E-Test or Agar Dilution for Metronidazole Susceptibility Testing of Helicobacter pylori: Importance of the Prevalence of Metronidazole Resistance

Jinnan Chen,Hong Lu,Xiao Liang,Yu Huang,Zhaohui Ding

doi:10.3389/fmicb.2022.801537

Jinnan Chen, Hong Lu + Show 3 more

Open Access

https://doi.org/10.3389/fmicb.2022.801537

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Abstract

BackgroundA number of studies have shown that E-test overestimated the presence of Helicobacter pylori resistance compared to agar dilution.ObjectiveThe purpose of this study was to explore whether E-test could be an alternative for agar dilution to detect the metronidazole susceptibility of H. pylori.MethodE-test and agar dilution were used to assess the susceptibility of H. pylori to metronidazole, clarithromycin, and levofloxacin in 281 clinical isolates obtained from China where the resistance was high. Cohen’s kappa analysis, McNemar’s test, and essential and categorical agreement analysis were performed for these two methods.ResultsOverall, the result of the E-test showed a similar prevalence of resistance rate to all antibiotics compared with agar dilution. The essential agreement of the E-test method and agar dilution in the evaluation susceptibility of H. pylori to clarithromycin and levofloxacin was moderate at 89.0 and 79.7%, respectively, but only 45.9% for metronidazole. The results shown by a categorical agreement (CA) between the E-test and agar dilution were 100% for both clarithromycin and levofloxacin. As for metronidazole, the CA was 98.7%, no major error was identified, and the rate of a very major error was 1.8%.ConclusionE-test can be an alternative method to detect the metronidazole susceptibility of H. pylori.

Highlights

All successful infectious disease therapies are directly or indirectly based on susceptibility
The kappa values indicated a substantial agreement for metronidazole (0.96; 95% CI: 0.92–1.00), clarithromycin (1.00; 95% CI: 1.00–1.00), and levofloxacin (1.00; 95% CI: 1.00–1.00) between the E-test and the agar dilution method
The results showed that the minimum inhibitory concentration (MIC) of two strains was 8 ug/ml and the remaining strains were less than 2 ug/ml when interpreted by the agar dilution method

Summary

Introduction

All successful infectious disease therapies are directly or indirectly based on susceptibility. For regions where resistance is common, susceptibility-guided tailored treatment is typically required to achieve high cure rates. This is especially true with Helicobacter pylori infections (Rimbara et al, 2011; Sugano et al, 2015). The worldwide increase in antibiotic-resistant H. pylori has resulted in relatively poor cure rates with empiric therapy (Graham and El-Serag, 2021). Susceptibility Testing of Helicobacter pylori even in regions with only modest levels of resistance, antibiotic susceptibility testing prior to H. pylori treatment has been shown to increase the eradication rate compared to empirical treatment (Wenzhen et al, 2010; Lopez-Gongora et al, 2015). Metronidazole, clarithromycin, and levofloxacin are among the most commonly used antibiotics in the clinical treatment of H. pylori, and the need to assess bacterial antibiotic susceptibility patterns before treatment has received increasing attention (Dang and Graham, 2017). A number of studies have shown that E-test overestimated the presence of Helicobacter pylori resistance compared to agar dilution

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