Extra-vaginal Bacterial Colonization and Risk for Incident Bacterial Vaginosis in a Population of Women who Have Sex with Men

Impact of Data and Study Characteristics on Microbiome Volatility Estimates

The human microbiome is a dynamic community of bacteria, viruses, fungi, and other microorganisms. Both the composition of the microbiome (the microbes that are present and their relative abundances) and the temporal variability of the microbiome (the magnitude of changes in their composition across time, called volatility) has been associated with human health. However, the effect of unbalanced sampling intervals and differential read depth on the estimates of microbiome volatility has not been thoroughly assessed. Using four publicly available gut and vaginal microbiome time series, we subsampled the datasets to several sampling intervals and read depths and then compared additive, multiplicative, centered log ratio (CLR)-based, qualitative, and distance-based measures of microbiome volatility between the conditions. We find that longer sampling intervals are associated with larger quantitative measures of change (particularly for common taxa), but not with qualitative measures of change or distance-based volatility quantification. A lower sequencing read depth is associated with smaller multiplicative, CLR-based, and qualitative measures of change (particularly for less common taxa). Strategic subsampling may serve as a useful sensitivity analysis in unbalanced longitudinal studies investigating clinical associations with microbiome volatility.

Vaginal bacterium Prevotella timonensis turns protective Langerhans cells into HIV-1 reservoirs for virus dissemination

Dysbiosis of vaginal microbiota is associated with increased HIV-1 acquisition, but the underlying cellular mechanisms remain unclear. Vaginal Langerhans cells (LCs) protect against mucosal HIV-1 infection via autophagy-mediated degradation of HIV-1. As LCs are in continuous contact with bacterial members of the vaginal microbiome, we investigated the impact of commensal and dysbiosis-associated vaginal (an)aerobic bacterial species on the antiviral function of LCs. Most of the tested bacteria did not affect the HIV-1 restrictive function of LCs. However, Prevotella timonensis induced a vast uptake of HIV-1 by vaginal LCs. Internalized virus remained infectious for days and uptake was unaffected by antiretroviral drugs. P. timonensis-exposed LCs efficiently transmitted HIV-1 to target cells both in vitro and ex vivo. Additionally, P. timonensis exposure enhanced uptake and transmission of the HIV-1 variants that establish infection after sexual transmission, the so-called Transmitted Founder variants. Our findings, therefore, suggest that P. timonensis might set the stage for enhanced HIV-1 susceptibility during vaginal dysbiosis and advocate targeted treatment of P. timonensis during bacterial vaginosis to limit HIV-1 infection.

Protease activities of vaginal Porphyromonas species disrupt coagulation and extracellular matrix in the cervicovaginal niche

Porphyromonas asaccharolytica and Porphyromonas uenonis are common inhabitants of the vaginal microbiome, but their presence has been linked to adverse health outcomes for women, including bacterial vaginosis and preterm birth. However, little is known about the pathogenesis mechanisms of these bacteria. The related oral opportunistic pathogen, Porphyromonas gingivalis, is comparatively well-studied and known to secrete numerous extracellular matrix-targeting proteases. Among these are the gingipain family of cysteine proteases that drive periodontal disease progression and hematogenic transmission to the placenta. In this study, we demonstrate that vaginal Porphyromonas species secrete broad-acting proteases capable of freely diffusing within the cervicovaginal niche. These proteases degrade collagens that are enriched within the cervix (type I) and chorioamniotic membranes (type IV), as well as fibrinogen, which inhibits clot formation. Bioinformatic queries confirmed the absence of gingipain orthologs and identified five serine, cysteine, and metalloprotease candidates in each species. Inhibition assays revealed that each species’ proteolytic activity can be partially attributed to a secreted metalloprotease with broad substrate specificity that is distantly related to the P. gingivalis endopeptidase PepO. This characterization of virulence activities in vaginal Porphyromonas species highlights their potential to alter the homeostasis of reproductive tissues and harm human pregnancy through clotting disruption, fetal membrane weakening, and premature cervical remodeling.

Evaluating the Efficacy of Eradicating Gardnerella vaginalis Vaginal Colonization With Amoxicillin: A Randomized, Double-Blind, Phase 2 Study

BACKGROUND

Research suggests that Gardnerella vaginalis (GV) is the keystone pathogen in bacterial vaginosis (BV). Knowledge gaps exist regarding the role of GV eradication in the development of BV. This study was designed to test the hypothesis that vaginal colonization with GV could be eradicated by treatment of women without BV with amoxicillin, a drug highly active against GV. If GV is necessary for the development of BV, then eradication of GV may prevent the development of BV.

METHODS

We conducted a randomized control trial of amoxicillin 500 mg twice daily versus placebo for 7 days in women aged 18 to 45 years without vaginitis who screened positive for vaginal colonization with GV by quantitative polymerase chain reaction. Test-of-cure visit for GV was conducted at day 21.

RESULTS

One hundred seventy-two women met preliminary criteria and were screened for enrollment. Ninety-seven GV-positive women were randomized to receive amoxicillin versus placebo. Eradication of GV occurred in 21% of women randomized to amoxicillin versus 16% on placebo (P = 0.757). In the 4 weeks between screening and test-of-cure visit, 16 of 92 (17%) of participants developed Nugent scores greater than 3 with 8 of 92 (9%) having BV. All of these were in participants in whom GV was not eradicated (P = 0.035).

CONCLUSIONS

The study failed to show a benefit of treatment with amoxicillin to eradicate GV. No participants in whom GV was eradicated had progression to abnormal vaginal flora during the study period.

The Female Reproductive Tract Microbiome-Implications for Gynecologic Cancers and Personalized Medicine

The microbial colonization of the lower female reproductive tract has been extensively studied over the past few decades. In contrast, the upper female reproductive tract including the uterine cavity and peritoneum where the ovaries and fallopian tubes reside were traditionally assumed to be sterile under non-pathologic conditions. However, recent studies applying next-generation sequencing of the bacterial 16S ribosomal RNA gene have provided convincing evidence for the existence of an upper female reproductive tract microbiome. While the vaginal microbiome and its importance for reproductive health outcomes has been extensively studied, the microbiome of the upper female reproductive tract and its relevance for gynecologic cancers has been less studied and will be the focus of this article. This targeted review summarizes the pertinent literature on the female reproductive tract microbiome in gynecologic malignancies and its anticipated role in future research and clinical applications in personalized medicine.

Megasphaera lornae sp. nov., Megasphaera hutchinsoni sp. nov., and Megasphaera vaginalis sp. nov.: novel bacteria isolated from the female genital tract

Six strictly anaerobic Gram-negative bacteria representing three novel species were isolated from the female reproductive tract. The proposed type strains for each species were designated UPII 199-6^T, KA00182^T and BV3C16-1^T. Phylogenetic analyses based on 16S rRNA gene sequencing indicated that the bacterial isolates were members of the genus Megasphaera. UPII 199-6^T and KA00182^T had 16S rRNA gene sequence identities of 99.9 % with 16S rRNA clone sequences previously amplified from the human vagina designated as Megasphaera type 1 and Megasphaera type 2, members of the human vaginal microbiota associated with bacterial vaginosis, preterm birth and HIV acquisition. UPII 199-6^T exhibited sequence identities ranging from 92.9 to 93.6 % with validly named Megasphaera isolates and KA00182^T had 16S rRNA gene sequence identities ranging from 92.6-94.2 %. BV3C16-1^T was most closely related to Megasphaera cerevisiae with a 16S rRNA gene sequence identity of 95.4 %. Cells were coccoid or diplococcoid, non-motile and did not form spores. Genital tract isolates metabolized organic acids but were asaccharolytic. The isolates also metabolized amino acids. The DNA G+C content for the genome sequences of UPII 199-6^T, KA00182^T and BV3C16-1^T were 46.4, 38.9 and 49.8 mol%, respectively. Digital DNA-DNA hybridization and average nucleotide identity between the genital tract isolates and other validly named Megasphaera species suggest that each isolate type represents a new species. The major fatty acid methyl esters include the following: C_12 : 0, C_16 : 0, C_16 : 0 dimethyl acetal (DMA) and summed feature 5 (C_15 : 0 DMA and/or C_14 : 0 3-OH) in UPII 199-6^T; C_16 : 0 and C_16 : 1 cis 9 in KA00182^T; C_12 : 0; C_14 : 0 3-OH; and summed feature 5 in BV3C16-1^T. The isolates produced butyrate, isobutyrate, and isovalerate but there were specific differences including production of formate and propionate. Together, these data indicate that UPII 199-6^T, KA00182^T and BV3C16-1^T represent novel species within the genus Megasphaera. We propose the following names: Megasphaera lornae sp. nov. for UPII 199-6^T representing the type strain of this species (=DSM 111201^T=ATCC TSD-205^T), Megasphaera hutchinsoni sp. nov. for KA00182^T representing the type strain of this species (=DSM 111202^T=ATCC TSD-206^T) and Megasphaera vaginalis sp. nov. for BV3C16-1^T representing the type strain of this species (=DSM 111203^T=ATCC TSD-207^T).