Presence of a polymicrobial endometrial biofilm in patients with bacterial vaginosis

Abstract

Objective: To assess whether the bacterial vaginosis biofilm extends into the upper female genital tract.

Study design: Endometrial samples obtained during curettage and fallopian tube samples obtained during salpingectomy were collected. Endometrial and fallopian tube samples were analyzed for the presence of bacteria with fluorescence-in-situ-hybridisation (FISH) analysis with probes targeting bacterial vaginosis-associated and other bacteria.

Results: A structured polymicrobial Gardnerella vaginalis biofilm could be detected in part of the endometrial and fallopian tube specimens. Women with bacterial vaginosis had a 50.0% (95% CI 24.0-76.0) risk of presenting with an endometrial Gardnerella vaginalis biofilm. Pregnancy (AOR = 41.5, 95% CI 5.0-341.9, p<0.001) and the presence of bacterial vaginosis (AOR = 23.2, 95% CI 2.6-205.9, p<0.001) were highly predictive of the presence of uterine or fallopian bacterial colonisation when compared to non-pregnant women without bacterial vaginosis.

Conclusion: Bacterial vaginosis is frequently associated with the presence of a structured polymicrobial Gardnerella vaginalis biofilm attached to the endometrium. This may have major implications for our understanding of the pathogenesis of adverse pregnancy outcome in association with bacterial vaginosis.

Figure 1. Gardnerella dominated polymicrobial biofilm cover the vaginal cells in urine.

Urine sediment from a woman with a Gardnerella dominated polymicrobial vaginal biofilm. Left panel: DAPI stain of urine sediment with desquamated epithelial cells, right panel: the same microscopic field hybridized with Gard C5 FISH probe, dark red fluorescence at magnification ×400.

Figure 2. Gardnerella dominated polymicrobial biofilm attached to the endometrium.

Prolific Gardnerella dominated biofilm within follicular (left panel) and luteal (right panel) endometrium. Hybridization is performed with Gard C3 orange fluorescence FISH probe, at magnification ×1000. The anatomic location of bacteria within the endometrium excludes the possibility of contamination.

Figure 3. Endometrial sample free of bacteria.

An example of negative hybridization with the universal Eub 338-C3 probe with no bacteria on the endometrium showing fluoresence (magnification ×1000).

Figure 4. Bacteria other than Gardnerella colonising the endometrial epithelium.

Singular bacteria positively hybridize with the Eub 338 -C3 probe specific for all bacteria are located on the endometrium (orange fluorescence magnification ×1000). These bacteria are negative, when hybridized with the Gardnerella probe, never build biofilms and are “planktonic”.