TriCore Reference Laboratories, Albuquerque, New Mexico, USA.
Department of Pathology and Laboratory Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
J Clin Microbiol. 2020 Dec 17;59(1). doi: 10.1128/JCM.01902-19.
Group B (GBS) can be found to colonize about 25% of all healthy, adult women and is the leading infectious cause of early neonatal morbidity and mortality in the United States. This study evaluated the clinical performance of PhenoMatrix (PM) chromogenic detection module (CDM) digital imaging software in detection of GBS from LIM broth plated on ChromID Strepto B chromogenic medium (ChromID) using the WASP automated processor. The performance of the PM CDM was compared to manual culture review of the digital images and molecular detection of GBS. ChromID alone had a sensitivity and specificity of 84.5% and 94.7%, respectively, after 48 h compared to nucleic acid amplification testing (NAAT). Compared to the composite reference for positivity, when PM CDM was used to detect GBS from ChromID, the sensitivity was 100%, with no true-positive GBS isolates missed by 48 h of incubation. Overall, evaluating all three methods for the detection of GBS, the sensitivities of NAAT, ChromID plus PM CDM at 48 h, and ChromID alone at 48 h were 96.8%, 95.5%, and 90.3%, respectively. The specificities of NAAT, ChromID plus PM CDM, and ChromID alone were 97.7%, 63.0%, and 95.4%, respectively. The sensitivity of ChromID in combination with the PM CDM was similar to the sensitivity of molecular detection. Further, the algorithm never called a culture negative that was determined to be positive by manual reading, and it identified an additional eight true positive specimens that were missed by manual digital image culture reading.
B 群链球菌（GBS）可在约 25%的所有健康成年女性中定植，是美国导致新生儿早期发病和死亡的主要感染性病因。本研究评估了 PhenoMatrix（PM）显色检测模块（CDM）数字成像软件在使用 WASP 自动处理器对 ChromID 链状 B 显色培养基上的 LIM 肉汤进行平板培养后检测 GBS 的临床性能。PM CDM 的性能与数字图像的人工培养评估和 GBS 的分子检测进行了比较。与核酸扩增检测（NAAT）相比，ChromID 在 48 小时时的敏感性和特异性分别为 84.5%和 94.7%。与阳性复合参考标准相比，当使用 PM CDM 从 ChromID 检测 GBS 时，在孵育 48 小时时，其敏感性为 100%，没有错过任何一个真正的 GBS 阳性分离株。总体而言，评估所有三种方法检测 GBS，NAAT、48 小时时的 ChromID 加 PM CDM 和单独 ChromID 的敏感性分别为 96.8%、95.5%和 90.3%。NAAT、ChromID 加 PM CDM 和单独 ChromID 的特异性分别为 97.7%、63.0%和 95.4%。ChromID 与 PM CDM 联合使用的敏感性与分子检测的敏感性相似。此外，该算法从未将人工阅读确定为阳性的培养物误判为阴性，并且还鉴定出了 8 份人工数字图像培养阅读遗漏的真正阳性标本。
