Evolution of resistance to metronidazole and clarithromycin in Helicobacter pylori clinical isolates from Spain.

The aim of this study was to determine the frequency of resistance to amoxycillin, tetracycline, metronidazole and clarithromycin in 282 Helicobacter pylori clinical isolates from Spain and to evaluate the evolution of resistance over the five years of this study. The overall percentage of resistance was 19.9% for metronidazole and 3.5% for clarithromycin. Resistance to metronidazole rose from 9% in 1991 to 21.6% in 1995, although 33.3% resistance was found in 1993. Clarithromycin resistance was not detected in 1991 or 1992 and the rate was 4%, 3.4% and 4.4% in 1993, 1994 and 1995, respectively. No amoxycillin or tetracycline resistance was found.