Background The most successful application of mass spectrometry (MS) in laboratory medicine is identification (ID) of microorganisms using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) in blood stream infection. We describe MALDI-TOF MS-based bacterial ID with particular emphasis on the methods so far developed to directly identify microorganisms from positive blood culture bottles with MALDI-TOF MS including our own protocols. We touch upon the increasing roles of Liquid chromatography (LC) coupled with tandem mass spectrometry (MS/MS) as well. Main body Because blood culture bottles contain a variety of nonbacterial proteins that may interfere with analysis and interpretation, appropriate pretreatments are prerequisites for successful ID. Pretreatments include purification of bacterial pellets and short-term subcultures to form microcolonies prior to MALDI-TOF MS analysis. Three commercial protocols are currently available: the Sepsityper® kit (Bruker Daltonics), the Vitek MS blood culture kit (bioMerieux, Inc.), and the rapid BACpro® II kit (Nittobo Medical Co., Tokyo). Because these commercially available kits are costly and bacterial ID rates using these kits are not satisfactory, particularly for Gram-positive bacteria, various home-brew protocols have been developed: 1. Stepwise differential sedimentation of blood cells and microorganisms, 2. Combination of centrifugation and lysis procedures, 3. Lysis-vacuum filtration, and 4. Centrifugation and membrane filtration technique (CMFT). We prospectively evaluated the performance of this CMFT protocol compared with that of Sepsityper® using 170 monomicrobial positive blood cultures. Although preliminary, the performance of the CMFT was significantly better than that of Sepsityper®, particularly for Gram-positive isolates. MALDI-TOF MS-based testing of polymicrobial blood specimens, however, is still challenging. Also, its contribution to assessment of susceptibility and resistance to antibiotics is still limited. For this purpose, liquid chromatography (LC) coupled with tandem mass spectrometry (MS/MS) should be more useful because this approach can identify as many as several thousand peptide sequences. Conclusion MALDI-TOF MS is now an essential tool for rapid bacterial ID of pathogens that cause blood stream infection. For the purpose of assessment of susceptibility and resistance to antibiotics of the pathogens, the roles of liquid chromatography (LC) coupled with tandem mass spectrometry (MS/MS) will increase in the future.

中文翻译：

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基于质谱的血流感染微生物检测。

背景 质谱 (MS) 在检验医学中最成功的应用是使用基质辅助激光解吸电离飞行时间质谱 (MALDI-TOF MS) 在血流感染中鉴定 (ID) 微生物。我们描述了基于 MALDI-TOF MS 的细菌 ID，特别强调了迄​​今为止开发的使用 MALDI-TOF MS 直接从阳性血培养瓶中识别微生物的方法，包括我们自己的协议。我们还谈到了液相色谱 (LC) 与串联质谱 (MS/MS) 相结合的日益重要的作用。主体 由于血培养瓶中含有多种可能干扰分析和解释的非细菌蛋白，因此适当的预处理是成功鉴定的先决条件。预处理包括在 MALDI-TOF MS 分析之前纯化细菌颗粒和短期传代培养以形成微菌落。目前提供三种商业方案：Sepsityper® 试剂盒（Bruker Daltonics）、Vitek MS 血液培养试剂盒（bioMerieux, Inc.）和快速 BACpro® II 试剂盒（Nittobo Medical Co., Tokyo）。由于这些市售试剂盒价格昂贵，并且使用这些试剂盒的细菌鉴定率不令人满意，特别是对于革兰氏阳性菌，因此开发了各种自制方案：1. 血细胞和微生物的逐步差异沉降，2. 离心组合和裂解程序， 3. 裂解-真空过滤，和 4. 离心和膜过滤技术 (CMFT)。我们使用 170 个单微生物阳性血培养物前瞻性地评估了该 CMFT 方案与 Sepsityper® 方案的性能。虽然是初步的，但 CMFT 的性能明显优于 Sepsityper®，特别是对于革兰氏阳性分离物。然而，基于 MALDI-TOF MS 的多微生物血液样本测试仍然具有挑战性。此外，它对评估抗生素敏感性和耐药性的贡献仍然有限。为此，液相色谱 (LC) 与串联质谱 (MS/MS) 相结合应该更有用，因为这种方法可以识别多达数千个肽序列。结论 MALDI-TOF MS 现在是快速细菌识别引起血流感染的病原体的重要工具。