Operative Unit of Clinical Microbiology, IRCCS S. Orsola-Malpighi University Hospital, Bologna, Italy.
Operative Unit of Clinical Microbiology, IRCCS S. Orsola-Malpighi University Hospital, Bologna, Italy; Microbiology, DIMES, University of Bologna, Bologna, Italy.
J Glob Antimicrob Resist. 2021 Mar;24:270-274. doi: 10.1016/j.jgar.2020.12.015. Epub 2021 Jan 2.
Current evidence suggests that early diagnosis of sepsis and timely detection of antimicrobial resistance are crucial to improve mortality rates among patients. The aim of this study was to evaluate a rapid method for the identification of Gram-negative bacteria from positive blood cultures (BCs), combined with the detection of extended spectrum β-lactamases (ESβL) and carbapenemases production, by means of MALDI-TOF/MS analysis.
During the study, all BCs positive for Gram-negative rods were selected. Starting from bacterial pellets obtained directly from BC broths, species identification and hydrolysis assays were achieved through MALDI-TOF/MS (Bruker). In particular, we performed a hydrolysis assays of cefotaxime (CTX) and ertapenem (ERT) for the rapid detection of resistance via ESβL and carbapenemases, respectively. These results were compared with the routine workflow, including BC subcultures and confirmation phenotypic methods. Finally, a comparison of the turnaround-time (TAT) between the two protocols was conducted.
Overall, 185 BCs positive for Enterobacteriaceae were collected. In terms of species identification, we observed a concordance of 95.9% comparing MALDI-TOF/MS results to the subculture-based method. The sensitivity and specificity for CTX hydrolysis assay were 91.1% and 92%, respectively; ERT hydrolysis assay showed a sensitivity of 96.2% and a specificity of 99.2%. The TAT of the proposed MALDI TOF/MS-based protocol was significantly lower compared with the routine workflow (P < 0.0001).
The proposed protocol can provide reliable bacterial identification and data concerning β-lactam resistance in only 3 hours, positively improving management of patients in terms of antimicrobial stewardship.
目前的证据表明，早期诊断脓毒症和及时发现抗菌药物耐药性对于提高患者的死亡率至关重要。本研究旨在评估一种从阳性血培养（BC）中快速鉴定革兰氏阴性菌的方法，结合 MALDI-TOF/MS 分析检测扩展谱β-内酰胺酶（ESβL）和碳青霉烯酶的产生。
在研究过程中，选择所有革兰氏阴性杆菌阳性的 BC。从 BC 肉汤中直接获得细菌沉淀开始，通过 MALDI-TOF/MS（布鲁克）进行种属鉴定和水解试验。特别是，我们对头孢噻肟（CTX）和厄他培南（ERT）进行水解试验，分别快速检测 ESβL 和碳青霉烯酶的耐药性。将这些结果与包括 BC 传代和确认表型方法在内的常规工作流程进行比较。最后，对两种方案的周转时间（TAT）进行了比较。
总体而言，共收集了 185 株肠杆菌科阳性的 BC。在种属鉴定方面，我们观察到 MALDI-TOF/MS 结果与基于传代的方法的一致性为 95.9%。CTX 水解试验的敏感性和特异性分别为 91.1%和 92%；ERT 水解试验的敏感性为 96.2%，特异性为 99.2%。与常规工作流程相比，所提出的 MALDI TOF/MS 基于方案的 TAT 显著降低（P<0.0001）。
该方案仅需 3 小时即可提供可靠的细菌鉴定和有关β-内酰胺类耐药的数据，在抗菌药物管理方面积极改善患者的管理。
