Changes in the Vaginal Microbiome during the Pregnancy to Postpartum Transition.

Substantial changes in the composition of the vaginal microbiome occur following the end of pregnancy. To identify potential drivers of microbiome changes in individual women during the pregnancy to postpartum transition, we evaluated vaginal samples from 48 pregnant women during their first and third trimesters and postpartum. We determined the species composition of vaginal communities and the vaginal fluid levels of compounds involved in mediating changes in host physiology and the immune system at each time point. We used linear mixed-effects models to characterize associations. Consistent with previous reports, but with a larger sample size, a US population, and variations in the dominant bacteria, the vaginal microbiome was found to be more diverse during the postpartum period. There was a lower abundance of Lactobacillus and significantly higher proportions of Streptococcus anginosus and Prevotella bivia. Moreover, we uniquely demonstrated that postpartum vaginal secretions were also altered postpartum. There were elevated levels of hyaluronan and Hsp70 and decreased levels of the D- and L-lactic acid isomers. We posit that these variations are consequences of alterations in the vagina after delivery that profoundly alter the host environment and, thus, lead to changes in the capability of different bacterial species to survive and proliferate.

Comparison of the Vaginal Microbiomes of Premenopausal and Postmenopausal Women.

For decades hormone therapy (HT) has been prescribed to treat the symptoms of menopause, such as vaginal dryness, itching and burning. Here we sought to compare the vaginal microbiomes of postmenopausal women who received low dose estrogen therapy to those of premenopausal and postmenopausal women, and to do so in conjunction with assessing the alleviation of symptoms associated with vaginal atrophy. In this study vaginal swab samples were obtained from 45 women who were classified as either premenopausal, postmenopausal, or postmenopausal and undergoing HT. The vaginal microbiomes of these women were characterized by 16S rRNA gene sequencing and bacterial abundances were quantified by qPCR. We found that the vaginal communities from our cohort could be divided into six clusters (A-F) based on differences in the composition and relative abundances of bacterial taxa. Communities in cluster A were dominated by Lactobacillus crispatus, and those of cluster B were dominated by Gardnerella vaginalis. Communities in cluster C had high proportions of L. iners, while those in cluster D were more even and included several co-dominant taxa. Communities in clusters E and F were dominated by Bifidobacterium and L. gasseri, respectively. The vaginal communities of most postmenopausal women receiving HT (10/15) were dominated by species of lactobacilli and belonged to clusters A, C, and F (P < 0.001). This sharply contrasts with vaginal communities of postmenopausal women without HT, most of which (10/15) were in cluster D, depleted of lactobacilli, and had about 10-fold fewer total bacteria (P < 0.05). The vaginal communities of women in each study group differed in terms of the dominant bacterial species composition and relative abundance. Those of postmenopausal women receiving HT significantly differed from those of postmenopausal women without HT and were most often dominated by species of Lactobacillus. Noteworthy, HT greatly improved vaginal atrophy scores, decreased vaginal pH, and significantly increased bacterial numbers in comparison to postmenopausal women not receiving HT.

Properties of Epithelial Cells and Vaginal Secretions in Pregnant Women When Lactobacillus crispatus or Lactobacillus iners Dominate the Vaginal Microbiome.

OBJECTIVE: Our objective was to determine differences in properties of vaginal epithelial cells and the composition of vaginal secretions when Lactobacillus crispatus or Lactobacillus iners are numerically dominant in the vaginal microenvironment of pregnant women. METHODS: The vaginal microbiomes of 157 first-trimester pregnant women were identified by classifying partial 16S gene sequences amplified from the V1 to V3 region of bacterial ribosomal 16S RNA genes. The extent of autophagy and cell stress in vaginal epithelial cells was determined by measuring the intracellular levels of p62 and the inducible 70-kDa heat shock protein (hsp70). Vaginal secretions were analyzed using a colorimetric assay for d- and l-lactic acid and by enzyme-linked immunosorbent assay for matrix metalloproteinase 8, neutrophil gelatinase-associated lipocalin, α-amylase, hyaluronan, calprotectin, S100A8, and extracellular matrix metalloproteinase inducer (EMMPRIN). RESULTS: L. crispatus was dominant in 69 (43.9%) women, while L iners dominated in 23 (14.6%) women. The median epithelial p62 levels were 0.41 and 4.26 ng/mL in women with L crispatus or L iners dominance, respectively ( P = .0035). The corresponding median hsp70 levels were 4.24 and 14.50 ng/mL, respectively ( P < .0001). The d-lactic acid concentration in vaginal fluid was highest in association with L crispatus dominance, while all other vaginal fluid compounds except for EMMPRIN were highest when L iners was dominant ( P< .03). CONCLUSION: Epithelial cells exhibit a higher level of autophagy, lower induction of stress-related hsp70, and release lower level of mediators when L crispatus is most abundant as compared to when L iners dominates the vaginal microbiota.

The composition of the vaginal microbiome in first trimester pregnant women influences the level of autophagy and stress in vaginal epithelial cells.

Epithelial cells lining the vagina are major components of genital tract immunity. The influence of the vaginal microbiome on properties of host epithelial cells is largely unexplored. We evaluated whether differences in the most abundant lactobacilli species or bacterial genera in the vagina of first trimester pregnant women were associated with variations in the extent of stress and autophagy in vaginal epithelial cells. Vaginal swabs from 154 first trimester pregnant women were analyzed for bacterial composition by amplification and sequencing of the V1-V3 region of bacterial 16S rRNA genes. Vaginal epithelial cells were lysed and autophagy quantitated by measurement of p62. Intracellular levels of the inducible 70kDa heat shock protein (hsp70), an indicator of cell stress and an autophagy inhibitor, were determined. When Lactobacillus crispatus was the most abundant member of the vaginal microbiota, epithelial p62 and hsp70 levels were lowest as compared to when other bacterial taxa were most abundant. The highest concentrations of p62 and hsp70 were associated with Streptococcus and Bifidobacterium abundance. The p62 level associated with Gardnerella abundance was lower than that observed when lactobacilli other than L. crispatus were most abundant. In conclusion, in the first trimester of pregnancy the abundance of different bacterial taxa is associated with variations in autophagy and magnitude of the stress response in vaginal epithelial cells.

Influence of Pregnancy History on the Vaginal Microbiome of Pregnant Women in their First Trimester.

Pregnancy permanently alters maternal anatomy, physiology and immunity. We evaluated if the vaginal microbiome differed between women with a first or subsequent conception. Relative abundance of bacteria in the vaginal microbiome in first trimester pregnant women, 52 with their first known conception, 26 with a prior spontaneous or induced abortion but no deliveries and 77 with at least one prior birth, was determined by classifying DNA sequences from the V1-V3 region of bacterial 16 S rRNA genes. Lactobacillus crispatus was the numerically most abundant bacterium in 76.4% of women with a first conception, 50.0% with only a prior spontaneous or scheduled abortion and 22.2% with a prior birth (p ≤ 0.01). L. iners was the most abundant bacterium in 3.8% of women with a first conception as compared to 19.2% (p = 0.03) and 20.8% (p = 0.03) in those with a prior abortion or birth, respectively. Gardnerella as the most abundant bacterial genus increased from 3.8% in women with a first conception to 15.4% and 14.3% in those with a prior abortion or birth, respectively (p > 0.05). L. iners dominance was also associated with a history of spontaneous abortion (p ≤ 0.02). The composition of the vaginal microbiome and its influence on pregnancy outcome varies with pregnancy history.

Vaginal microbiome of reproductive-age women.

The means by which vaginal microbiomes help prevent urogenital diseases in women and maintain health are poorly understood. To gain insight into this, the vaginal bacterial communities of 396 asymptomatic North American women who represented four ethnic groups (white, black, Hispanic, and Asian) were sampled and the species composition characterized by pyrosequencing of barcoded 16S rRNA genes. The communities clustered into five groups: four were dominated by Lactobacillus iners, L. crispatus, L. gasseri, or L. jensenii, whereas the fifth had lower proportions of lactic acid bacteria and higher proportions of strictly anaerobic organisms, indicating that a potential key ecological function, the production of lactic acid, seems to be conserved in all communities. The proportions of each community group varied among the four ethnic groups, and these differences were statistically significant [χ(2)(10) = 36.8, P < 0.0001]. Moreover, the vaginal pH of women in different ethnic groups also differed and was higher in Hispanic (pH 5.0 ± 0.59) and black (pH 4.7 ± 1.04) women as compared with Asian (pH 4.4 ± 0.59) and white (pH 4.2 ± 0.3) women. Phylotypes with correlated relative abundances were found in all communities, and these patterns were associated with either high or low Nugent scores, which are used as a factor for the diagnosis of bacterial vaginosis. The inherent differences within and between women in different ethnic groups strongly argues for a more refined definition of the kinds of bacterial communities normally found in healthy women and the need to appreciate differences between individuals so they can be taken into account in risk assessment and disease diagnosis.

Comparison of self-collected and physician-collected vaginal swabs for microbiome analysis.

To our knowledge, no data are available on whether the microbial species composition and abundance sampled with self-collected vaginal swabs are comparable to those of swabs collected by clinicians. Twenty healthy women were recruited to the study during a routine gynecological visit. Eligible women were between 18 and 40 years old with regular menstrual cycles. Participants self-collected a vaginal swab using a standardized protocol and then were examined by a physician, who collected an additional five swabs from the lateral wall of the mid-vagina. In this study, the self-collected and three physician-obtained swabs were analyzed and compared using terminal restriction fragment length polymorphism and sequence analyses of the 16S rRNA genes. Vaginal microbial community comparative statistical analyses of both T-RFLP and 16S rRNA gene sequence datasets revealed that self-collected vaginal swabs sampled the same microbial diversity as physician collected swabs of the mid-vagina. These findings enable large-scale, field-based studies of the vaginal microbiome.

Bacterial succession in a glacier foreland of the High Arctic.

Succession is defined as changes in biological communities over time. It has been extensively studied in plant communities, but little is known about bacterial succession, in particular in environments such as High Arctic glacier forelands. Bacteria carry out key processes in the development of soil, biogeochemical cycling and facilitating plant colonization. In this study we sampled two roughly parallel chronosequences in the foreland of Midre Lovén glacier on Svalbard, Norway and tested whether any of several factors were associated with changes in the structure of bacterial communities, including time after glacier retreat, horizontal variation caused by the distance between chronosequences and vertical variation at two soil depths. The structures of soil bacterial communities at different locations were compared using terminal restriction fragment length polymorphisms of 16S rRNA genes, and the data were analyzed by sequential analysis of log-linear statistical models. Although no significant differences in community structure were detected between the two chronosequences, statistically significant differences between sampling locations in the surface and mineral soils could be demonstrated even though glacier forelands are patchy and dynamic environments. These findings suggest that bacterial succession occurs in High Arctic glacier forelands but may differ in different soil depths.