Background

Molecular genetics has risen in both output and affordability to become the gold standard in diagnosis, however it is not yet available for most routine clinical microbiology due to cost and the level of skill it requires. Matrix assisted laser desorption/ionisation – time of flight mass spectrometry (MALDI-TOF MS) approaches may be useful in bridging the gap between low-resolution phenotypic methods and bulky genotypic methods in the goal of epidemiological source-typing of microbes. Burkholderia has been shown to be identifiable at the subspecies level using MALDI-TOF MS. There have not yet been studies assessing the ability of MALDI-TOF MS to source-type Burkholderia contaminans isolates into epidemiologically relevant outbreak clusters.

Methods

55 well-characterised B. contaminans isolates were used to create a panel for analysis of MALDI-TOF MS biomarker peaks and their relation to outbreak strains, location, source, patient, diagnosis and isolate genetics. Unsupervised clustering was performed and classification models were generated using biostatistical analysis software.

Results

B. contaminans spectra derived from MALDI-TOF MS were of sufficiently high resolution to identify 100% of isolates. Unsupervised clustering methods showed poor evidence of spectra clustering by all characteristics measured. Classification algorithms were discriminatory, with Genetic Algorithm models showing 100% recognition capability for all outbreaks, the pulsed-field gel electrophoresis (PFGE) typeability model, and 96.63% recognition for the location model. A consistent peak at m/z of approximately 6943 was identified in all non-typeable strains but in none of the typeable strains.

Conclusions

MALDI-TOF MS successfully discriminates B. contaminans isolates into clonal, epidemiological clusters, and can recognise isolates non-typeable by PFGE. Further work should investigate this capability, and include peptide studies and genomic sequencing to identify individual proteins or genes responsible for this non-typeablity, particularly at the peak weight identified.

中文翻译：

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探索 MALDI-TOF MS 在检测伯克霍尔德菌克隆暴发中的价值

背景

分子遗传学在产量和可负担性方面都有所提高，已成为诊断的金标准，但由于成本和所需的技能水平，它尚未用于大多数常规临床微生物学。基质辅助激光解吸/电离 - 飞行时间质谱 (MALDI-TOF MS) 方法可能有助于弥合低分辨率表型方法和庞大的基因型方法之间的差距，以实现微生物流行病学来源分型的目标。使用 MALDI-TOF MS 已证明伯克霍尔德菌在亚种水平上是可识别的。尚未有研究评估 MALDI-TOF MS 将伯克霍尔德氏菌污染分离株转化为流行病学相关暴发集群的能力。

方法

55 个充分表征的B. contaminans分离株用于创建一个面板，用于分析 MALDI-TOF MS 生物标志物峰及其与暴发菌株、位置、来源、患者、诊断和分离遗传学的关系。使用生物统计分析软件进行无监督聚类并生成分类模型。

结果

源自 MALDI-TOF MS 的B. 污染物光谱具有足够高的分辨率以识别 100% 的分离物。无监督聚类方法显示所有测量特征的光谱聚类证据不足。分类算法具有区分性，遗传算法模型显示对所有暴发的 100% 识别能力，脉冲场凝胶电泳 (PFGE) 可分型模型和定位模型的 96.63% 识别能力。在所有不可分型菌株中均发现m/z约为 6943的一致峰，但在可分型菌株中均未发现。

结论

MALDI-TOF MS 成功地将B. contaminans分离株区分为克隆的流行病学簇，并且可以识别无法通过 PFGE 分型的分离株。进一步的工作应该研究这种能力，包括肽研究和基因组测序，以识别导致这种不可分型性的单个蛋白质或基因，特别是在确定的峰值重量时。