Aupaix Antoine, Verroken Alexia, Rodriguez-Villalobos Hector
Department of Microbiology, Cliniques Universitaires Saint-Luc, Catholic University of Louvain, Brussels, Belgium.
J Clin Microbiol. 2025 Jan 31;63(1):e0122224. doi: 10.1128/jcm.01222-24. Epub 2024 Dec 18.
This study aimed to evaluate a new protocol of the bile solubility test performed directly on the blood from positive blood culture bottles to identify rapidly. Seventy-five positive blood cultures (PBC) showing Gram-positive cocci in pairs or chains on Gram stain, including 32 isolates and three reference American Type Culture Collection (ATCC) isolates were included to evaluate the performance of a modified bile solubility test (MBST). One milliliter of blood from the PBC bottle was mixed with 0.5 mL of 10% desoxycholate or a saline solution. Both suspensions were analyzed after 10 min of incubation through a Gram stain to detect solubilization. This technique was compared with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry identification, performed on PBC following extraction or on colonies after short or standard incubation, and the optochin susceptibility test on colonies. The capsular serotypes were determined for all , and the Belgian National Reference Center confirmed the identification. All 32 clinical isolates and the ATCC isolate of were solubilized on the desoxycholate-treated slides, while the other species tested remained visually unchanged on both, the test and control slides. The MBST test demonstrated a 100% sensitivity and specificity with a mean turnaround time (TAT) of just 39 min, making it 14 h and 56 min faster than the optochin susceptibility test. This rapid variant of the bile solubility test appears to be a reliable method to identify directly from positive blood culture bottles, with a TAT of 39 min. It is a cost-effective, easy-to-perform, and time-efficient technique. Negative results should be interpreted cautiously, as they may result from mixed infections with and other Gram-positive cocci.
本研究旨在评估一种直接对阳性血培养瓶中的血液进行胆汁溶解试验的新方案，以便快速鉴定。纳入了75份革兰氏染色显示成对或成链革兰氏阳性球菌的阳性血培养物（PBC），包括32株临床分离株和3株美国典型培养物保藏中心（ATCC）参考分离株，以评估改良胆汁溶解试验（MBST）的性能。将1毫升来自PBC瓶的血液与0.5毫升10%去氧胆酸盐或盐溶液混合。孵育10分钟后，通过革兰氏染色分析两种悬液以检测溶解情况。将该技术与基质辅助激光解吸/电离飞行时间质谱鉴定进行比较，后者在PBC提取后或短时间或标准孵育后的菌落上进行，以及对菌落进行奥普托欣敏感性试验。确定了所有菌株的荚膜血清型，比利时国家参考中心确认了鉴定结果。所有32株临床分离株和肺炎链球菌的ATCC分离株在经去氧胆酸盐处理的载玻片上均被溶解，而其他测试菌种在试验和对照载玻片上均保持外观不变。MBST试验的敏感性和特异性均为100%，平均周转时间（TAT）仅为39分钟，比奥普托欣敏感性试验快14小时56分钟。这种胆汁溶解试验的快速变体似乎是一种从阳性血培养瓶中直接鉴定肺炎链球菌的可靠方法，TAT为39分钟。它是一种经济高效、易于操作且省时的技术。阴性结果应谨慎解释，因为它们可能是由肺炎链球菌与其他革兰氏阳性球菌混合感染导致的。
