Background: Group B Streptococcus (GBS) can be transmitted to neonates during delivery through the birth canal. As awareness of neonatal GBS infections is increasing, more rapid and efficient screening tests are required. The aim of this study was to evaluate the performance of ChromID STRB (bioMérieux, France) and PCR compared with the standard culture method.

Methods: Recto-vaginal swabs were collected from 775 pregnant women from April 2016 to March 2017. Cotton swab cultures were grown in LIM broth overnight and then subcultured onto blood agar plates and ChromID STRB. PCR was carried out to detect atr genes specific for GBS.

Results: The carrier rate of GBS was 5.9% (46/775). The sensitivity, specificity, positive predictive value, and negative predictive value were 83.8%, 99.3%, 86.1%, and 99.2%, respectively, for ChromID STRB and 89.2%, 99.6%, 91.7%, and 99.5%, respectively for PCR. Both ChromID STRB and PCR detected 6 more cases compared to the standard culture.

Conclusion: Chromogenic agar, ChromID STRB, and PCR using the atr gene showed excellent performance to screen for GBS. To administer prophylactic antibiotics efficiently, either selective chromogenic agar or PCR could be used in addition to the standard culture. (Ann Clin Microbiol 2017;20:103-108)