Department of Bio-Medical Laboratory Science and Management, Vidyasagar University, Midnapore, West Bengal, India.
Department of Microbiology, Tata Medical Center, Kolkata, West Bengal, India.
Indian J Med Microbiol. 2020 Jan-Mar;38(1):58-65. doi: 10.4103/ijmm.IJMM_19_480.
Unavailability of optimal susceptibility testing (ST) challenges the clinical use of colistin. Broth microdilution (BMD), which is the reference for colistin ST, is inconvenient for diagnostics. Vitek2 and E-test although technically easier, are no longer recommended.
For the evaluation of Vitek2 and E-test in reference with BMD, a total of 138 Gram-negative bacilli (GNB) especially carbapenem-resistant isolates from Tata Medical Center, Kolkata, India, were included during 2017-2018. The evaluation was performed only for Enterobacteriaceae (n = 102), but not for non-fermentative GNB (n = 36) due to lack of colistin-resistant (COL) isolates.
Of 138 isolates, meropenem, colistin and dual resistance were detected in 110 (79.7%), 31 (22.5%) and 21 (15.2%) of isolates, respectively. Using the European Committee on Antimicrobial Susceptibility Testing guidelines (susceptible, ≤2 μg/ml), Vitek2 performed better than E-test (essential agreement, 92.2% vs. 63.7%; categorical agreement, 94.1% vs. 93.1%; very major error [VME], 10% vs. 23.3%). However, Vitek2 overcalled resistance than E-test (major error, 4.2% vs. 0%). Considering Chew et al. proposed breakpoints (susceptible, ≤1 μg/ml), VMEs declined for both test (6.7% vs. 10%), but still remained unacceptable. Of eight colistin-heteroresistant isolates, two VME were categorised by Vitek2, one VME was by E-test, and two were uninterpretable. Both Vitek2 and E-test are unreliable. Further studies correlating minimum inhibitory concentrations with clinical outcome are needed to determine the accurate breakpoints for better patient management.
由于缺乏最佳药敏检测（ST），使得粘菌素的临床应用受到挑战。肉汤微量稀释法（BMD）是粘菌素 ST 的参考方法，但不方便用于诊断。Vitek2 和 E 试验虽然在技术上更简单，但已不再推荐使用。
为了评估 Vitek2 和 E 试验与 BMD 的相关性，共纳入了 2017 年至 2018 年期间来自印度加尔各答塔塔医疗中心的 138 株革兰氏阴性菌（GNB），特别是耐碳青霉烯类的分离株。仅对肠杆菌科（n = 102）进行了评估，而未对非发酵 GNB（n = 36）进行评估，因为缺乏粘菌素耐药（COL）分离株。
在 138 株分离株中，分别有 110 株（79.7%）、31 株（22.5%）和 21 株（15.2%）检测到美罗培南、粘菌素和双重耐药。根据欧洲抗菌药物敏感性试验委员会（EUCAST）指南（敏感，≤2 μg/ml），Vitek2 的表现优于 E 试验（符合率，92.2%比 63.7%；分类符合率，94.1%比 93.1%；重大错误[VME]，10%比 23.3%）。然而，Vitek2 比 E 试验更容易出现耐药性误判（主要错误，4.2%比 0%）。考虑到 Chew 等人提出的折点（敏感，≤1 μg/ml），两种试验的 VME 均有所下降（6.7%比 10%），但仍不可接受。在 8 株粘菌素异质性耐药分离株中，Vitek2 分类出 2 株 VME，E 试验分类出 1 株 VME，2 株结果不可解释。Vitek2 和 E 试验均不可靠。需要进一步研究最小抑菌浓度与临床结果的相关性，以确定准确的折点，从而更好地管理患者。
