In vitro antimicrobial activity of Schinus terebinthifolia Raddi metronidazole, clindamycin against Lactobacillus gasseri lauer and kandler and its implications in recurrent bacterial vaginosis

Bacterial vaginosis (BV) is a highly prevalent condition and the leading cause of vaginal discharge globally. It is characterized by dysbiosis, wherein hydrogen peroxide- and lactic acid-producing lactobacilli are replaced by anaerobic bacteria at elevated concentrations, including Gardnerella vaginalis, Prevotella spp., Mobiluncus spp., Atopobium spp., and others. BV can be self-diagnosed based on classical symptoms or clinically and laboratory-confirmed using Amsel criteria or Nugent scoring. Recommended treatments include oral metronidazole, secnidazole, and tinidazole, as well as vaginal formulations of metronidazole gel, clindamycin cream, and Schinus terebinthifolia Raddi gel. This study aimed to evaluate the effects of clindamycin vaginal cream, metronidazole vaginal gel, and S. terebinthifolia Raddi vaginal gel on the growth and survival of Lactobacillus gasseri ATCC 19992 in vitro. The plate perforation method was employed, creating 6 mm wells into which the test samples were inoculated. Plates were incubated at 30°C for 48 hours, followed by visual analysis. Results indicated that L. gasseri was resistant to S. terebinthifolia Raddi vaginal gel, as no inhibition zones were observed. In contrast, moderate susceptibility to metronidazole vaginal gel and high sensitivity to clindamycin vaginal cream were noted. Since lactobacilli, particularly L. gasseri, comprise over 95% of the vaginal microbiota, maintaining this population is critical for vaginal health. The observed inhibitory effects of clindamycin and metronidazole on L. gasseri suggest these treatments may disrupt the vaginal microbiome, potentially leading to recurrent BV when used for its management.