Leibniz Institute of Photonic Technology , Jena, Germany.
Friedrich Loeffler Institute of Medical Microbiology, Greifswald University Hospital , Greifswald, Germany.
Anal Chem. 2018 Feb 6;90(3):1811-1818. doi: 10.1021/acs.analchem.7b03800. Epub 2018 Jan 11.
Resistant bacteria are spreading worldwide, which makes fast antibiotic susceptibility testing and determination of the minimal inhibitory concentration (MIC) urgently necessary to select appropriate antibiotic therapy in time and, by this, improve patient's outcome and, at the same time, avoid inappropriate treatment as well as the unnecessary use of broad spectrum antibiotics that would foster further spread of resistant bacteria. Here, a simple and fast Raman spectroscopy-based procedure is introduced to identify antimicrobial susceptibilities and determine the MIC within only 2 h total analysis, marking a huge time savings compared to established phenotypic methods nowadays used in diagnostics. Sample preparation is fast and easy as well as comparable to currently established tests. The use of a dielectrophoresis chip allows automated collection of the bacteria in a micron-sized region for high-quality Raman measurement directly from bacterial suspensions. The new Raman spectroscopic MIC test was validated with 13 clinical E. coli isolates that show a broad range of ciprofloxacin resistance levels and were collected from patients with blood-stream infection. Micro-Raman spectroscopy was able to detect ciprofloxacin-induced changes in E. coli after only 90 min interaction time. Principal component analysis as well as a simple computed ratio of the Raman marker bands at 1458 and 1485 cm show a clear concentration-dependent effect. The MIC values determined with the new Raman method are in good agreement with MICs obtained by reference methods (broth microdilution, Vitek-2, E-test) and can be used to provide a classification as sensitive, intermediate, or resistant using the clinical breakpoints provided by EUCAST.
耐药菌在全球范围内传播，这使得快速抗生素药敏试验和最小抑菌浓度 (MIC) 的测定变得非常必要，以便及时选择合适的抗生素治疗，从而改善患者的预后，同时避免不适当的治疗和不必要的广谱抗生素的使用，这会助长耐药菌的进一步传播。这里，引入了一种简单快速的基于拉曼光谱的方法，用于在总共 2 小时的分析时间内鉴定抗菌药物敏感性并确定 MIC，与当今诊断中使用的经典表型方法相比，这大大节省了时间。样品制备既快速又简单，与目前已建立的测试方法相当。使用介电泳芯片可以自动将细菌收集到微米大小的区域，以便直接从细菌悬浮液中进行高质量的拉曼测量。新的拉曼光谱 MIC 测试用 13 株临床分离的大肠杆菌进行了验证，这些大肠杆菌对环丙沙星的耐药水平广泛，来自血流感染患者。微拉曼光谱仅在 90 分钟的相互作用时间后就能检测到环丙沙星对大肠杆菌的诱导变化。主成分分析以及对拉曼标记带 1458 和 1485 cm 处的简单计算比值的分析显示出明显的浓度依赖性效应。用新的拉曼方法确定的 MIC 值与参考方法（肉汤微量稀释法、Vitek-2、E-试验）获得的 MIC 值非常吻合，并且可以用于根据 EUCAST 提供的临床断点将其分类为敏感、中介或耐药。
