Gardnerella vaginalis

The lead bacterium of bacterial vaginosis (BV). It displaces protective lactobacilli → an amine-like odour, grey-white discharge, a raised pH above 4.5.

How Gardnerella vaginalis lives in the vagina

Gardnerella vaginalis is a short rod-shaped bacterium that can live with or without oxygen. It is now known that several closely related species with differing properties lie behind the name. Gardnerella is also found in small amounts in many women without complaints. Normally, lactobacilli keep the vagina acidic by producing lactic acid; Gardnerella copes with this environment but is kept in check within it. Whether Gardnerella actively displaces the lactobacilli or exploits a gap that has arisen for other reasons is debated in research.

How Gardnerella affects the vaginal lining and the immune system

Gardnerella adheres to the cells of the vaginal lining and forms a biofilm there – a layer of bacteria enclosed in slime; lining cells covered with bacteria are visible under the microscope as “clue cells”. The toxin vaginolysin damages cell membranes, and the enzyme sialidase breaks down the protective mucus layer and antibodies. The biofilm serves as a scaffold for other bacteria that do not need oxygen; these produce amines such as trimethylamine, putrescine and cadaverine, which cause the odour and raise the pH further. Because only a few immune cells usually migrate in during this process, it is called a vaginosis rather than an inflammation.

What happens when Gardnerella multiplies heavily?

If Gardnerella multiplies heavily, the flora tips into bacterial vaginosis: fewer lactobacilli, more bacteria that do not need oxygen, a higher pH and a weakened mucus layer. In studies, bacterial vaginosis has been linked with greater susceptibility to sexually transmitted infections, with premature births and with ascending infections after procedures on the womb. The fact that vaginosis frequently recurs is explained, among other things, by the biofilm protecting the bacteria and by remnants of it being able to remain on the lining.

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