Background/purpose

Early identification of pathogens causing bloodstream infection (BSI) is critical for prompt administration of appropriate antimicrobial therapy.

Methods

We used an in-house saponin-based extraction method to evaluate the performance of Bruker Biotyper MALDI-TOF MS system (MALDI Biotyper) for bacterial and fungal identification in 2013 positively-flagged VersaTREK blood culture bottles.

Results

A total of 180 monomicrobial and 23 polymicrobial positive blood cultures were investigated. Among monomicrobial positive blood cultures, the MALDI Biotyper recognized 90.6% and 81.7% of organisms directly from the flagged blood culture bottles to the genus and species levels, respectively. The MALDI Biotyper also correctly characterized one of the polymicrobial organisms to the species level in 20 (87%) bottles and to the genus level in 21 (91.3%) bottles. The overall identification rate using our protocol was 90.6% (184/203) and 82.3% (167/203) for genus and species levels, respectively. Identification accuracy was higher for Gram-positive than Gram-negative organisms and was the lowest for yeasts. Score values of identification were ≥1.500 for 200 (98.5%) bottles, ≥1.700 for 195 (96.1%) bottles and ≥2.000 for 182 (89.7%) bottles. Moreover, 83.5% and 92% of the isolates were identified precisely to species and genus level with the lower cutoff score of 1.500. Using our protocol also helped identifying BSI pathogens 18–24 h earlier compared to the sub-cultured colonies.

Conclusion

Using Bruker MALDI Biotyper for identification of isolates directly from positive VersaTREK blood culture bottles, our in-house saponin-based protocol provided a more rapid turn-around time for correct identification of BSI pathogens than the conventional methods.

中文翻译：

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基于内部皂苷的提取方法在 Bruker Biotyper 基质辅助激光解吸/电离飞行时间质谱系统中的适用性，用于鉴定阳性标记的儿科 VersaTREK 血培养中的细菌和真菌物种

背景/目的

及早识别引起血流感染 (BSI) 的病原体对于及时给予适当的抗菌治疗至关重要。

方法

我们使用内部基于皂苷的提取方法来评估 Bruker Biotyper MALDI-TOF MS 系统 (MALDI Biotyper) 在 2013 年阳性标记 VersaTREK 血培养瓶中细菌和真菌鉴定的性能。

结果

总共研究了 180 个单一微生物和 23 个多微生物阳性血培养物。在单一微生物阳性血培养物中，MALDI Biotyper 分别识别了 90.6% 和 81.7% 的微生物，它们分别来自标记的血培养瓶中的属和种水平。MALDI Biotyper 还在 20 个 (87%) 瓶中的物种水平和 21 个 (91.3%) 瓶中的属水平上正确表征了一种多微生物有机体。使用我们的协议的总体识别率在属和种水平上分别为 90.6% (184/203) 和 82.3% (167/203)。革兰氏阳性菌的鉴定准确度高于革兰氏阴性菌，而酵母菌的鉴别准确率最低。200 (98.5%) 瓶的鉴定分值≥1.500，195 (96.1%) 瓶≥1.700，182 (89.7%) 瓶≥2.000。此外，83。5% 和 92% 的分离株被精确鉴定到种和属水平，下界分数为 1.500。与亚培养菌落相比，使用我们的协议还有助于提前 18-24 小时识别 BSI 病原体。

结论

使用 Bruker MALDI Biotyper 直接从阳性 VersaTREK 血培养瓶中鉴定分离株，我们内部基于皂苷的方案为正确鉴定 BSI 病原体提供了比传统方法更快的周转时间。