Response of Gardnerella vaginalis biofilm to 5 days of moxifloxacin treatment

Polymicrobial communities are often recalcitrant to antibiotics. We tested whether the polymicrobial Gardnerella vaginalis biofilm can be eradicated with moxifloxacin. Twenty women with bacterial vaginosis were treated with 400 mg moxifloxacin for 5 days. The changes in the occurrence and proportions of Gardnerella, Atopobium and Lactobacillus spp. were assessed using FISH. The bacterial biofilm was investigated using desquamated epithelial cells of spontaneously voided urine and sections of vaginal biopsies. Fifteen of 20 women showed a significant and sustained clinical response to moxifloxacin according to Amsel and Nugent criteria. The concentrations of adherent bacteria decreased significantly. The incidence and proportion of Atopobium declined sustainably. The proportions of Lactobacillus in the biofilm mass increased following therapy. Initially, Gardnerella was the main component of the polymicrobial biofilm. Following treatment, Gardnerella was not accessible to FISH in the urine and vaginal samples of 75% of all women. Ten to 12 weeks after the end of therapy, Gardnerella biofilm was cumulatively present in 40%. This was not due to newly acquired disease, but due to reactivation of the persisting, but biochemically inactive biofilm. Despite clear clinical efficacy, and initially definite suppression of the biofilm, moxifloxacin was, similar to metronidazole, not able to eradicate the Gardnerella vaginalis biofilm in all patients.