Background

Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS), commonly used for microorganism identification, can also be applied for the detection of carbapenemase-producing bacteria by the evaluation of carbapenem hydrolysis. Since KPC- and NDM-producing bacteria are related to high mortality rates, diagnostic assays for its detection are essential. The aim of this study was to develop and evaluate a method to establish a quantitative measure (hydrolysis index - HI) to detect meropenem hydrolysis by MLADI-TOF MS.

Methods

bla_KPC and bla_NDM positive and negative Klebsiella pneumoniae isolates and Escherichia coli ATCC 25922 (control) were incubated in a meropenem solution for 2 h. Protein extraction from these suspensions were submitted to MALDI-TOF MS analysis. The intensity of peaks at 384 m/z and 379 m/z of each isolate were used to establish the HI as follows: HI = (Peak intensity_{384 Test} / Peak intensity_{379 Test}) / (Peak intensity_{384 Control} / Peak intensity_{379 Control}). Receiver Operating Characteristic curve was used to determine a cutoff value to differentiate carbapenemase-producing from carbapenemase non-producing bacteria.

Results

As all carbapenemase-producing K. pneumoniae presented HI ≤0.55 and all carbapenemase non-producing isolates presented a HI ≥0.57, the index of 0.56 was established as a cutoff value to differentiate carbapenemase (KPC and NDM) producing and non-producing bacteria.

中文翻译：

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建立美罗培南水解定量指标用于MALDI-TOF MS检测产KPC和NDM菌

背景

基质辅助激光解吸电离飞行时间质谱 (MALDI-TOF MS) 常用于微生物鉴定，也可用于通过评价碳青霉烯水解来检测产碳青霉烯酶的细菌。由于产生 KPC 和 NDM 的细菌与高死亡率有关，因此对其检测的诊断分析是必不可少的。本研究的目的是开发和评估一种建立定量测量（水解指数 - HI）的方法，以通过 MLADI-TOF MS 检测美罗培南水解。

方法

bla _KPC和bla _NDM阳性和阴性肺炎克雷伯菌分离株和大肠杆菌ATCC 25922（对照）在美罗培南溶液中孵育 2 小时。从这些悬浮液中提取的蛋白质进行 MALDI-TOF MS 分析。使用每个分离株的384  m / z和 379 m/z 处的峰强度来确定 HI，如下所示：HI =（峰强度_{384 测试}/峰强度_{379 测试}）/（峰强度_{384 对照}/峰强度_{379 对照）}）。接受者操作特征曲线用于确定区分产碳青霉烯酶细菌和不产碳青霉烯酶细菌的临界值。

结果

由于所有产碳青霉烯酶肺炎克雷伯菌的HI ≤ 0.55，所有不产碳青霉烯酶的分离株的 HI ≥ 0.57，因此建立指数 0.56 作为区分产碳青霉烯酶（KPC 和 NDM）细菌和非产细菌的临界值。