BACKGROUND The application of matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS) to microbial identification has allowed the development of rapid methods for identification of microorganisms directly in positive, blood cultures (BCs). These methods can yield accurate results for monomicrobial BCs, but often fail to identify multiple microorganisms in polymicrobial BCs. The present study was aimed at establishing a rapid and simple method for identification of bacteria and yeast in polymicrobial BCs from patients with bloodstream infection. RESULTS The rapid method herein proposed is based on short-term culture in liquid media allowing selective growth of microorganisms recovered from polymicrobial BCs, followed by rapid identification by MALDI-TOF MS. To evaluate the accuracy of this method, 56 polymicrobial BCs were comparatively analyzed with the rapid and routine methods. The results showed concordant identification for both microbial species in 43/50 (86%) BCs containing two different microorganisms, and for two microbial species in six BCs containing more than two different species. Overall, 102/119 (85.7%) microorganisms were concordantly identified by the rapid and routine methods using a cut-off value of 1.700 for valid identification. The mean time to identification after BC positivity was about 4.2 h for streptococci/enterococci, 8.7 h for staphylococci, 11.1 h for Gram-negative bacteria, and 14.4 h for yeast, allowing a significant time saving compared to the routine method. CONCLUSIONS The proposed method allowed rapid and reliable microbial identification in polymicrobial BCs, and could provide clinicians with timely, useful information to streamline empirical antimicrobial therapy in critically ill patients.

中文翻译：

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一种基于培养物的新方法，可通过MALDI-TOF MS快速鉴定微生物血液培养物中的微生物。

背景技术将基质辅助激光解吸/电离飞行时间（MALDI-TOF）质谱（MS）应用于微生物鉴定已经允许开发用于直接在阳性血液培养物（BCs）中鉴定微生物的快速方法。这些方法可以对单微生物BCs产生准确的结果，但通常无法鉴定多微生物BCs中的多种微生物。本研究旨在建立一种快速，简单的方法来鉴定来自血液感染患者的多菌种BCs中的细菌和酵母菌。结果本文提出的快速方法是基于在液体培养基中的短期培养，允许从微生物BCs中回收的微生物选择性生长，然后通过MALDI-TOF MS快速鉴定。要评估此方法的准确性，使用快速和常规方法对56株细菌性BC进行了比较分析。结果表明，在包含两种不同微生物的43/50（86％）BC中，对两种微生物菌种具有一致的鉴定；在包含两种以上不同菌种的6种BC中，对于两种微生物菌种具有一致的鉴定。总体而言，通过快速和常规方法一致地鉴定了102/119（85.7％）个微生物，使用有效分界值为1.700进行了鉴定。BC阳性后鉴定的平均时间为链球菌/肠球菌约4.2 h，葡萄球菌8.7 h，革兰氏阴性菌11.1 h，酵母14.4 h，与常规方法相比，可节省大量时间。结论所提出的方法可以快速，可靠地鉴定多菌种BC中的微生物，并可以为临床医生提供及时，