Identification of intrinsically metronidazole-resistant clades of Gardnerella vaginalis

Diagn Microbiol Infect Dis. 2016 Jan;84(1):1-3. doi: 10.1016/j.diagmicrobio.2015.10.006. Epub 2015 Oct 8.


Gardnerella vaginalis is associated with bacterial vaginosis (BV), the most common cause of vaginal discharge. Metronidazole is a front-line therapy for BV, and treatment failure and recurrent disease are common problems. Whole-genome sequencing studies have revealed that G. vaginalis has a population structure that consists of 4 clades: clades 1 and 3 are associated with BV, whereas clades 2 and 4 are not. To determine if metronidazole susceptibility is associated with population structure, we analyzed 87 clinical isolates and found that metronidazole resistance (MIC ≥32 μg/mL) was highly associated with clade (P<0.0001), as 14/14 clade 3 isolates (100%) and 22/22 clade 4 isolates (100%) exhibited resistance, compared to only 16/37 clade 1 isolates (35%) and 1/14 clade 2 isolates (7.1%). The identification of intrinsically metronidazole-resistant G. vaginalis clades will facilitate future studies on the relationship between metronidazole resistance and BV treatment failure.

Keywords: Bacterial vaginosis; Gardnerella vaginalis; Metronidazole.

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Drug Resistance, Bacterial*
  • Female
  • Gardnerella vaginalis / classification
  • Gardnerella vaginalis / drug effects*
  • Gardnerella vaginalis / genetics
  • Gardnerella vaginalis / isolation & purification*
  • Genotype*
  • Gram-Positive Bacterial Infections / microbiology
  • Humans
  • Metronidazole / pharmacology*
  • Microbial Sensitivity Tests
  • Vaginosis, Bacterial / microbiology


  • Anti-Bacterial Agents
  • Metronidazole