Evaluation of a rapid method for the detection of vaginal group B streptococci in women in labor.

Group B streptococci infection is an important cause of neonatal morbidity and mortality. Effective therapeutic intervention has been prevented to date by our inability to rapidly detect vaginal colonization. Material obtained from the lower vagina of 414 women in labor was cultured, incubated in modified Islam serum starch broth and observed on the ward for the production of orange carotenoid pigment specific for group B streptococci. Subcultures yielded 48 true group B streptococci-positive results. For the Islam broth, the pigment appeared in 2 to 22.5 hours (median, 12.5 hours). The test was shown to have a sensitivity of 96% and a specificity of 100% for group B streptococci. This study demonstrated a simple inexpensive method of detecting vaginal group B streptococci colonization which does not require sophisticated 24-hour laboratory facilities. The method holds promise as a screening test for future intervention studies.