Screening The Lactic Acid Bacteria Which Inhibit Gardnerella Vaginalis And Researching On Biological Characteristics

The healthy vagina were colonized by a variety of bacteria, including probiotics and opportunistic pathogens, which were dynamically balanced in the maintenance of vagina health. However, sometimes, such as lower estrogen levels, sexual behavior, antibiotics, leading to overgrowth of bacteria in the vagina such as (Gardnerella vaginalis, Gv), disruption of lactobacilli.It would break the balance of the flora, causing vaginal infections.Bacterial vaginosis (BV) was widely believed to be the most frequently encountered in vaginal infection in medical practice, metronidazole and clindamycin were currently the recommended treatment of choice for BV.Although antibiotic therapy had been shown to eliminate BV-associated organisms,there was an extremely high recurrence rate and enhanced the resistance of some pathogens.In summary, it was urgently need to find a therapy to restore the normal vaginal flora by re-colonising with lactobacilli.It has been demonstrated that strains of lactobacilli to cure B V was a viable, efficient, wide development space method. Currently, foreign scholars had isolated several strains, domestic only one vaginal lactobacillus preparations, namely German Lactobacillus DM8909.To enrich the diversity of strains, there is an urgent need to sreen more lactobacilli.The purpose of this study was to isolate the lactobacilli inhibited G. vaginalis from vaginal secretions of healthy women. In order to evaluate their significance, the antimicrobial, identification, acid and hydrogen peroxide production,mechanism of adhesion to Hela cells, as well as safety evaluation,were estimated.The results showed that all of the18lactobacilli strains had inhibition effect to indicator pathogen and3of them (3, N7,15) were the best. Data showed that the control group had a lg7.26CFU/mL of G.v; while the cell-free supernatants of those three strains were added into the BHIs, it became lg5.09CFU/mL, lg5.42CFU/mL, lg5.44CFU/mL respectively; and that of the commercial strain DM8909was lg5.95CFU/mL.The inhibition effects of the3strains were significantly stronger than the commercial strain DM8909by the SPSS data analysis software (p<0.05). The3of lactobacilli strains also decreased the viability of S, aureus and E. coli. When the pH of cell-free supernatants were adjusted to7.0, they were between Ig7.5CFU/mL and lg7.6CFU/mL, and there had no significant difference with the control group (p<0.05).Due to the strains almost had no antibacterial activity after pH of cell-free supernatants were adjusted to 7.0,we suggested that the organic acid produced by lactobacilli most important for antagonizing pathogenic bacteria. Then the3strains were identified as Lactobacillus plantarum. The biological characteristics studies were growth characteristics of the4strains,acid production after growth of the lactobacilli in liquid culture, production of hydrogen peroxide(H2O2) and tolerance in low acid. The results showed that all3isolates produced a highly acidic environment after growth in liquid medium(pH was3.50,pH of control was3.95) and had a weakly ability to produce H2O2. In acid tolerance test, survival rate of the3strains were up to about70%in pH3.0after8h, the results showed that the isolates could survive well in the acid environment of the vagina.Finally selecting3%N7and15as the research object, using Hela cells which were the most similar to human vaginal epithelial cell as a model to assess the adhesive ability of the4strains. The results showed that4strains were strongly adherent to Hela cells. Then studied how lactobacilli prevent binding of G. vaginalis onto Hela cells, three types of interaction were performed:Exclusion Group (lactobacilli and Hela followed by Gardnerella vaginal), Competition Group (lactobacilli, Hela and Gardnerella vaginal together) and Displacement Group(Gardnerella vaginal and Hela followed by the addition of lactobacilli). Studies revealed that there was variation among the three types. Further more,there had a significant difference with the control in every way (p<0.05). All4strains displayed the ability of blocking Gardnerella vaginal adherence to Hela cells, but there had no significant difference among the4strains. Exclusion Group was the most effective, and Displacement Group was the most weak.The antibiotic susceptibility tests showed that isolates were susceptible to all tested antibiotics except clindamycin and vancomycin and streptomycin. Hemolytic test showed that the isolates were not hemolysis(y hemolysis), non-pathogenic to humans.On the basis of the abilities of3Lactobacillus plantarum strains from women’s vagina to inhibit Gardnerella vaginal strongly and produce acid, H2O2,as well as its inhibition of Gardnerella vaginal adherence to Hela cells, it is likely that the3Lactobacillus plantarum strains could be candidates for use as probiotics for bacterial vaginosis and were worth for further evaluation and development.