梯度条试验致脆弱拟杆菌对阿莫西林/克拉维酸药敏结果错误。

False amoxicillin/clavulanic acid susceptibility in Bacteroides fragilis using gradient strip tests.

机构信息

Department of Medical Microbiology, University Medical Center Utrecht, Internal mail no G.04.614, P.O. Box 85500, 3508 GA, Utrecht, The Netherlands.

出版信息

Anaerobe. 2021 Jun;69:102358. doi: 10.1016/j.anaerobe.2021.102358. Epub 2021 Mar 17.

DOI:10.1016/j.anaerobe.2021.102358

PMID:33741507

Abstract

BACKGROUND

Repeatedly, too low MIC results were obtained in Bacteroides fragilis quality assessment strains, using gradient strip tests with a ratio of amoxicillin:clavulanic acid of 2:1. We aimed to find the most accurate available gradient strip tests for susceptibility testing of amoxicillin/clavulanic acid in B. fragilis in comparison with agar dilution with EUCAST methodology and breakpoints.

METHODS

Twenty-seven clinical B. fragilis isolates were investigated using gold standard EUCAST amoxicillin/clavulanic acid agar dilution (fixed clavulanic acid concentration at 2 mg/L, with increasing amoxicillin concentrations) as well as three commercial gradient strip tests: XL (ratio), AUG (ratio) or AMC (fixed concentration).

RESULTS

Using agar dilution (fixed concentration), 19 isolates were susceptible, 1 isolate was susceptible increased exposure (I) and 7 isolates were resistant. Categorical agreement of the gradient strip tests with agar dilution (fixed concentration) was 70% for XL (ratio), 71% for AUG (ratio) and 89% for AMC (fixed concentration). Very major error rates in comparison with agar dilution (fixed concentration) were 100%, 0%, and 0%, respectively.

CONCLUSIONS

EUCAST breakpoint usage in amoxicillin/clavulanic acid susceptibility tests for B. fragilis should be accompanied by EUCAST methodology. When using alternative methods such as gradient strip tests, a higher degree of alignment with EUCAST methodology, such as using fixed clavulanic acid concentrations, improves precision.

摘要

背景

在使用阿莫西林：克拉维酸比例为 2:1 的梯度条测试对脆弱拟杆菌质量评估菌株进行检测时，反复得到过低的 MIC 结果。我们旨在找到最准确的可用梯度条测试，用于比较欧盟药敏试验委员会（EUCAST）方法和折点的脆弱拟杆菌中阿莫西林/克拉维酸的药敏试验。

方法

使用金标准 EUCAST 阿莫西林/克拉维酸琼脂稀释法（固定克拉维酸浓度为 2mg/L，增加阿莫西林浓度）以及三种商业梯度条测试：XL（比例）、AUG（比例）或 AMC（固定浓度），对 27 株临床分离的脆弱拟杆菌进行了研究。

结果

使用琼脂稀释法（固定浓度），19 株为敏感，1 株为敏感增加暴露（I），7 株为耐药。与琼脂稀释法（固定浓度）相比，梯度条测试 XL（比例）、AUG（比例）和 AMC（固定浓度）的分类一致性分别为 70%、71%和 89%。与琼脂稀释法（固定浓度）相比，非常大的错误率分别为 100%、0%和 0%。