High levels of Gardnerella vaginalis detected with an oligonucleotide probe combined with elevated pH as a diagnostic indicator of bacterial vaginosis.

We have demonstrated a new approach to diagnosing bacterial vaginosis (BV) that is based on measuring the concentration of Gardnerella vaginalis in vaginal fluid with DNA probes. G. vaginalis is virtually always present at high concentrations in women who have BV but is also detected frequently in normal women, usually at concentrations of less than 10(7) CFU/ml of vaginal fluid. Elevated vaginal pH is another sensitive indicator of BV, although it can occur in conjunction with other conditions. We have proposed that quantitative measurements of G. vaginalis using specific DNA probes can serve as a useful aid in diagnosing BV, provided the vaginal pH is above 4.5. To test this hypothesis, a group of 113 women were first evaluated for BV by the standard set of clinical signs. Vaginal washes were collected, and aliquots were analyzed by quantitative culture for the concentration of G. vaginalis. Portions of these same samples were immobilized on nylon filters, along with standards for quantitation. The filters were incubated with a radiolabelled oligonucleotide specific for G. vaginalis 16S rRNA, and the subsequent autoradiographs were examined to determine levels of G. vaginalis in each sample. G. vaginalis at concentrations of greater than or equal to 2 x 10(7) CFU/ml and vaginal pH of greater than 4.5 were then analyzed for concurrence with the diagnoses based on clinical criteria. Results of this slot blot analysis gave a sensitivity of 95%, correctly categorizing 41 of 43 BV-positive specimens, and a specificity of 99%, correctly identifying 69 of 70 BV-negative specimens, compared with diagnosis based on clinical criteria.