Effect of pH on the adherence, surface hydrophobicity and the biofilm formation of Gardnerella vaginalis

Background: Bacterial vaginosis is a common cause of the abnormal vaginal discharge in women of the reproductive age group. Although bacterial vaginosis is prevalent, not much progress has been made in identifying the factors which are responsible for and those which are associated with bacterial vaginosis and its pathophysiology. Here, we would like to evaluate the effect of the change in the pH of the vagina on the virulence factors of Gardnerella vaginalis, the main organism which has been indicated in this vaginal condition. Objective: The objective of the present study was to observe the effect of pH on the adherence, surface hydrophobicity and the biofilm formation of 10 strains of Gardnerella vaginalis which were isolated from cases of bacterial vaginosis. Result: We found that the adherence to the vaginal epithelial cells and the surface hydrophobicity was maximum at a lower pH (pH- 3,4,5) and minimum at a higher pH (pH- 6,7), but the pH did not have a significant effect on the biofilm formation. Conclusion: An increase in the pH of the vagina which is observed during bacterial vaginosis, probably occurs much later during the disease. During the early part of the disease, the bacteria adhere to the vaginal epithelium, multiply in large numbers and form a thick biofilm which is not affected by the rise in pH, which occurs probably due to the metabolic activities of this large bacterial population. This also explains the fact that all women with bacterial vaginosis do not have an elevated vaginal pH.