2072. Multicenter Evaluation of the Etest Versus Agar Dilution for Susceptibility Testing of Helicobacter pylori
Session: Poster Abstract Session: Diagnostics: Resistance Testing
Saturday, October 6, 2018
Room: S Poster Hall
  • ID week 2018 poster_SS-2.pdf (552.5 kB)
  • Background: Helicobacter pylori is associated with peptic ulcer disease and gastric malignancy. Antimicrobial susceptibility testing (AST) is often requested for patients who fail eradication therapy. The 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 (bioMerieux) as a method for H. pylori AST in comparison to AD

    Methods: Frozen stocks of 82 H. pylori isolates with AD results previously reported by Mayo Clinic were prepared from the same plate for distribution to participating laboratories. Etest was performed at ARUP Laboratories and Cleveland Clinic (CC). For Etest, isolates were incubated for 72 h in a microaerobic atmosphere. Aged Mueller-Hinton agar with 5% sheep blood plates were inoculated with a 3 McFarland suspension prepared in brain heart infusion broth. Etest strips were applied and MICs read after 72 h of microaerobic incubation. Results were interpreted by applying CLSI and EUCAST breakpoints. Categorical agreement (CA), very major, major and minor errors (VME, ME, and mE) were determined for Etest using AD as the reference method. Isolates with errors were repeat tested in duplicate by Etest to determine the final results summarized below.

    Results: For clarithromycin, 65% of isolates were resistant (R) by AD; Etest results at each laboratory showed 97.5% CA (1 mE and 1 ME). For tetracycline, only 2.5% of isolates were R by AD; a single VME occurred at both ARUP and CC (98.8% CA) with the same isolate. The AD dilutions tested for amoxicillin prevented interpretation with EUCAST breakpoints. With one exception, amoxicillin Etest results were susceptible (S, ≤0.125 mg/L) at both laboratories (98.8% of MICs ± one dilution). Applying levofloxacin EUCAST breakpoints (S, ≤1 mg/L) to interpret ciprofloxacin results, 57.8% of isolates were R by AD. ARUP CA was 97.5% (1 ME, 1 VME) and CC CA was 96.3% (1 ME, 2 VMEs).

    Conclusion: Clarithromycin, tetracycline, and ciprofloxacin Etest results for H. pylori showed acceptable CA (>95%) at both testing sites compared to the AD reference method. The comparative ease of performance and reproducibility of the Etest may help standardize it as an AST method for H. pylori.

    Salika M. Shakir, Ph.D., D(ABMM)1,2, Joshua Otiso, MPH, MLS (ASCP)3, George Keller, SM (ASCP)3, Hillary Van Heule, MT (ASCP)3, Peggy Kohner, MT(ASCP)4, Nicolynn Cole, MT(ASCP)4, Audrey N. Schuetz, MD4, Sandra S. Richter, MD3 and Marc Roger Couturier, Ph.D., D(ABMM)1,2, (1)ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT, (2)Department of Pathology, University of Utah, Salt Lake City, UT, (3)Department of Laboratory Medicine, Cleveland Clinic, Cleveland, OH, (4)Division of Clinical Microbiology, Mayo Clinic, Rochester, MN


    S. M. Shakir, None

    J. Otiso, None

    G. Keller, None

    H. Van Heule, None

    P. Kohner, None

    N. Cole, None

    A. N. Schuetz, None

    S. S. Richter, bioMerieux: Grant Investigator , Research grant . BD Diagnostics: Grant Investigator , Research grant . Roche: Grant Investigator , Research grant . Hologic: Grant Investigator , Research grant . Diasorin: Grant Investigator , Research grant . Accelerate: Grant Investigator , Research grant . Biofire: Grant Investigator , Research grant .

    M. R. Couturier, None

    Findings in the abstracts are embargoed until 12:01 a.m. PDT, Wednesday Oct. 3rd with the exception of research findings presented at the IDWeek press conferences.