Objective: To study the incidences of group B streptococcus (GBS) colonization in pregnant women and GBS infection in their preterm infants, and to investigate the risk factors for GBS colonization in preterm infants.
Methods: A total of 859 women who delivered before term from January 2017 to January 2018 were enrolled in this prospective cohort study. Bacterial culture was performed for GBS using the swabs collected from the rectum and the lower 1/3 of the vagina of the pregnant women on admission. A total of 515 of the above cases underwent real-time PCR assay for testing of GBS DNA. Bacterial culture was performed for GBS using the oropharyngeal secretion, gastric fluid or blood samples in preterm infants born to the 859 pregnant women. Peripheral blood samples from the pregnant women and umbilical cord blood samples from their preterm infants were collected to determine the level of anti-GBS capsular polysaccharide antibody. The incidence of GBS infection and perinatal risk factors for GBS colonization in the preterm infants were examined.
Results: The positive rate for GBS in the rectal and vaginal cultures was 14.8% (127/859) among the 859 pregnant women, and the positive rate in the GBS DNA testing was 15.1% (78/515). There were 976 live-birth preterm infants delivered by 859 pregnant women, and 4.4% (43/976) of whom were GBS positive. Four preterm infants had early-onset GBS diseases, including pneumonia in two cases and sepsis in two cases. In 127 preterm infants delivered by 127 GBS-positive pregnant women, the preterm infant group with a gestational age between 34 and 37 weeks had a significantly lower GBS positive rate and a significantly higher level of anti-GBS capsular polysaccharide antibody compared with the preterm infant group with a gestational age of less than 34 weeks (P=0.013 and 0.001 respectively). A multivariate logistic regression analysis revealed that premature rupture of membranes time >18 hours and chorioamnionitis were independent risk factors for GBS colonization in preterm infants (OR=6.556 and 6.160 respectively; P<0.05).
Conclusions: GBS positive rate and anti-GBS capsular polysaccharide antibody level in preterm infants are correlated with gestational age. premature rupture of membranes time >18 hours and chorioamnionitis may increase the risk of GBS colonization in preterm infants.
目的: 探讨孕妇B族溶血性链球菌（GBS）定植及其分娩早产儿的GBS感染状况，评估早产儿GBS定植的危险因素。
方法: 采用前瞻性队列研究方法，纳入2017年1月至2018年1月分娩的859例早产孕妇作为研究对象。入院时采集孕妇阴道下段1/3和直肠拭子行GBS培养，其中515例行实时PCR GBS DNA检测。采集所纳入孕妇分娩的早产儿的口咽分泌物、胃液或血液进行GBS培养。取孕妇外周血及其分娩的早产儿脐血测定抗GBS荚膜多糖抗体水平。调查早产儿GBS感染情况和影响定植的围产因素。
结果: 859例孕妇阴道、直肠GBS培养阳性率为14.8%（127/859）。515例GBS DNA检测的阳性率为15.1%（78/515）。859例孕妇共分娩活产早产儿976例，其中43例（4.4%）GBS培养阳性；4例发生早发型GBS疾病，其中2例肺炎，2例早发型GBS败血症。127例GBS阳性孕妇分娩的127例早产儿中，34~ <37周早产儿组GBS阳性率明显低于 <34周早产儿组（P=0.013），抗GBS荚膜多糖抗体水平明显高于 <34周早产儿组（P=0.001）。多因素logistic回归分析显示胎膜早破>18 h和绒毛膜羊膜炎是早产儿GBS定植的独立危险因素（分别OR=6.556、6.160，均P < 0.05）。
结论: 早产儿GBS阳性率及抗GBS荚膜多糖抗体水平与胎龄相关。胎膜早破>18 h和绒毛膜羊膜炎可增加早产儿GBS定植的风险。