Drug combinations with amoxycillin reduce selection of clarithromycin resistance during Helicobacter pylori eradication therapy.

This study investigated the relationship between the drug combinations of the eradication regimens and the prevalence of acquired resistance to clarithromycin. Of 540 patients treated with anti-Helicobacter pylori regimens containing clarithromycin, 55 patients (31 males, mean age, 45.6 years) with failed eradication of H. pylori that was susceptible to clarithromycin before treatment were included. The E test was used to test for susceptibility to clarithromycin (minimum inhibitory concentration (MIC) <1 mg/l). Of the 55 patients, 33 (60.0%) developed clarithromycin resistance after failed eradication. Of the dual therapies, the combination of a proton pump inhibitor (PPI) and clarithromycin resulted in 88.9% (8/9) of the patients acquiring clarithromycic-resistance. With the triple therapies, the percentages of patients acquiring clarithromycin resistant strains after using a PPI+clarithromycin+amoxycillin or a PPI+clarithromycin+metronidazole were 38.7% (12/31) and 90.0% (9/10), respectively (P<0.01). These data suggest that regimens containing amoxycillin may prevent the selection of secondary clarithromycin resistance.