The Effect of pH on Growth and Succinate Production byPrevotella bivia

Abstract

Prevotella bivia is frequently isolated as a vaginal commensal and is also one of several organisms associated with bacterial vaginosis. In an attempt to define the role of this organism as part of the vaginal ecosystem, the influence of pH on viable cell density and short chain fatty acid (SCFA) production was examined. Seven strains of P. bivia isolated from the vagina of healthy women were grown in vaginal defined medium for 3 d at pH values 6.0, 5.5, 5.0 and 4.5 using an in vitro continuous culture system. At pH 6.0, P. bivia was present at a mean maximal cell density of log 10 7.93 colony forming units per ml (CFU/ml). A mean decrease in viable cell density of log 10 1.39 CFU/ml/day following a pH change to either 5.5 or 5.0 for all strains, indicated that the organism was pH-sensitive. Succinate, the only SCFA detected during growth in this system, was produced at a mean concentration of 0.025 mM at maximal cell density. Regression analysis of information contained in an in vivo data set of observations from healthy, menarcheal women also correlated the concentration of P. bivia with vaginal pH ( P =0.049). The apparent sensitivity of this organism to pH suggests that the concentration of P. bivia within the vagina may serve as a surrogate marker for vaginal pH. Keywords: Prevotella bivia , bacterial vaginosis, pH, succinate, vagina.