FIG. 3.
Comparison of the average of all paired agar dilution (AD) and E test (ET) MICs of clarithromycin (A) and metronidazole (B) for each of the 13 H. pylori strains. Ra, the NCCLS cutoff for clarithromycin resistance is an MIC equal to or greater than 1 μg/ml; Rb, the generally accepted cutoff for metronidazole resistance is an MIC greater than 8 μg/ml. For clarithromycin the overall correlation between the agar dilution method and E test was slightly higher than that for metronidazole, but by both methods with clarithromycin and metronidazole, there was a clear distinction between sensitive and resistant strains.