The resistance of Helicobacter pylori to the recently available antibiotic treatment regimens has been a growing problem. We investigated the prevalence of H. pylori resistance to clarithromycin, metronidazole, and amoxicillin among 51 H. pylori isolates from Japanese children. In addition, the mutations of the corresponding gene were studied by PCR and restriction fragment length polymorphism analysis. Primary resistance to clarithromycin, metronidazole, and amoxicillin was detected in 29, 24, and 0% of strains, respectively. The eradication rates in clarithromycin-susceptible and -resistant strains were 89 and 56%, respectively (P < 0.05). The prevalence of strains with acquired resistance to clarithromycin (78%) was higher than that of strains with primary resistance (P < 0.01). Among the clarithromycin-resistant strains studied, 92% showed cross-resistance to azithromycin. No acquired resistance to amoxicillin was demonstrated. The A2144G mutation in the 23S rRNA gene was detected in 11 of 12 (92%) clarithromycin-resistant strains tested, whereas the mutation was not detected in any of the 15 susceptible strains. The deletion of the rdxA gene was not demonstrated in any of the strains. The results indicate that a high prevalence of clarithromycin-resistant strains is associated with eradication failure. Testing of susceptibility to clarithromycin is recommended.In adults, Helicobacter pylori plays an important role in the pathogenesis of chronic gastritis, peptic ulcer disease, and possibly, gastric carcinoma. H. pylori infection is also associated with chronic gastritis and duodenal ulcer in children (5, 13). Eradication of the organism not only accelarates ulcer healing (14) but also prevents long-term ulcer relapse (12). Recently, proton pump inhibitor (PPI)-based eradication regimens containing two antibiotics have been demonstrated to have high eradication rates (greater than 90%) (3, 22). Amoxicillin, clarithromycin, and metronidazole are the most frequently used antibiotics for the treatment of H. pylori infection. However, antibiotic resistance frequently causes failure of eradication of H. pylori (1,16,21). The resistance of H. pylori to the recently available antibiotic treatment regimens has been a growing problem. In developed countries, metronidazole resistance is found in 10 to 50% of adult patients infected with H. pylori (1, 10, 11), whereas virtually all strains are resistant to the agent in developing countries (26). On the other hand, although the rates of clarithromycin resistance are relatively low, ranging from 2 to 15% (1, 2, 10, 11, 27), the rate of clarithromycin resistance has been increasing during recent years.With regard to antibiotic resistance, however, there have been few reports of antibiotic resistance in children 2, 17, 23; M. Lopez-Brea, M. Martinez, D. Domingo, and T. Alarcon, abstract from the XIII International Workshop on Gastroduodenal Pathology and Helicobacter pylori, Gut 47(Suppl. 1): A95, 2000], and its clinical significance remains to be established. The purpose ...

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We determined the MICs of clarithromycin for 32 Helicobacter pylori strains isolated from gastric mucosa of patients, by using microdilution broth method under different microaerobic conditions (CO2: 5% and 15%). The pH of broth was more acidic at 15% CO2 than that of at 5% CO2. The MICs of clarithromycin for all H. pylori strains at 15% CO2 condition were higher than that of clarithromycin at 5% CO2 condition. Comparing the MICs with the results of eradication therapy, we concluded that the measurement of MIC under 5%CO2 condition is more useful for expecting the clinical outcome.