Instant screening and verification of carbapenemase activity in Bacteroides fragilis in positive blood culture, using matrix-assisted laser desorption ionization-time of flight mass spectrometry
Instant screening and verification of carbapenemase activity in Bacteroides fragilis in positive blood culture, using matrix-assisted laser desorption ionization-time of flight mass spectrometry
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DOI：
10.1099/jmm.0.075465-0
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发表时间：
2014-08-01
影响因子：
3
通讯作者：
Soki, Jozsef
中科院分区：
文献类型：
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作者：
Johansson, Asa;Nagy, Elisabeth;Soki, Jozsef
快速鉴定阳性血培养中的分离株对于确保败血症患者的正确治疗非常重要。随着抗菌药物耐药性的增加，快速检测耐药性至关重要。脆弱拟杆菌中与 cfiA 编码的 B 类金属-β-内酰胺酶相关的碳青霉烯类耐药性正在出现。在我们的研究中，我们在血液培养瓶中加入了 26 种具有不同 cfiA 状态和厄他培南 MIC 的脆弱拟杆菌菌株。通过使用 cfiA 阳性和 cfiA 阴性脆弱拟杆菌菌株特异的主光谱，可以筛选分离株的耐药性。为了验证筛选中呈阳性的菌株，进行了碳青霉烯酶测定，其中使用基质辅助激光解吸电离飞行时间质谱 (MALDI-TOF MS) 分析了完整厄他培南和水解厄他培南的特定峰。我们在此表明，可以正确识别脆弱拟杆菌并直接从阳性血培养物沉淀中筛选酶促碳青霉烯类耐药性。尽管存在血液成分，但通过直接鉴定，成功地对沉淀进行了碳青霉烯酶测定，以验证酶的存在。该程序的结果在 3 小时内获得。此外，布鲁克质谱 β-内酰胺酶测定（MSBL 测定）原型软件被证明不仅基于与手动检查光谱相关的算法，而且还通过显示数据集的变化来改进解释。
Rapid identification of isolates in positive blood cultures are of great importance to secure correct treatment of septicaemic patients. As antimicrobial resistance is increasing, rapid detection of resistance is crucial. Carbapenem resistance in Bacteroides fragilis associated with cfiA-encoded class B metallo-beta-lactamase is emerging. In our study we spiked blood culture bottles with 26 B. fragilis strains with various cfiA-status and ertapenem MICs. By using main spectra specific for cfiA-positive and cfiA-negative B. fragilis strains, isolates could be screened for resistance. To verify strains that were positive in the screening, a carbapenemase assay was performed where the specific peaks of intact and hydrolysed ertapenem were analysed with matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). We show here that it is possible to correctly identify B. fragilis and to screen for enzymic carbapenem resistance directly from the pellet of positive blood cultures. The carbapenemase assay to verify the presence of the enzyme was successfully performed on the pellet from the direct identification despite the presence of blood components. The result of the procedure was achieved in 3 h. Also the Bruker mass spectrometric beta-lactamase assay (MSBL assay) prototype software was proven not only to be based on an algorithm that correlated with the manual inspection of the spectra, but also to improve the interpretation by showing the variation in the dataset.