Accelerate Diagnostics, Tucson, Arizona, USA
University of Arizona, Department of Pathology, Tucson, Arizona, USA.
J Clin Microbiol. 2019 Feb 27;57(3). doi: 10.1128/JCM.01797-18. Print 2019 Mar.
In 2019, the Clinical and Laboratory Standards Institute (CLSI) published revisions to the ciprofloxacin and levofloxacin breakpoints. We evaluated the performance of disk diffusion and Etest compared to that of reference broth microdilution by use of the revised breakpoints. Fifty-eight isolates with ciprofloxacin MICs of 0.5 μg/ml or 1.0 μg/ml on initial testing were specifically selected for evaluation. These MICs are susceptible by the 2018 breakpoints and not susceptible by the 2019 breakpoints. For ciprofloxacin disk diffusion, the categorical agreement (CA) was 46.6%, with 0 very major errors (VME), 4 major errors (ME) (21.1%), and 27 minor errors (mE) (46.6%) using the 2019 CLSI disk breakpoints. For levofloxacin, the CA was 72.4%, with 0 VME, 0 ME, and 16 mE (27.6%) using the 2019 CLSI disk breakpoints. Using an error rate-bound evaluation method, levofloxacin but not ciprofloxacin disk diffusion yielded an acceptable minor error rate of <40% for isolates with an MIC plus or minus 1 doubling dilution of the intermediate breakpoint. For Etest compared to the reference broth microdilution, the essential agreement was 100% for both ciprofloxacin and levofloxacin and the CA was 81.0% and 65.5%, respectively. No VME or ME were observed by Etest, and 11 minor errors for ciprofloxacin (19.0%) and 20 (34.5%) for levofloxacin were observed. By the error rate-bound method, the minor error rate for ciprofloxacin was acceptable, but minor error rates for levofloxacin remained outside the acceptance range (i.e., 42.6% for isolates with an MIC within 1 dilution of the breakpoint). In general, the disk diffusion and Etest methods performed well with this challenging collection of isolates, although laboratories must be aware of minor errors, particularly for isolates with results near the breakpoint.
2019 年，临床和实验室标准协会（CLSI）发布了对环丙沙星和左氧氟沙星折点的修订版。我们使用修订后的折点评估了纸片扩散法和 Etest 与参考肉汤微量稀释法的性能。特别选择了初始检测中环丙沙星 MIC 为 0.5μg/ml 或 1.0μg/ml 的 58 株分离株进行评估。这些 MIC 在 2018 年的折点下是敏感的，而在 2019 年的折点下是不敏感的。对于环丙沙星纸片扩散法，使用 2019 年 CLSI 纸片折点时，分类一致性（CA）为 46.6%，0 个非常大错误（VME），4 个主要错误（ME）（21.1%）和 27 个次要错误（mE）（46.6%）。对于左氧氟沙星，使用 2019 年 CLSI 纸片折点时，CA 为 72.4%，0 个 VME、0 个 ME 和 16 个 mE（27.6%）。使用误差率边界评估方法，对于 MIC 加或减 1 倍稀释的中介折点的分离株，左氧氟沙星但不是环丙沙星纸片扩散法产生可接受的<40%的次要错误率。与参考肉汤微量稀释法相比，Etest 对于环丙沙星和左氧氟沙星的基本一致性均为 100%，CA 分别为 81.0%和 65.5%。Etest 未观察到 VME 或 ME，观察到环丙沙星的 11 个次要错误（19.0%）和左氧氟沙星的 20 个次要错误（34.5%）。通过误差率边界方法，环丙沙星的次要错误率是可以接受的，但左氧氟沙星的次要错误率仍在可接受范围之外（即在距离折点 1 倍稀释范围内的分离株中为 42.6%）。总的来说，尽管实验室必须注意到次要错误，特别是对于接近折点的分离株，但纸片扩散法和 Etest 方法在这个具有挑战性的分离株集合中表现良好。
