Rapid Group B streptococcus screening methods in late pregnancy and the maternal-neonatal outcomes

Abstract

To study the sensitivity of the quantitative fluorescence polymerase chain reaction (QF-PCR) in detecting group B streptococcus (GBS) in late pregnant women and the influence of vaginal/rectal GBS colonization on the maternal-neonatal outcomes. A total of 2020 swabs were taken from 505 women who received routine culture and QF-PCR screening at 35 and 37 weeks of gestation from September, 2013 to April, 2014 at Peking Union Medical College Hospital.For each subject, two vaginal and two rectal swabs were collected.Samples with discordant results from these two methods were further analyzed by gene sequence determination.GBS isolates were subjected to antimicrobial susceptibility testing using the Kirby-Bauer method.The laboratory results were collected and the pregnant outcomes were followed. Of the 38 GBS positive cases , GBS could be detected for 13 by both culture and QF-PCR methods, for 24 only by QF-PCR, for 1 exclusively by culture.GBS colonization rate, sensitivity and negative predictive value (NPV) for culture were 2.8%, 36.8%, and 95.1%, respectively.GBS colonization rate, sensitivity and negative predictive value (NPV) for QF-PCR were 7.3%, 97.4%, and 99.8%, respectively.There was significant difference between the two methods (P<0.001). A higher proportion of GBS were isolated from the rectum (6.7%) as compared to the vagina (2.8%) (P<0.01). GBS isolates were all (100%) sensitive to penicillins, cephalosporins, vancomycin and linezolid.Erythromycinresistance was present in 47.4% of the GBS isolates, while clindamycin resistance was present in 36.8%.Compared with the GBS negative group, the GBS positive group had higher incidence of gestational hypertension and colpitis mycotica (all P<0.05), but had similar incidence of maternal and neonatal outcomes, like neonatal infection, septicemia, puerperal disease. QF-PCR assay provides an accurate and rapid method for detecting GBS in late pregnancy.Rectum is also an important site for detection of GBS.Penicillin therapy remains an appropriate first-line antibiotic choice for intrapartum GBS chemoprophylaxis, with erythromycin and clindamycin resistance rate being high.The relationship between maternal GBS colonization and the pregnancy outcome needs to be further studied.