Colonization of the upper genital tract by vaginal bacterial species in nonpregnant women

Abstract

Objective: The objective of the study was to evaluate the upper genital tract (UGT) presence of vaginal bacterial species using sensitive molecular methods capable of detecting fastidious bacterial vaginosis (BV)-associated bacteria.

Study design: Vaginal swabs were collected prior to hysterectomy. The excised uterus was sterilely opened and swabs collected from the endometrium and upper endocervix. DNA was tested in 11 quantitative polymerase chain reaction (PCR) assays for 12 bacterial species: Lactobacillus iners, L crispatus, L jensenii, Gardnerella vaginalis, Atopobium vaginae, Megasphaera spp, Prevotella spp, Leptotrichia/Sneathia, BVAB1, BVAB2, BVAB3, and a broad-range16S ribosomal ribonucleic acid gene assay. Endometrial fluid was tested with Luminex and an enzyme-linked immunosorbent assay for cytokines and defensins and tissue for gene expression of defensins and cathelicidin.

Results: We enrolled 58 women: mean aged 43±7 years, mostly white (n=46; 79%) and BV negative (n=43; 74%). By species-specific quantitative PCR, 55 (95%) had UGT colonization with at least 1 species (n=52) or were positive by 16S PCR (n=3). The most common species were L iners (45% UGT, 61% vagina), Prevotella spp (33% UGT, 76% vagina) and L crispatus (33% UGT, 56% vagina). Median quantities of bacteria in the UGT were lower than vaginal levels by 2-4 log10 ribosomal ribonucleic acid gene copies per swab. There were no differences in the endometrial inflammatory markers between women with no bacteria, Lactobacillus only, or any BV-associated species in the UGT.

Conclusion: Our data suggest that the endometrial cavity is not sterile in most women undergoing hysterectomy and that the presence of low levels of bacteria in the uterus is not associated with significant inflammation.

Keywords: endometritis; endometrium; intrauterine bacteria; reproductive tract microbiota; sterile; upper genital tract infection; uterine cavity.

Conflict of interest statement

The authors report no conflicts of interest.

Copyright © 2015 Elsevier Inc. All rights reserved.

Figures

Figure 1. Distribution of upper genital tract bacterial colonization

A. Proportion of participants with detection of bacteria by species-specific qPCR in the vagina alone, both vagina and upper genital tract (UGT) and UGT alone. B. Comparison of mean quantity of bacteria in the vagina and UGT of women with either vaginal or upper genital tract detection of that species. * denotes comparisons that are significantly different (p

Figure 2. Comparison of vaginal and upper genital tract detection of bacteria

Detection and quantity of each species in the vagina and UGT for each participant, organized by Nugent score. Each bacterium is represented by a row, and the quantity is represented by a gradient of color, with darker colors representing higher quantities. The color gradients represent grouping of 1–100, 101–10,000, 10,000 – 1,000,000 and > 1,000,000 16S rRNA gene copies/swab. A white space means that the bacterium was not detected in that sample.

Figure 3. Endometrial immune markers

Comparison of markers of the immune response in the upper genital tract between women with no bacteria detected by PCR in the upper genital tract, only Lactobacillus species detected, or any non-Lactobacillus species detected. Numbers in boxes are multiple of the median, calculated by taking the median value for the whole cohort and dividing the individual group value by that number. There were no significant differences between these three groups. Values highlighted in red are higher than the group median, and those in blue are lower than the group median.