Kassim Ali, Pflüger Valentin, Premji Zul, Daubenberger Claudia, Revathi Gunturu
Aga Khan University Hospital, Nairobi, Kenya.
Mabritec AG, Riehen, Switzerland.
BMC Microbiol. 2017 May 25;17(1):128. doi: 10.1186/s12866-017-1037-z.
MALDI-TOF MS is an analytical method that has recently become integral in the identification of microorganisms in clinical laboratories. It relies on databases that majorly employ pattern recognition or fingerprinting. Biomarker based databases have also been developed and there is optimism that these may be superior to pattern recognition based databases. This study compared the performance of ribosomal biomarker based MALDI-TOF MS and conventional methods in the identification of selected bacteria and yeast.
The study was a cross sectional study identifying clinically relevant bacteria and yeast isolated from varied clinical specimens submitted to a clinical laboratory. The identification of bacteria using conventional Vitek 2™ automated system, serotyping and MALDI-TOF MS was performed as per standard operating procedures. Comparison of sensitivities were then carried out using Pearson Chi-Square test and p-value of <0.05 was considered statistically significant. Secondary outcomes analyzed included the major and minor error rates.
Of the 383 isolates MALDI-TOF MS and conventional methods identified 97.6 and 95.7% (p = 0.231) to the genus level and 97.4 and 88.0% (p = 0.000) to the species level respectively. Biomarker based MALDI-TOF MS was significantly superior to Vitek 2™ in the identification of Gram negative bacteria and Gram positive bacteria to the species level. For the Gram positive bacteria, significant difference was observed in the identification of Coagulase negative Staphylococci (p = 0.000) and Enterococcus (p = 0.008). Significant difference was also observed between serotyping and MALDI-TOF MS (p = 0.005) and this was attributed to the lack of identification of Shigella species by MALDI-TOF MS. There was no significant difference observed in the identification of yeast however some species of Candida were unidentified by MALDI-TOF MS.
Biomarker based MALDI-TOF MS had good performance in a clinical laboratory setting with high sensitivities in the identification of clinically relevant microorganisms.
基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）是一种分析方法，最近已成为临床实验室微生物鉴定中不可或缺的手段。它依赖于主要采用模式识别或指纹识别的数据库。基于生物标志物的数据库也已开发出来，人们乐观地认为这些数据库可能优于基于模式识别的数据库。本研究比较了基于核糖体生物标志物的MALDI-TOF MS和传统方法在鉴定选定细菌和酵母菌方面的性能。
本研究为横断面研究，旨在鉴定从提交至临床实验室的各种临床标本中分离出的具有临床相关性的细菌和酵母菌。按照标准操作程序，使用传统的Vitek 2™自动化系统、血清分型和MALDI-TOF MS对细菌进行鉴定。然后使用Pearson卡方检验进行敏感性比较，p值<0.05被认为具有统计学意义。分析的次要结果包括主要和次要错误率。
在383株分离株中，MALDI-TOF MS和传统方法在属水平上的鉴定率分别为97.6%和95.7%（p = 0.231），在种水平上的鉴定率分别为97.4%和88.0%（p = 0.000）。基于生物标志物的MALDI-TOF MS在将革兰氏阴性菌和革兰氏阳性菌鉴定到种水平方面明显优于Vitek 2™。对于革兰氏阳性菌，在凝固酶阴性葡萄球菌（p = 0.000）和肠球菌（p = 0.008）的鉴定中观察到显著差异。在血清分型和MALDI-TOF MS之间也观察到显著差异（p = 0.005），这归因于MALDI-TOF MS未能鉴定出志贺氏菌属。在酵母菌的鉴定中未观察到显著差异，然而MALDI-TOF MS未能鉴定出某些念珠菌属。
基于生物标志物的MALDI-TOF MS在临床实验室环境中表现良好，在鉴定具有临床相关性的微生物方面具有较高的敏感性。
