Antimicrobial effects of Sophora Flavescens Alkaloids on metronidazole-Resistant Gardnerella vaginalis in planktonic and biofilm formation

Abstract Objectives: This study aims to explored the effects and mechanisms of Sophora Flavescens Alkaloids (SFAs) on metronidazole-resistant Gardnerella vaginalis under planktonic and biofilm conditions.Methods: The main components of SFAs were analyzed using HPLC. Clinical strains were cultured from the vaginal secretions of BV patients, followed by PCR and 16s rRNA gene sequencing identification. According to the 2012 CLSI guidelines for anaerobic drug sensitivity testing, the sensitivity of Gardnerella vaginalis to metronidazole and SFAs were determined using the microdilution broth method. The formation of biofilms was evaluated, and the biofilm microstructure was observed using scanning electron microscopy.Results: The main active contents of SFAs were matrine and oxymatrine. Nineteen metronidazole-resistant strains were isolated and identified (minimum inhibitory concentration, MIC≥32 μg/mL), of which four clinical strains were observed to be strong biofilm producer and the final minimum biofilm inhibitory concentration (MBIC) of metronidazole was increased to 512 μg/mL. SFAs could not only inhibited the growth of metronidazole-resistant Gardnerella vaginalis in planktonic (MIC: 0.3125-1.25 mg/mL), but also eliminated the biofilm formation (MBIC: 0.625-1.25 mg/mL). Also, there was less biomass biofilm formation which was sparse and relatively thin. In the high-magnification scanning electron, it was observed that the water channels were destroyed, and furturemore, the biofilm morphology changed from a thick to flaky shape and was nearly depleted.Conclusions: Our results indicate that SFAs could not only inhibite the growth of metronidazole-resistant Gardnerella vaginalis in planktonic and biofilm levels, but also destroyed the biofilm morphology and microstructure, which may contribute to the prevention of BV recurrence.