Comparison of the E Test and Agar Dilution Method for Antimicrobial Suceptibility Testing of Helicobacter pylori

Abstract

A multicentre study was carried out in order to validate the E test in comparison with the reference agar dilution method for testing the susceptibility of Helicobacter pylori to amoxicillin, clarithromycin, and metronidazole. Ten clinical isolates and one control collection isolate (Helicobacter pylori ATCC 43504) were tes ted blindly at four centres according to a uniform methodology. The E test showed excellent intra- and inter-laboratory correlations with the agar dilution method for amoxicillin and clarithromycin (>98% agreement within 2 log₂ dilution steps). For metronidazole, however, the E test revealed significantly higher minimum inhibitory concentration values (>2 log₂) against 5 of the 10 Helicobacter pylori strains tested. Overall, neither method was found reliable for testing the susceptibility of Helicobacter pylori to metronidazole, since both tended to lack reproducibility.