Gardnerella

Gardnerella is a genus of Gram-variable, non-spore-forming, non-motile bacteria in the phylum Actinobacteria. The best known species is Gardnerella vaginalis, which is closely associated with bacterial vaginosis (BV), a common polymicrobial dysbiosis of the vaginal microbiota in women of reproductive age.

In healthy individuals, Lactobacillus species typically predominate in the vagina; BV involves a shift toward diverse anaerobes, with G. vaginalis frequently present and capable of forming biofilms on the vaginal epithelium. The organism may express virulence factors such as vaginolysin, a cholesterol-dependent cytolysin, and enzymes like sialidases that contribute to mucus degradation and adherence to surfaces.

Clinical relevance and diagnosis: BV presents with vaginal discharge that is often thin and gray, reduced lactobacilli with an elevated vaginal pH, and sometimes a fishy odor. Diagnosis can be made using Amsel criteria in clinical practice or Nugent scoring of Gram-stained vaginal smears in the laboratory. Culturing Gardnerella vaginalis is not routinely used for diagnosis, though culture or molecular assays (PCR) can detect G. vaginalis and characterize BV-associated microbial communities.

Treatment and prognosis: BV is typically treated with antibiotics such as metronidazole or tinidazole (oral or intravaginal formulations) or with clindamycin for those intolerant to nitroimidazoles. Recurrence is common. BV is associated with adverse pregnancy outcomes and a higher risk of acquiring or transmitting sexually transmitted infections, including HIV.