Microbiology and Virology Unit, University Hospital Città della Salute e della Scienza di Torino, Turin, Italy.
Department of Public Health and Paediatrics, University of Torino, Turin, Italy.
J Antimicrob Chemother. 2022 Sep 30;77(10):2632-2641. doi: 10.1093/jac/dkac230.
To evaluate a rapid diagnostic algorithm based on MALDI-TOF MS, lateral flow immunoassays (LFIAs) and molecular testing performed directly from positive blood cultures (BCs) for Gram-negative species identification and detection of CTX-M extended-spectrum β-lactamases and main carbapenemases.
Non-duplicate BCs positive to Gram-negative bacteria at microscope examination were subjected to species identification by direct MALDI-TOF MS following recovery of bacterial pellet by Rapid MBT Sepsityper® kit. Subsequently, NG-Test® CARBA 5 and NG-Test® CTX-M MULTI LFIAs were performed according to identified microbial species. Eazyplex® SuperBug CRE molecular assay was performed in cases of NG-Test® CARBA 5 negative results in patients with documented carbapenemase-producers carriage. Results of rapid diagnostic workflow were compared with those obtained by conventional diagnostic routine.
Overall, the direct MALDI-TOF MS protocol allowed reliable identification to the species level of 92.1% of the 2133 monomicrobial BCs. Rate of matched identification was significantly higher for Enterobacterales (97.3%) in comparison to non-fermenting Gram-negative species (80.2%), obligate anaerobic bacteria (42.1%) and fastidious Gram-negative species (41.5%). The overall sensitivity of NG-Test® CARBA 5 and NG-Test® CTX-M MULTI was 92.2% and 91.6%, respectively. Integration of Easyplex® SuperBug CRE allowed the detection of blaKPC mutants associated with ceftazidime/avibactam resistance, reaching 100% sensitivity in carbapenemase detection. Both LFIAs and molecular testing showed no false-positive results.
Algorithms based on MALDI-TOF MS, LFIAs and molecular testing may represent a cost-effective tool to timely identify Gram-negative species and detect resistance markers directly from BCs. According to local epidemiology, these results may allow antimicrobial stewardship interventions including prompt use of new approved drugs.
评估一种基于 MALDI-TOF MS、侧向流动免疫分析（LFIAs）和直接从革兰氏阴性菌阳性血培养物（BC）中进行的分子检测的快速诊断算法，用于革兰氏阴性菌的种属鉴定以及检测 CTX-M 超广谱β-内酰胺酶和主要碳青霉烯酶。
对显微镜检查革兰氏阴性菌阳性的非重复 BC 进行直接 MALDI-TOF MS 分析，方法是使用 Rapid MBT Sepsityper®试剂盒回收细菌沉淀后进行。随后，根据鉴定的微生物种类进行 NG-Test®CARBA 5 和 NG-Test®CTX-M MULTI LFIAs 检测。如果 NG-Test®CARBA 5 检测结果为阴性，且患者有明确的碳青霉烯酶产生菌携带史，则进行 Eazyplex®SuperBug CRE 分子检测。将快速诊断工作流程的结果与常规诊断常规的结果进行比较。
总体而言，直接 MALDI-TOF MS 方案可使 2133 株单微生物 BC 中 92.1%的菌株可靠地鉴定到种水平。肠杆菌目（97.3%）的匹配鉴定率明显高于非发酵革兰氏阴性菌（80.2%）、专性厌氧菌（42.1%）和苛养革兰氏阴性菌（41.5%）。NG-Test®CARBA 5 和 NG-Test®CTX-M MULTI 的总体敏感性分别为 92.2%和 91.6%。整合 Eazyplex®SuperBug CRE 可检测与头孢他啶/阿维巴坦耐药相关的 blaKPC 突变体，在检测碳青霉烯酶时达到 100%的敏感性。两种 LFIAs 和分子检测均未出现假阳性结果。
基于 MALDI-TOF MS、LFIAs 和分子检测的算法可能是一种具有成本效益的工具，可直接从 BC 中快速鉴定革兰氏阴性菌并检测耐药标记物。根据当地的流行病学情况，这些结果可能允许进行抗菌药物管理干预，包括及时使用新批准的药物。
