Centre for Infectious Diseases and Microbiology Laboratory Services, NSW Health Pathology, Westmead Hospital, Westmead NSW, Australia.
Centre for Infectious Diseases and Microbiology Laboratory Services, NSW Health Pathology, Westmead Hospital, Westmead NSW, Australia.
Clin Microbiol Infect. 2017 Dec;23(12):948-951. doi: 10.1016/j.cmi.2017.04.022. Epub 2017 May 6.
We adapted the BD Max GBS assay, an automated platform for the detection of Group B streptococcus (GBS) DNA in vaginal-rectal swab specimens after LIM broth enrichment, to directly detect GBS in specimens collected using cellular foam swabs in Amies liquid medium. We compared the BD Max GBS assay performance to that of enriched culture and the BD GeneOhm StrepB assay.
Seventy-two reference vaginal-rectal specimens were employed to determine the limit of GBS detection and the preferred test volume for direct detection of GBS. A total of 304 clinical specimens were then tested by the optimized BD Max GBS assay, both by direct testing and following broth enrichment.
The limit of GBS detection was 75 CFU/mL and the preferred test volume was 100 μL. Of 304 clinical specimens tested, GBS was detected in 62 specimens by enriched culture (20.4%); 61 of these yielded GBS by the BD Max GBS assay when performed directly from the liquid swab (sensitivity 98.4%). All 242 culture-negative specimens also yielded negative results by the BD Max GBS assay (specificity 100%). When this assay was performed following broth enrichment, GBS was detected in all 62 culture-positive specimens (100% sensitivity). The sensitivity and specificity of the BD GeneOhm StrepB assay was 90.3% and 99%, respectively.
The BD Max GBS assay is highly sensitive, requires minimal technical skill with <2 min required to set-up, and results are available in under 80 min (versus 24-48 h for culture). It is configured for 'on demand' testing and vaginal-rectal specimens can be rapidly screened for GBS without the need for enrichment. The results obtained in this study demonstrate that rapid GBS screening using the BD Max GBS assay at the time of delivery is a viable alternative to the current recommended screening at 35-37 weeks of gestation with pre-enrichment testing methods.
我们对 BD Max GBS 检测法进行了改良，该方法采用 LIM 肉汤增菌后，对阴道直肠拭子标本中的 B 型链球菌（GBS）DNA 进行自动化检测，使其可直接检测 Amies 液体培养基中细胞泡沫拭子采集的标本中的 GBS。我们比较了 BD Max GBS 检测法与增菌培养和 BD GeneOhm StrepB 检测法的性能。
采用 72 份参考阴道直肠拭子标本确定 GBS 的检测下限和直接检测 GBS 的最佳检测体积。然后对 304 份临床标本进行优化后的 BD Max GBS 检测法检测，既直接检测，也进行肉汤增菌后检测。
GBS 的检测下限为 75 CFU/mL，最佳检测体积为 100 μL。在 304 份临床标本中，62 份标本经增菌培养检出 GBS（20.4%）；61 份直接从液体拭子中用 BD Max GBS 检测法检测到 GBS（敏感性 98.4%）。242 份培养阴性的标本也全部用 BD Max GBS 检测法检测为阴性（特异性 100%）。当该检测法进行肉汤增菌后检测时，所有 62 份培养阳性标本均检出 GBS（敏感性 100%）。BD GeneOhm StrepB 检测法的敏感性和特异性分别为 90.3%和 99%。
BD Max GBS 检测法高度敏感，操作技术要求低，设置时间不到 2 分钟，结果在 80 分钟内（培养法需要 24-48 小时）得出。它可随时进行检测，阴道直肠标本可无需增菌而快速筛查 GBS。本研究的结果表明，在分娩时使用 BD Max GBS 检测法快速筛查 GBS，是替代目前推荐的在 35-37 孕周进行的、有预增菌检测方法的筛查方法的一种可行方法。
