THE EFFECT OF PH ON GROWTH AND SUCCINATE PRODUCTION BY PREVOTELLA BIVIA

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 i solated 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 c ontinuous culture system. At pH 6.0, P. bivia was present at a mean ma ximal 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 f ollowing a pH change to either 5.5 or 5.0 for all strains, indicated t hat the organism was pi-I-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, menarch eal women also correlated the concentration of P. bivia with vaginal p H (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 su rrogate marker for vaginal pH.