一种新型B群链球菌显色培养基在孕妇产前B群链球菌检测中的应用效果研究

A study on clinical application of a new group B streptococcus chromogenic medium for detection of group B streptococcus in maternal prenatal screening

目的通过与CDC推荐THB+BAP及质谱鉴定(MS)相结合的参考方法比对,评估一种新型B群链球菌显色肉汤(GBSB)在孕妇产前B群链球菌(GBS)检测中的应用效果。方法接种不同浓度的GBS标准株测定GBSB检测限,并用87株GBS临床分离株进行验证;接种干扰菌测定GBSB的杂菌抑制性。以THB+BAP+MS为对比方法,分别对702例临床孕妇拭子样本(378例阴道分泌物和324例肛周分泌物)同步进行了2种方法对比检测,分析二者检测结果差异。结果标准菌株ATCC12386测定GBSB的检测限为100 cfu/ml,在该检出限条件下共验证87株GBS临床株,其中85株GBSB检测为阳性,10株常见杂菌即使0.5麦氏单位也不干扰。以对比方法为参比,702例临床孕妇拭子样本GBSB检测的灵敏度、特异度、阳性预测值、阴性预测值均达到了93%~100%,Kappa分析二者的一致性较好。结论GBSB是一种更简单、方便、高效、低耗的GBS检测方法,具有较好临床推广应用价值。

Objective To explore a new type of group B Streptococcus chromogenic medium(GBSB)suitable for efficient enrichmentand identification of GBS in maternal prenatal screening,by comparing it with the reference method of combined inoculation into a selective Todd-Hewitt broth(THB)with subculture on blood agar plate(BAP)with MALDI-TOF MS identification.Methods The limit of detection and anti-interference capability of GBSB were determined with standard strains,validated by 87 clinical isolates identified as GBS by MALDI-TOF MS.The appearance of an orange pigment in GBSB was indicative of the presence of GBS.Direct inoculation into GBS broth was compared to the CDC recommended method for the detection of group B streptococci(GBS)in pregnant women with 702 clinical specimen which 378 vaginal swabs and 324 rectal swabs were included.The identification of ambiguous bacteria on sheep blood agar plates were determined by MALDI-TOF MS,and GBSB discolored cultures were sub-cultured for re-identification.The sensitivity,specificity,the positive predictive value and the negative predictive value were determined.Data was analyzed with Kappa analysis by use of SPSS 18.0.Results The limit of GBS Broth was 100 cfu/ml for GBS detection,validated by 85 GBS strains isolated from clinical specimen.There was no interference by non GBS strains.Among the 702 clinical specimen from pregnant women,the sensitivity,specificity,the positive predictive value and the negative predictive value of the GBSB method was 93%to 100%,which was well consistent with the CDC recommended method by Kappa analysis.Conclusion As a more accurate,easier,and cheaper method of identification in maternal prenatal screening,GBS broth has a greater value of clinical application.