Gardnerella is a genus of gram-variable-staining facultative anaerobic bacteria of which G. vaginalis is the only species. It grows as small, circular, convex, gray colonies on chocolate agar. Colistin-oxolinic acid blood agar is a selective medium for G. vaginalis.

Bacterial vaginosis results in some women as a result of disruption of the normal vaginal microflora. Lactobacillus population in the vagina is responsible for the acidic environment. Prescription antibiotics with anaerobic coverage can be given to eliminate the G. vaginalis and allow balance of bacteria to be restored.

It can be detected from blood, urine, and pharynx although typically isolated in genital cultures. It is not a sexually transmitted. It can be isolated from women without any signs or symptoms of infection.

The cell wall is gram-positive but is very thin so it can appear as gram-positive or gram-negative under the microscope. Protease and sialidase enzyme activities frequently accompany G. vaginalis.