Resistance of helicobacter pylori to metronidazole, tetracycline and amoxycillin.

Resistance to metronidazole, tetracycline and amoxycillin, and beta-lactamase production were determined for 153 clinical isolates of Helicobacter pylori. Of these isolates, 77.8% were resistant to metronidazole (MIC > 8 mg/L), 58.8% to tetracycline (MIC > 16 mg/L) and 71.9% to amoxycillin (MIC > 0.5 mg/L); 39.2% were multiresistant. Resistance to metronidazole was more common in isolates from females than in those from males (P < 0.05). None of the isolates produced beta-lactamase, so the mechanism of amoxycillin resistance was not linked to production of beta-lactamase.