized controlled clinical trial, 273 women were randomly allocated to use clindamycin 2% vaginal cream 5 g at bedtime for 7 days followed after 1 week by continuous probiotics vaginal capsule once daily for 6 weeks (n = 129) or clindamycin 2% vaginal cream 5 g at bedtime for 7 days followed by one probiotic vaginal capsule twice a week for 6 weeks (n = 144). The initial evaluation was at 1 week after cessation of probiotics treatment to estimate the cure rates, the follow-up visits were at 1, 3, 6, and 9 months from the initial visit. The primary outcome of this study was cure rate; the secondary outcomes were the frequency of recurrence, the presence of vaginal discharge, pH > 4.5, positive whiff test and detection of clue cells.Results: At the initial visit there was no significant difference in cure rate between continuous probiotics group and interrupted probiotics group (87.4 versus 82.5%; p = .81). There was no significant difference between the two groups in the recurrence rate at one, three, six and 9 months follow up visits (p = .16, p = .42, p = .59, p = .66). There was no significant difference between both groups regarding vaginal discharge reduction, pH dropping, the presence of positive whiff test and detection of clue cells at one, three, six and 9 months follow up visits. Except at 9-month visits, the differences in vaginal discharge reduction and positive whiff test were statically significant.Conclusions: After initial treatment of bacterial vaginosis with vaginal clindamycin cream, the continuous use of vaginal probiotics is equally effective to short repetitive courses in terms of cure rates and prevention of relapse.

Metatranscriptome Analysis of the Vaginal Microbiota Reveals Potential Mechanisms for Protection against Metronidazole in Bacterial Vaginosis

Bacterial vaginosis is a serious issue for women in their reproductive years. Although it can usually be cured by antibiotics, the recurrence rate is very high, and some women do not respond to antibiotic therapy. The reasons for that are not known. Therefore, we undertook a study to detect the activity of the complete microbiota in the vaginal fluid of women who responded to antibiotic therapy and compared it to the activity of the microbiota in women who did not respond. We found that one of the most important pathogens in bacterial vaginosis, Gardnerella vaginalis, has activated genes that can repair the DNA damage caused by the antibiotic in those women that do not respond to therapy. Suppressing these genes might be a possibility to improve the antibiotic therapy of bacterial vaginosis.

Bacterial vaginosis (BV) is a prevalent multifactorial disease of women in their reproductive years characterized by a shift from the Lactobacillus species-dominated microbial community toward a taxonomically diverse anaerobic community. For unknown reasons, some women do not respond to therapy. In our recent clinical study, among 37 women diagnosed with BV, 31 were successfully treated with metronidazole, while 6 still had BV after treatment. To discover possible reasons for the lack of response in those patients, we performed a metatranscriptome analysis of their vaginal microbiota, comparing them to the patients who responded. Seven of 8 clustered regularly interspaced short palindromic repeat (CRISPR)-associated (Cas) genes of Gardnerella vaginalis were highly upregulated in nonresponding patients. Cas genes, in addition to protecting against phages, might be involved in DNA repair, thus mitigating the bactericidal effect of DNA-damaging agents such as metronidazole. In the second part of our study, we analyzed the vaginal metatranscriptomes of four patients over 3 months and showed high in vivo expression of genes for pore-forming toxins in L. iners and of genes encoding enzymes for the production of hydrogen peroxide and d-lactate in L. crispatus.

IMPORTANCE Bacterial vaginosis is a serious issue for women in their reproductive years. Although it can usually be cured by antibiotics, the recurrence rate is very high, and some women do not respond to antibiotic therapy. The reasons for that are not known. Therefore, we undertook a study to detect the activity of the complete microbiota in the vaginal fluid of women who responded to antibiotic therapy and compared it to the activity of the microbiota in women who did not respond. We found that one of the most important pathogens in bacterial vaginosis, Gardnerella vaginalis, has activated genes that can repair the DNA damage caused by the antibiotic in those women that do not respond to therapy. Suppressing these genes might be a possibility to improve the antibiotic therapy of bacterial vaginosis.

Sexually transmitted infections: challenges ahead

WHO estimated that nearly 1 million people become infected every day with any of four curable sexually transmitted infections (STIs): chlamydia, gonorrhoea, syphilis, and trichomoniasis. Despite their high global incidence, STIs remain a neglected area of research. In this Commission, we have prioritised five areas that represent particular challenges in STI treatment and control. Chlamydia remains the most commonly diagnosed bacterial STI in high-income countries despite widespread testing recommendations, sensitive and specific non-invasive testing techniques, and cheap effective therapy. We discuss the challenges for chlamydia control and evidence to support a shift from the current focus on infection-based screening to improved management of diagnosed cases and of chlamydial morbidity, such as pelvic inflammatory disease. The emergence and spread of antimicrobial resistance in Neisseria gonorrhoeae is globally recognised. We review current and potential future control and treatment strategies, with a focus on novel antimicrobials. Bacterial vaginosis is the most common vaginal disorder in women, but current treatments are associated with frequent recurrence. Recurrence after treatment might relate to evidence that suggests sexual transmission is integral to the pathogenesis of bacterial vaginosis, which has substantial implications for the development of effective management approaches. STIs disproportionately affect low-income and middle-income countries. We review strategies for case management, focusing on point-of-care tests that hold considerable potential for improving STI control. Lastly, STIs in men who have sex with men have increased since the late 1990s. We discuss the contribution of new biomedical HIV prevention strategies and risk compensation. Overall, this Commission aims to enhance the understanding of some of the key challenges facing the field of STIs, and outlines new approaches to improve the clinical management of STIs and public health.

Advances in the Prevention of Infection-Related Preterm Birth

Infection-related preterm birth (PTB) is more common at early gestational ages and is associated with major neonatal mortality and morbidity. Abnormal genital tract microflora in early pregnancy predicts late miscarriage and early PTB. Accordingly, it is logical to consider antibiotics as an intervention. Unfortunately, the conclusions of systematic reviews and meta-analyses (SR&MAs) carried out in an attempt to explain the confusion over the heterogeneity of individual studies are flawed by the fact that undue reliance was placed on studies which: (a) had a suboptimal choice of antibiotic (mainly metronidazole) or used antibiotics not recommended for the treatment of bacterial vaginosis (BV) or BV-related organisms; (b) used antibiotics too late in pregnancy to influence outcome (23–27 weeks); and (c) included women whose risk of PTB was not due to abnormal genital tract colonization and hence unlikely to respond to antibiotics. These risks included: (a) previous PTB of indeterminate etiology; (b) low weight/body mass index; or (c) detection of fetal fibronectin, ureaplasmas, Group B streptococcus or Trichomonas vaginalis). While individual studies have found benefit of antibiotic intervention for the prevention of PTB, in meta-analyses these effects have been negated by large methodologically flawed studies with negative results. As a result, many clinicians think that any antibiotic given at any time in pregnancy to any woman at risk of PTB will cause more harm than good. Recently, a more focused SR&MA has demonstrated that antibiotics active against BV-related organisms, used in women whose risk of PTB is due to abnormal microflora, and used early in pregnancy before irreversible inflammatory damage has occurred, can reduce the rate of PTB. This review presents those data, the background and attempts to explain the confusion using new information from culture-independent molecular-based techniques. It also gives guidance on the structure of putative future antibiotic intervention studies.

Transmission of Nonviral Sexually Transmitted Infections and Oral Sex

Introduction

Oral sex is usually considered a lower-risk sexual activity when compared with sex, but it is frequently the cause of sexually transmitted infections (STI). In particular, STI transferred through oral sex might have no visible symptoms, depending on the type of infection.

Aims

The aim of this study is to review the literature about the role of oral sex in the transmission of nonviral STI.

Main Outcome Measures

State-of-the-art information in the area of STI in relation to sexual function and self–care, this last important for development of STI prevention products such as vaginal microbicides. Sexual behaviors assessed focusing on receiving oral sex and giving oral sex.

Methods

A search of the main electronic databases including registers of clinical controlled trials was performed in addition to a hand search of the most relevant Journals. The following electronic databases were searched: PubMed, Embase, Google Scholar, literature review of research articles, and public health department Internet Web sites, for the period of 1945–2011. In addition to searching the Clinical Trials Registry at the US National Institutes of Health, we also used the meta Register of Controlled Trials and the Cochrane Central Register of Controlled Trials.

Results

STI affect the mucous membranes both directly and indirectly producing characteristic diagnostic signs and lesions. Daily dental clinical activity needs an appropriate knowledge of any kind of oral lesions-related STI. The reader is offered a practical approach with clinically relevant recommendations that may prove useful in his/her daily practice when dealing with STI.

Conclusions

These data provide a foundation for understanding diverse STI. We advise physicians to be receptive to discuss sexuality issues and provide patients with adequate therapy.

The aetiology of bacterial vaginosis

Bacterial vaginosis (BV) is the most common vaginal infection among women of childbearing age. This condition is notorious for causing severe complications related to the reproductive health of women. Five decades of intense research established many risk factors for acquisition of BV; however, because of the complexity of BV and lack of a reliable animal model for this condition, its exact aetiology remains elusive. In this manuscript, we use a historical perspective to critically review the development of major theories on the aetiology of BV, ultimately implicating BV-related pathogens, healthy vaginal microbiota, bacteriophages and the immune response of the host. None of these theories on their own can reliably explain the epidemiological data. Instead, BV is caused by a complex interaction of multiple factors, which include the numerous components of the vaginal microbial ecosystem and their human host. Many of these factors are yet to be characterized because a clear understanding of their relative contribution to the aetiology of BV is pivotal to the formulation of an effective treatment for and prophylaxis of this condition.

Ecological basis for rational phage therapy

Understanding the mutual interactions of bacterial and phage populations in the environment of a human or animal body is essential in any attempt to influence these complex processes, particularly for rational phage therapy. Current knowledge on the impact of naturally occurring bacteriophages on the populations of their host bacteria, and their role in the homeostasis maintenance of a macro host, is still sketchy. The existing data suggest that different mechanisms stabilize phage-bacteria coexistence in different animal species or different body sites. The defining set of parameters governing phage infection includes specific physical, chemical, and biological conditions, such as pH, nutrient densities, host prevalence, relation to mucosa and other surfaces, the presence of phage inhibiting substances, etc. Phage therapy is also an ecological process that always implies three components that form a complex pattern of interactions: populations of the pathogen, the bacteriophages used as antibacterial agents, and the macroorganism. We present a review of contemporary data on natural bacteriophages occuring in human- and animal-body associated microbial communities, and analyze ecological and physiological considerations that determine the success of phage therapy in mammals.

The bacteriophages in human- and animal body-associated microbial communities

Felix d'Herelle first demonstrated, about 90 years ago, the presence of bacteriophages in human and animal body microbiota. Our comprehension of the impact of naturally occurring bacteriophages on symbiotic bacteria, and of their role in general homeostasis of macro-organism, nevertheless remains quite fragmentary. Analysis of data in various human- and animal body-associated microbial systems on phage occurrence, diversity, host specificity and dynamics, as well as host occurrence, specificity and dynamics, suggests that mechanisms which stabilize phage-bacteria coexistence are not identical for either different species or different body sites. Regulation by phage infection instead probably depends on specific physical, chemical and biological conditions, e.g. pH, nutrient densities, host prevalence, relation to mucosa and other surfaces and presence of phage inhibiting substances. In some animal species intestinal bacteriophages thus appear to exert significant selective pressure over at least some resident bacterial populations, resulting in phages playing important roles in the self-regulation of these microbial systems while at the same time contributing to maintenance of bacterial diversity (i.e. 'killing the winner'). Emerging data additionally suggest that bacteriophage particles could play roles in regulating the immune reactions of the macro-organism. Alternatively, for many systems links between phages and community characteristics have not been established.

Probiotics: potential to prevent HIV and sexually transmitted infections in women

Women are at significant risk of human immunodeficiency virus (HIV) and sexually transmitted infection (STI) acquisition with the genital mucosa serving as the main portal of infection. Exogenously supplied lactobacillus used as a probiotic may prove a cost-effective, female-initiated method to prevent HIV and STI infection in women. A probiotic may act indirectly through treating and preventing recurrent bacterial vaginosis or directly by secreting endogenous (e.g., hydrogen peroxide) and exogenous substances that block HIV and STI transmission. This review summarizes the preclinical and clinical studies that have been conducted so far to test probiotic bacteria for these purposes. Although significant progress has been made in this field, more fundamental research is required to better understand vaginal ecology to maximize probiotic formulations. Once identified, a suitable product will require testing in a well-designed, randomized, placebo-controlled trial to measure its effectiveness in augmenting antibiotic treatment to prevent bacterial vaginosis. If results from such a trial demonstrate efficacy, future studies should be designed to determine whether a probiotic can significantly lower the risk for HIV and STIs in at-risk female populations.

Prevalence of bacterial vaginosis in lesbians and heterosexual women in a community setting

OBJECTIVES

High prevalence of bacterial vaginosis (BV) has been reported in lesbians but most studies were based in sexually transmitted infection clinic settings; therefore, we wished to determine the prevalence and risk factors of BV in lesbians and heterosexual women in a community setting in the UK.

METHODS

A cross-sectional study recruiting lesbian women volunteers from community groups, events, clubs and bars. Heterosexual women were recruited from a community family planning clinic. They self-swabbed to create a vaginal smear, which was Gram-stained and categorised as BV, intermediate or normal flora. They completed a questionnaire about age, ethnic group, smoking, genital hygiene practices and sexual history.

RESULTS

Of 189 heterosexuals and 171 lesbians recruited, 354 had gradeable flora. BV was identified in 43 (25.7%) lesbians and 27 (14.4%) heterosexuals (adjusted OR 2.45, 95% CI 1.25 to 4.82; p = 0.009). Concordance of vaginal flora within lesbian partnerships was significantly greater than expected (27/31 (87%) couples, kappa = 0.63; p<0.001). Smoking significantly increased the risk of BV regardless of sexuality (adjusted OR 2.65; p = 0.001) and showed substantial concordance in lesbian partnerships but less than for concordance of flora.

CONCLUSIONS

Women who identified as lesbians have a 2.5-fold increased likelihood of BV compared with heterosexual women. The prevalence is slightly lower than clinic-based studies and as volunteers were recruited in community settings, this figure may be more representative of lesbians who attend gay venues. Higher concordance of vaginal flora within lesbian partnerships may support the hypothesis of a sexually transmissible factor or reflect common risk factors such as smoking.

Life in the littoral zone: lactobacilli losing the plot

Recurrent bacterial vaginosis is a challenge for those affected by it, and their physicians. Our inability to prevent relapse after treatment, may be because of the flawed approach of using antibiotics to treat a condition that is an imbalance rather than an infection. The maintenance of a healthy lactobacillus population offers an approach to preventing relapse: the problem is how best to do this. Physiological approaches such as the use of hydrogen peroxide, lactic acid, and exogenous lactobacilli need to be explored further. The role of bacterial vaginosis as a risk factor for acquisition of HIV and other STIs is a further impetus to attempting to prevent bacterial vaginosis from recurring.

Bacteriophages in autoimmune disease and other inflammatory conditions

There are several autoimmune diseases and other inflammatory conditions where an infectious aetiology is suggested by the epidemiology, clinical course and pathological findings. Many candidate bacteria and viruses have been considered as potential aetiological agents but mostly without firm proof. Bacteriophages are viruses that infect bacteria and may be found wherever bacteria are located, but would not be detected unless specifically sought. They have not previously been considered to be pathogens. Bacteriophages are immunogenic and therefore could play a role in the pathogenesis of autoimmune and other inflammatory diseases by acting as antigens on epithelial surfaces, bound to antibody as immune complexes, through molecular mimicry or possibly as superantigens.

Preterm birth among African American and white women: a multilevel analysis of socioeconomic characteristics and cigarette smoking

STUDY OBJECTIVE

Research shows that neighbourhood socioeconomic factors are associated with preterm delivery. This study examined whether cigarette smoking and individual socioeconomic factors modify the effects of neighbourhood factors on preterm delivery.

DESIGN

Case-control study.

SETTING

Moffit Hospital in San Francisco, California.

PARTICIPANTS

417 African American and 1244 white women, including all preterm and a random selection of term deliveries 1980-1990, excluding non-singleton pregnancies, congenital anomolies, induced deliveries, and women transported for special care. US census data from 1980 and 1990 were used to characterise the women's neighbourhoods, defined as census tracts.

RESULTS

Cigarette smoking increased the risk of preterm delivery among both African American (OR=1.77, 95% confidence intervals (CI) (1.12 to 2.79)) and white women (OR=1.25, 95% CI (1.01 to 1.55)). However, cigarette smoking did not attenuate or modify the association of neighbourhood factors with preterm delivery. Among African American women, having public insurance modified the relation between neighbourhood unemployment and preterm delivery; among women without public insurance, the risk of preterm delivery was low in areas with low unemployment and high in areas with high unemployment, while among women with public insurance the risk of preterm delivery was highest at low levels of neighbourhood unemployment.

CONCLUSIONS

Cigarette smoking was associated with preterm delivery, especially among African Americans. Adverse neighbourhood conditions had an influence on preterm delivery beyond that of cigarette smoking. The effects of some neighbourhood characteristics were different depending on individual socioeconomic status. Examining socioeconomic and behavioural/biological risk factors together may increase understanding of the complex causes of preterm delivery.

Bacteriocin susceptibility of Gardnerella vaginalis and its relationship to biotype, genotype, and metronidazole susceptibility

OBJECTIVE

Our purpose was to investigate the bacteriocin susceptibility of Gardnerella vaginalis and its relationship to biotype, genotype, and resistance to metronidazole.

STUDY DESIGN

Bacteriocin susceptibility of 36 G vaginalis clinical isolates was tested against a vaginal strain of Lactobacillus acidophilus by a growth-inhibition method. The relationship to biotype, genotype, and resistance to metronidazole were analyzed by the chi2 test and Fisher exact test.

RESULTS

Eight G vaginalis strains (22%) were bacteriocin-resistant. Biotypes 5 and 7 were found to be the most frequent among these resistant strains. Eight (42%) of the 19 isolates classified as biotype 5, 6, or 7 were bacteriocin-resistant compared with none of the isolates that were classified as other biotypes (P <.01). Biotype 5 was found in higher prevalence among the isolates resistant to bacteriocin (62%) than among the susceptible isolates (14%) (P =.01). Genotype B was found more frequently among the bacteriocin-resistant strains, but this finding was not statistically significant (P =.71). Seven (88%) bacteriocin-resistant strains were also resistant to metronidazole.

CONCLUSION

An association between biotype and an increased resistance to bacteriocin was found. The ability of G vaginalis to resist the antibacterial activity of Lactobacillus bacteriocin may be a pivotal factor in understanding bacterial vaginosis.

Can bacterial interference prevent infection?

The concept that one bacterial species can interfere with the ability of another to colonize and infect the host has at its foundation the prerequisite that bacteria must attach to biological surfaces to cause infection. Although this is an over-simplification of pathogenesis, it has led to studies aimed at creating vaccines that block adhesion events. Arguably, the use of commensal bacteria (also referred to as "normal flora", "indigenous" or "autochthonous" microorganisms) to inhibit pathogens has even greater potential than vaccine use, because these bacteria are natural competitors of pathogens and their action does not require host immune stimulation. Exogenous application of commensal organisms (probiotics) has been shown to reduce the risk of infections in the gut, urogenital tract and wound sites. To manipulate and optimize these effects, further studies are required to understand cell signaling amongst commensals and pathogens within biofilms adherent to host tissues. The potential for new therapeutic regimens using probiotics is significant and worthy of further study.

Recurrent Bacterial Vaginosis

Bacterial vaginosis (BV) is a common cause of vaginal discharge in women of childbearing age. In some individuals, it recurs frequently after treatment, frustrating both the patient and the physician. Standard BV treatment--metronidazole or clindamycin, administered either intravaginally or orally--is followed by relapse in approximately 30% of cases, within one month. Our inability to prevent relapse reflects our lack of understanding of how BV originates. BV has been associated with infectious morbidity in obstetrics and gynecology. Recent studies have found it to be a risk factor for HIV spread. These findings increase the need for us to be able to control recurrent BV and reduce its prevalence in the general population.