不同培养基及B族链球菌增菌肉汤检测B族链球菌效果评价

Evaluation on the efficiency of different media and GBS enrichment broth for GBS detection

目的：通过分析B族链球菌（ GBS）检测的阳性检出率和平板选择性能来评价GBS筛查培养基、哥伦比亚血琼脂培养基和GBS增菌肉汤检测结果的可靠性和临床应用的可行性。方法收集妊娠晚期35～37周孕妇阴道下端及肛周样本242例、中段尿样本15例，同时直接接种及经GBS增菌肉汤增菌后接种哥伦比亚血平板和GBS筛查平板，观察各培养基上GBS的生长情况。结果直接接种后分别培养24 h和48 h，哥伦比亚血琼脂培养基GBS的检出率均为7．39％（19／257）；而GBS筛查培养基的检出率为24 h 5．45％（14／257）、48 h 7．39％（19／257）。经GBS增菌肉汤增菌后，无论培养时间是24 h还是48 h，哥伦比亚血琼脂培养基GBS的检出率均为9．73％（25／257）；GBS筛查培养基的检出率均为8．95％（23／257）。与直接接种相比，选择性增菌后GBS的检出率明显升高；2种培养基GBS的检出率差异无统计学意义（P＞0．05）。结论临床样本先经GBS增菌肉汤18～24 h增菌后再接种至GBS筛查培养基或哥伦比亚血琼脂培养基，24 h即可观察生长结果，GBS 菌落易于辨认且提高了阳性检出率。

Objective To evaluate the reliability of Group B Streptococcus （ GBS ） screening medium, Colombia blood agar medium and GBS enrichment broth detection results and investigate the viability of clinical application by analyzing the positive rate of GBS and the performance of selective plates.Methods A total of 242 samples from distal vaginal segment and around crissum and 15 midstream urine samples were collected among 35-37-week pregnant women. The samples were inoculated directly and with one more step of GBS enrichment broth on Colombia blood agar and GBS screening media, respectively, and the growth of GBS in the 2 kinds of media was observed.Results As for inoculating directly, the detection rates of GBS in Colombia blood agar medium for 24 h and 48 h were 7.39%（19/257） , and the 24 h and 48 h detection rates of GBS in GBS screening medium were 5.45%（ 14/257 ） and 7.39%（ 19/257 ） , respectively.As for inoculating with one more step of GBS enrichment broth, for neither 24 h nor 48 h, the detection rate of GBS in Colombia blood agar medium was 9.73%（25/257）, and the detection rate in GBS screening medium was 8.95%（23/257）, both of which had an evident increasing comparing with the former one.There was no statistical significance for the detection rate between the 2 kinds of media （P〉0.05）.Conclusions By enriching 18 h-24 h in GBS enrichment broth, followed by inoculating in GBS screening medium or Colombia blood agar medium, the growth of GBS from clinical samples in media could be observed just after 24 h, and this method has simple recognition ability for GBS and can improve GBS positive detection rate.