Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah, USA.
ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, Utah, USA.
Microbiol Spectr. 2022 Apr 27;10(2):e0211121. doi: 10.1128/spectrum.02111-21. Epub 2022 Mar 7.
Helicobacter pylori is an important human pathogen associated with peptic ulcer disease, dyspepsia, and gastric malignancy. Antimicrobial susceptibility testing (AST) is often requested for patients who fail eradication therapy. The Clinical and Laboratory Standards Institute (CLSI) reference method, agar dilution (AD), is not performed in most laboratories and maintaining organism viability during transit to a reference laboratory is difficult. We assessed the performance of the Etest (bioMérieux) as a method for H. pylori AST in comparison to AD. Etest MICs were determined for 83 H. pylori isolates at ARUP and Cleveland Clinic (CC). Categorical agreement (CA), very major, major, and minor errors (VME, ME, and mE) were determined for Etest using AD performed at Mayo Clinic Laboratories as the reference method. Testing on isolates with errors was repeated to determine final results summarized below. For clarithromycin, 66.3% of isolates were resistant (R) by AD; Etest results at each laboratory showed 1mE (1.2%) and 1 ME (3.8%). For tetracycline, only 2 isolates were R by AD; a single VME occurred at both sites (98.8% CA, 50% VME) with the same isolate. Applying EUCAST levofloxacin breakpoints to interpret ciprofloxacin results, 60.2% of isolates were R by AD; ARUP CA was 97.6% (1 ME (3%), 1 VME (2%)) and CC CA was 96.3% (1 ME (3%), 2 VMEs (4%)). Despite high error rates, the categorical agreement was acceptable (>90%) for all three antibiotics between AD and Etest. In-house susceptibility testing by gradient diffusion can allow for testing of fastidious organisms that may not survive transport to specialized laboratories; however, the method is not without technical challenges. Characterization of resistance mechanisms, increased AD dilutions, and testing from the same inoculum may determine if the observed errors reflect technical issues or breakpoints that need optimization. Routine antimicrobial susceptibility testing (AST) of Helicobacter pylori by agar dilution is difficult to perform and not practical in most clinical microbiology laboratories. The Etest gradient diffusion method can be a reliable alternative for H. pylori AST with the advantage of being a less laborious quantitative method. This work reveals that an optimized Etest method can provide acceptable performance for H. pylori AST and describes the challenges associated with this methodology.
幽门螺杆菌是一种与消化性溃疡病、消化不良和胃癌相关的重要人类病原体。对于未能根除治疗的患者，通常需要进行抗菌药物敏感性测试（AST）。临床和实验室标准研究所（CLSI）的参考方法，琼脂稀释法（AD），在大多数实验室中无法进行，而且在将生物体运送到参考实验室的过程中保持其活力是困难的。我们评估了 Etest（生物梅里埃）作为幽门螺杆菌 AST 方法的性能，与 AD 进行了比较。在 ARUP 和克利夫兰诊所（CC）对 83 株幽门螺杆菌分离株进行了 Etest MIC 测定。使用梅奥诊所实验室进行的 AD 作为参考方法，确定了 Etest 的分类一致性（CA）、非常大、大、小误差（VME、ME 和 mE）。对有误差的分离物进行重复测试，以确定以下总结的最终结果。对于克拉霉素，66.3%的分离物通过 AD 表现为耐药（R）；每个实验室的 Etest 结果显示 1mE（1.2%）和 1 ME（3.8%）。对于四环素，只有 2 株分离物通过 AD 表现为 R；在两个地点都发生了单个 VME（98.8%的 CA，50%的 VME），同一分离物。应用 EUCAST 左氧氟沙星断点来解释环丙沙星结果，60.2%的分离物通过 AD 表现为 R；ARUP 的 CA 为 97.6%（1 ME（3%），1 VME（2%）），CC 的 CA 为 96.3%（1 ME（3%），2 VMEs（4%））。尽管误差率较高，但 AD 和 Etest 之间对于所有三种抗生素的分类一致性都在可接受范围（>90%）。通过梯度扩散进行的内部敏感性测试可以允许对可能无法在专门实验室中存活的挑剔生物体进行测试；然而，该方法并非没有技术挑战。耐药机制的特征描述、增加 AD 稀释度以及从相同接种物进行测试，可能会确定观察到的误差是否反映了技术问题或需要优化的断点。通过琼脂稀释法对幽门螺杆菌进行常规抗菌药物敏感性测试（AST）很难进行，并且在大多数临床微生物学实验室中并不实用。Etest 梯度扩散法可以作为一种可靠的替代方法，用于幽门螺杆菌 AST，其优势在于它是一种不那么费力的定量方法。这项工作表明，优化的 Etest 方法可以为幽门螺杆菌 AST 提供可接受的性能，并描述了与该方法相关的挑战。
