Cervical Gram stain for rapid detection of colonization with beta-streptococcus.

The group B beta-hemolytic streptococcus has been implicated in significant maternal and neonatal infections. The usual criteria for identifying the organism has been culture. A preliminary prospective study of the applicability of a simple, rapid, and readily available inexpensive screening tool, the Gram stain, was evaluated in 98 high-risk patients (premature rupture of the membranes and/or premature labor). In this selected population, cervical Gram stain was found to have a 98% negative predictive value for subsequent culture-proven group B beta-hemolytic streptococcus colonization. The sensitivity, specificity, and positive predictive values were, respectively, 93, 69, and 33%. Gram stain may be an appropriate test to assist in evaluation of group B beta-hemolytic streptococcus colonization in an at-risk population.