Lasch Peter, Fleige Carola, Stämmler Maren, Layer Franziska, Nübel Ulrich, Witte Wolfgang, Werner Guido
Robert Koch Institute, Division Proteomics and Spectroscopy (ZBS 6), Berlin, Germany.
Robert Koch Institute, Division Nosocomial Pathogens and Antimicrobial Resistances (FG13), Wernigerode Branch, Germany.
J Microbiol Methods. 2014 May;100:58-69. doi: 10.1016/j.mimet.2014.02.015. Epub 2014 Mar 12.
MALDI-TOF mass spectrometry (MALDI-TOF MS) is increasingly used as a reliable technique for species identification of bacterial pathogens. In this study we investigated the question of whether MALDI-TOF MS can be used for accurate sub-differentiation of strains and isolates of two important nosocomial pathogens Enterococcus faecium and Staphylococcus aureus. For this purpose, a selection of 112 pre-characterized E. faecium isolates (clonal complexes CC2, CC5, CC9, CC17, CC22, CC25, CC26, CC92 altogether 52 multilocus sequence types) and 59 diverse S. aureus isolates (mostly methicillin resistant; CC5, CC8, CC22, CC30, CC45, CC398) were studied using a combination of MALDI-TOF MS and advanced methods of spectral data analysis. The strategy of MS data evaluation included manual peak inspection on the basis of pseudo gel views, unsupervised hierarchical cluster analysis and supervised artificial neural network (ANN) analysis. We were capable of differentiating patterns of hospital-associated E. faecium isolates (CC17) from other strains of E. faecium with 87% accuracy, but failed to identify lineage-specific biomarker peaks. For S. aureus pattern analyses we were able to confirm a number of signals described in previous studies, but often failed to identify biomarkers that would allow a consistent and reliable identification of phylogenetic lineages, clonal complexes or sequence types. Hence, the discriminatory power of MALDI-TOF MS was found to be insufficient for reliably sub-differentiating E. faecium and S. aureus isolates to the level of distinct clones or clonal complexes, such as assessed by MLST. Further, a comparison between peak patterns of susceptible and resistant isolates did not identify statistically relevant marker peaks linked to glycopeptide resistance determinants (vanA, vanB) in E. faecium, or the methicillin resistance determinant (mecA) in S. aureus.
基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）越来越多地被用作鉴定细菌病原体种类的可靠技术。在本研究中，我们调查了MALDI-TOF MS是否可用于准确区分两种重要的医院病原体粪肠球菌和金黄色葡萄球菌的菌株和分离株的问题。为此，我们使用MALDI-TOF MS和先进的光谱数据分析方法，对112株预先鉴定的粪肠球菌分离株（克隆复合体CC2、CC5、CC9、CC17、CC22、CC25、CC26、CC92，共52个多位点序列类型）和59株不同的金黄色葡萄球菌分离株（大多耐甲氧西林；CC5、CC8、CC22、CC30、CC45、CC398）进行了研究。MS数据评估策略包括基于伪凝胶视图的手动峰检查、无监督层次聚类分析和有监督人工神经网络（ANN）分析。我们能够以87%的准确率区分医院相关粪肠球菌分离株（CC17）与其他粪肠球菌菌株的模式，但未能识别谱系特异性生物标志物峰。对于金黄色葡萄球菌模式分析，我们能够确认先前研究中描述的一些信号，但经常未能识别能够一致且可靠地鉴定系统发育谱系、克隆复合体或序列类型的生物标志物。因此，发现MALDI-TOF MS的鉴别能力不足以将粪肠球菌和金黄色葡萄球菌分离株可靠地区分到不同克隆或克隆复合体的水平，如通过多位点序列分型（MLST）评估的那样。此外，敏感和耐药分离株的峰模式比较未发现与粪肠球菌中的糖肽抗性决定因素（vanA、vanB）或金黄色葡萄球菌中的甲氧西林抗性决定因素（mecA）相关的统计学上相关的标记峰。
