State of the Art for Diagnosis of Bacterial Vaginosis.

Bacterial vaginosis (BV) is the most common cause of vaginal discharge among reproductive-age women. It is associated with multiple adverse health outcomes, including increased risk of acquisition of HIV and other sexually transmitted infections (STIs), in addition to adverse birth outcomes. While it is known that BV is a vaginal dysbiosis characterized by a shift in the vaginal microbiota from protective Lactobacillus species to an increase in facultative and strict anaerobic bacteria, its exact etiology remains unknown. The purpose of this minireview is to provide an updated overview of the range of tests currently used for the diagnosis of BV in both clinical and research settings. This article is divided into two primary sections: traditional BV diagnostics and molecular diagnostics. Molecular diagnostic assays, particularly 16S rRNA gene sequencing, shotgun metagenomic sequencing, and fluorescence in situ hybridization (FISH), are specifically highlighted, in addition to multiplex nucleic acid amplification tests (NAATs), given their increasing use in clinical practice (NAATs) and research studies (16S rRNA gene sequencing, shotgun metagenomic sequencing, and FISH) regarding the vaginal microbiota and BV pathogenesis. We also provide a discussion of the strengths and weaknesses of current BV diagnostic tests and discuss future challenges in this field of research.

In vitro interactions within a biofilm containing three species found in bacterial vaginosis (BV) support the higher antimicrobial tolerance associated with BV recurrence.

BACKGROUND: Bacterial vaginosis (BV), the most common cause of vaginal discharge, is characterized by the presence of a polymicrobial biofilm on the vaginal epithelium, formed primarily by Gardnerella spp., but also other anaerobic species. Interactions between bacteria in multi-species biofilms are likely to contribute to increased virulence and to enhanced antimicrobial tolerance observed in vivo. However, functional studies addressing this question are lacking. OBJECTIVES: To gain insights into the role that interactions between BV-associated species in multi-species BV biofilms might have on antimicrobial tolerance, single- and triple-species biofilms formed by Gardnerella vaginalis, Fannyhessea (Atopobium) vaginae and Peptostreptococcus anaerobius were characterized, before and after metronidazole or clindamycin treatment. METHODS: Total biofilm biomass, total cells and cfu counts prior to and after antibiotic treatment were first determined. In addition, bacterial populations in the triple-species biofilms were also quantified by quantitative PCR (qPCR) and peptide nucleic acid (PNA) fluorescence in situ hybridization (FISH). RESULTS: Despite the effect observed in single-species biofilms, neither metronidazole nor clindamycin was effective in reducing triple-species biofilm biomass. Similar results were obtained when evaluating the number of total or culturable cells. Interestingly, despite differences between strain susceptibilities to antibiotics, the composition of the triple-species biofilms was not strongly affected by antibiotics. CONCLUSIONS: Taken together, these results strengthen the idea that, when co-incubated, bacteria can interact synergistically, leading to increased tolerance to antimicrobial therapy, which helps explain the observed clinically high BV recurrence rates.

Gardnerella Vaginalis Dominates Multi-Species Biofilms in both Pre-Conditioned and Competitive In Vitro Biofilm Formation Models.

Bacterial vaginosis (BV) is one of the most common bacterial vaginal infections worldwide. Despite its high prevalence, BV etiology is still unknown. Nevertheless, a hallmark of BV is the presence of a highly structured polymicrobial biofilm on the vaginal epithelium, formed primarily by Gardnerella spp. and other anaerobic species, of which co-colonization with Fannyhessea vaginae is considered an important diagnostic marker. We previously developed an in vitro biofilm model wherein Gardnerella was first allowed to establish an early biofilm that served as a scaffold for other species to adhere to. To better understand ecological interactions between BV-associated bacteria, we compared triple-species biofilms formed using two distinct models: a pre-conditioned (wherein Gardnerella vaginalis formed the early biofilm) model and a competitive (wherein all three bacteria were co-incubated together) model. Interestingly, synergistic growth interactions were more significant in the competitive model. Furthermore, the biofilm structure and species-specific distribution, as assessed by confocal laser scanning microscopy and using peptide nucleic acid fluorescence in situ hybridization method, revealed two very different triple-species morphotypes, suggesting that different interactions occur in the different models. Interestingly, independent of the model or triple-species consortium tested, we observed that G. vaginalis represented most of the biofilm bacterial composition, further highlighting the relevance of this taxon in BV.

DNA extraction leads to bias in bacterial quantification by qPCR.

Quantitative PCR (qPCR) has become a widely used technique for bacterial quantification. The affordability, ease of experimental design, reproducibility, and robustness of qPCR experiments contribute to its success. The establishment of guidelines for minimum information for publication of qPCR experiments, now more than 10 years ago, aimed to mitigate the publication of contradictory data. Unfortunately, there are still a significant number of recent research articles that do not consider the main pitfalls of qPCR for quantification of biological samples, which undoubtedly leads to biased experimental conclusions. qPCR experiments have two main issues that need to be properly tackled: those related to the extraction and purification of genomic DNA and those related to the thermal amplification process. This mini-review provides an updated literature survey that critically analyzes the following key aspects of bacterial quantification by qPCR: (i) the normalization of qPCR results by using exogenous controls, (ii) the construction of adequate calibration curves, and (iii) the determination of qPCR reaction efficiency. It is primarily focused on original papers published last year, where qPCR was applied to quantify bacterial species in different types of biological samples, including multi-species biofilms, human fluids, and water and soil samples. KEY POINTS: • qPCR is a widely used technique used for absolute bacterial quantification. • Recently published papers lack proper qPCR methodologies. • Not including proper qPCR controls significantly affect experimental conclusions.

Viable but non-cultivable state: a strategy for Staphylococcus aureus survivable in dual-species biofilms with Pseudomonas aeruginosa?

Pseudomonas aeruginosa and Staphylococcus aureus are two of the most prevalent respiratory pathogens in cystic fibrosis patients. Both organisms often cause chronic and recalcitrant infections, in large part due to their ability to form biofilms, being these mixed-species infections correlated with poor clinical outcomes. In this study, the hypothesis that S. aureus adopts phenotypes allowing its coexistence with P. aeruginosa during biofilm growth was put forward. We noticed that S. aureus undergoes a viable but non-cultivable (VBNC) state in the dominated P. aeruginosa dual-species consortia, whatsoever the strains used to form the biofilms. Moreover, an increased expression of genes associated with S. aureus virulence was detected suggesting that the phenotypic switching to VBNC state might account for S. aureus pathogenicity and, in turn, influence the clinical outcome of the mixed-species infection. Thus, P. aeruginosa seems to induce both phenotypic and transcriptomic changes in S. aureus, helping its survival and coexistence in the dual-species biofilms. Overall, our findings illustrate how interspecies interactions can modulate bacterial virulence in vitro, contributing to a better understanding of the behaviour of P. aeruginosa-S. aureus dual-species biofilms.

An Updated Conceptual Model on the Pathogenesis of Bacterial Vaginosis.

Bacterial vaginosis (BV) is the most common cause of vaginal discharge. It is associated with an increased risk of preterm delivery, pelvic inflammatory disease, and an increased risk of acquisition of sexually transmitted infections including human immunodeficiency virus (HIV). The epidemiology of BV supports sexual transmission. However, its etiology remains unknown. At the center of the debate is whether BV is caused by a primary pathogen or a polymicrobial consortium of microorganisms that are sexually transmitted. We previously published a conceptual model hypothesizing that BV is initiated by sexual transmission of Gardnerella vaginalis. Critics of this model have iterated that G. vaginalis is found in virginal women and in sexually active women with a normal vaginal microbiota. In addition, colonization does not always lead to BV. However, recent advances in BV pathogenesis research have determined the existence of 13 different species within the genus Gardnerella. It may be that healthy women are colonized by nonpathogenic Gardnerella species, whereas virulent strains are involved in BV development. Based on our results from a recent prospective study, in addition to an extensive literature review, we present an updated conceptual model for the pathogenesis of BV that centers on the roles of virulent strains of G. vaginalis, as well as Prevotella bivia and Atopobium vaginae.

Lactobacillus crispatus represses vaginolysin expression by BV associated Gardnerella vaginalis and reduces cell cytotoxicity.

Using a chemically-defined medium simulating genital tract secretions, we have shown that pre-adhering Lactobacillus crispatus to Hela epithelial cells reduced cytotoxicity caused by Gardnerella vaginalis. This effect was associated to the expression of vaginolysin and was specific to L. crispatus interference, as other vaginal facultative anaerobes had no protective effect.

Staphylococcus epidermidis is largely dependent on iron availability to form biofilms.

Staphylococcus epidermidis has long been known as a major bacterial coloniser of the human skin, yet it is also a prominent nosocomial pathogen. Its remarkable ability to assemble structured biofilms has been its major known pathogenic feature to date. Notwithstanding important discoveries that have been accomplished, several questions about S. epidermidis biofilm formation still remain to be elucidated. This study aimed to assess whether iron availability modulates S. epidermidis biofilm formation and, if so, to explore how such modulation occurs. Biofilms of three S. epidermidis strains were grown under iron-enriched/-deficient conditions and several physiologic and transcriptomic changes were assessed. Our data revealed that while physiologic iron levels do not compromise biofilm formation, iron excess or deficiency is detrimental for this process. Conversely, biofilm cells were not affected in the same way when grown planktonically. By studying biofilm cells in detail we found that their viability and cultivability were seriously compromised by iron deficiency. Also, a temporal analysis of biofilm formation revealed that iron excess/deficiency: i) impaired biomass accumulation from 6h onwards, and ii) induced changes in the biofilm structure, indicating that iron availability plays a pivotal role from an early biofilm development stage. The expression of several putative iron-related genes, namely encoding siderophore biosynthesis/transport-related proteins, was found to be modulated by iron availability, providing a biological validation of their function on S. epidermidis iron metabolism. This study therefore provides evidence that iron plays a pivotal role on S. epidermidis biofilm formation.

Critical review on biofilm methods.

Biofilms are widespread in nature and constitute an important strategy implemented by microorganisms to survive in sometimes harsh environmental conditions. They can be beneficial or have a negative impact particularly when formed in industrial settings or on medical devices. As such, research into the formation and elimination of biofilms is important for many disciplines. Several new methodologies have been recently developed for, or adapted to, biofilm studies that have contributed to deeper knowledge on biofilm physiology, structure and composition. In this review, traditional and cutting-edge methods to study biofilm biomass, viability, structure, composition and physiology are addressed. Moreover, as there is a lack of consensus among the diversity of techniques used to grow and study biofilms. This review intends to remedy this, by giving a critical perspective, highlighting the advantages and limitations of several methods. Accordingly, this review aims at helping scientists in finding the most appropriate and up-to-date methods to study their biofilms.

Poly-N-Acetylglucosamine Production by Staphylococcus epidermidis Cells Increases Their In Vivo Proinflammatory Effect.

Poly-N-acetylglucosamine (PNAG) is a major component of the Staphylococcus epidermidis biofilm extracellular matrix. However, it is not yet clear how this polysaccharide impacts the host immune response and infection-associated pathology. Faster neutrophil recruitment and bacterial clearance were observed in mice challenged intraperitoneally with S. epidermidis biofilm cells of the PNAG-producing 9142 strain than in mice similarly challenged with the isogenic PNAG-defective M10 mutant. Moreover, intraperitoneal priming with 9142 cells exacerbated liver inflammatory pathology induced by a subsequent intravenous S. epidermidis challenge, compared to priming with M10 cells. The 9142-primed mice had elevated splenic CD4(+) T cells producing gamma interferon and interleukin-17A, indicating that PNAG promoted cell-mediated immunity. Curiously, despite having more marked liver tissue pathology, 9142-primed mice also had splenic T regulatory cells with greater suppressive activity than those of their M10-primed counterparts. By showing that PNAG production by S. epidermidis biofilm cells exacerbates host inflammatory pathology, these results together suggest that this polysaccharide contributes to the clinical features associated with biofilm-derived infections.

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.

Immunoreactive pattern of Staphylococcus epidermidis biofilm against human whole saliva.

Saliva is essential to interact with microorganisms in the oral cavity. Therefore, the interest in saliva antimicrobial properties is on the rise. Here, we used an immunoproteomic approach, based on protein separation of Staphylococcus epidermidis biofilms by 2DE, followed by Western-blotting, to compare human serum and saliva reactivity profile. A total of 17 proteins were identified by MALDI-TOF/TOF. Serum and saliva presented a distinct pattern of immunoreactive proteins. Our results suggest that saliva seems to have higher propensity to react against S. epidermidis proteins with oxidoreductase activity and proteins involved with L-serine metabolic processes. We show that saliva was a powerful tool for the identification of potential S. epidermidis biofilms proteins.

Proteomic profile of dormancy within Staphylococcus epidermidis biofilms using iTRAQ and label-free strategies.

Staphylococcus epidermidis is an important nosocomial bacterium among carriers of indwelling medical devices, since it has a strong ability to form biofilms. The presence of dormant bacteria within a biofilm is one of the factors that contribute to biofilm antibiotic tolerance and immune evasion. Here, we provide a detailed characterization of the quantitative proteomic profile of S. epidermidis biofilms with different proportions of dormant bacteria. A total of 427 and 409 proteins were identified by label-free and label-based quantitative methodologies, respectively. From these, 29 proteins were found to be differentially expressed between S. epidermidis biofilms with prevented and induced dormancy. Proteins overexpressed in S. epidermidis with prevented dormancy were associated with ribosome synthesis pathway, which reflects the metabolic state of dormant bacteria. In the opposite, underexpressed proteins were related to catalytic activity and ion binding, with involvement in purine, arginine, and proline metabolism. Additionally, GTPase activity seems to be enhanced in S. epidermidis biofilm with induced dormancy. The role of magnesium in dormancy modulation was further investigated with bioinformatics tool based in predicted interactions. The main molecular function of proteins, which strongly interact with magnesium, was nucleic acid binding. Different proteomic strategies allowed to obtain similar results and evidenced that prevented dormancy led to an expression of a markedly different repertoire of proteins in comparison to the one of dormant biofilms.

Proteome signatures--how are they obtained and what do they teach us?

The dawn of a new Proteomics era, just over a decade ago, allowed for large-scale protein profiling studies that have been applied in the identification of distinctive molecular cell signatures. Proteomics provides a powerful approach for identifying and studying these multiple molecular markers in a vast array of biological systems, whether focusing on basic biological research, diagnosis, therapeutics, or systems biology. This is a continuously expanding field that relies on the combination of different methodologies and current advances, both technological and analytical, which have led to an explosion of protein signatures and biomarker candidates. But how are these biological markers obtained? And, most importantly, what can we learn from them? Herein, we briefly overview the currently available approaches for obtaining relevant information at the proteome level, while noting the current and future roles of both traditional and modern proteomics. Moreover, we provide some considerations on how the development of powerful and robust bioinformatics tools will greatly benefit high-throughput proteomics. Such strategies are of the utmost importance in the rapidly emerging field of immunoproteomics, which may play a key role in the identification of antigens with diagnostic and/or therapeutic potential and in the development of new vaccines. Finally, we consider the present limitations in the discovery of new signatures and biomarkers and speculate on how such hurdles may be overcome, while also offering a prospect for the next few years in what could be one of the most significant strategies in translational medicine research.

BV and non-BV associated Gardnerella vaginalis establish similar synergistic interactions with other BV-associated microorganisms in dual-species biofilms.

Dual-species biofilm formation between Gardnerella vaginalis strains isolated from women with or without bacterial vaginosis (BV) and other 24 BV-associated microorganisms support that the key difference in virulence potential between BV-negative and BV-positive G. vaginalis strains seems not to be related with biofilm maturation.

Gardnerella vaginalis outcompetes 29 other bacterial species isolated from patients with bacterial vaginosis, using in an in vitro biofilm formation model.

Despite the worldwide prevalence of bacterial vaginosis (BV), its etiology is still unknown. Although BV has been associated with the presence of biofilm, the ability of BV-associated bacteria to form biofilms is still largely unknown. Here, we isolated 30 BV-associated species and characterized their virulence, using an in vitro biofilm formation model. Our data suggests that Gardnerella vaginalis had the highest virulence potential, as defined by higher initial adhesion and cytotoxicity of epithelial cells, as well as the greater propensity to form a biofilm. Interestingly, we also demonstrated that most of the BV-associated bacteria had a tendency to grow as biofilms.

Comparative genomics of Lactobacillus crispatus suggests novel mechanisms for the competitive exclusion of Gardnerella vaginalis.

BACKGROUND: Lactobacillus crispatus is a ubiquitous micro-organism encountered in a wide range of host-associated habitats. It can be recovered from the gastrointestinal tract of animals and it is a common constituent of the vaginal microbiota of humans. Moreover, L. crispatus can contribute to the urogenital health of the host through competitive exclusion and the production of antimicrobial agents. In order to investigate the genetic diversity of this important urogenital species, we performed a comparative genomic analysis of L. crispatus. RESULTS: Utilizing the completed genome sequence of a strain ST1 and the draft genome sequences of nine other L. crispatus isolates, we defined the scale and scope of the pan- and core genomic potential of L. crispatus. Our comparative analysis identified 1,224 and 2,705 ortholog groups present in all or only some of the ten strains, respectively. Based on mathematical modeling, sequencing of additional L. crispatus isolates would result in the identification of new genes and functions, whereas the conserved core of the ten strains was a good representation of the final L. crispatus core genome, estimated to level at about 1,116 ortholog groups. Importantly, the current core was observed to encode bacterial components potentially promoting urogenital health. Using antibody fragments specific for one of the conserved L. crispatus adhesins, we demonstrated that the L. crispatus core proteins have a potential to reduce the ability of Gardnerella vaginalis to adhere to epithelial cells. These findings thereby suggest that L. crispatus core proteins could protect the vagina from G. vaginalis and bacterial vaginosis. CONCLUSIONS: Our pan-genome analysis provides insights into the intraspecific genome variability and the collective molecular mechanisms of the species L. crispatus. Using this approach, we described the differences and similarities between the genomes and identified features likely to be important for urogenital health. Notably, the conserved genetic backbone of L. crispatus accounted for close to 60% of the ortholog groups of an average L. crispatus strain and included factors for the competitive exclusion of G. vaginalis, providing an explanation on how this urogenital species could improve vaginal health.

Isolation and characterization of a new Staphylococcus epidermidis broad-spectrum bacteriophage.

Staphylococcus epidermidis is considered an important nosocomial pathogen, being very tolerant to the host immune system and antibiotherapy, particularly when in biofilms. Due to its high resistance, alternative antimicrobial strategies are under development. The use of bacteriophages is seen as an important strategy to combat pathogenic organisms. In this study, a S. epidermidis myovirus, SEP1, was isolated and characterized. The genome of this phage was sequenced and shown to be related peripherally to the genus Twortlikevirus. However, when compared with other phages of this genus, it showed DNA sequence identities no greater than 58.2 %. As opposed to other polyvalent viruses of the genus Twortlikevirus, SEP1 is highly specific to S. epidermidis strains. The good infectivity shown by this phage as well as its high lytic spectrum suggested that it might be a good candidate for therapeutic studies.