Antimicrobial resistance rate of Helicobacter pylori isolates and detection of mechanism of clarithromycin resistance / 대한내과학회지

ABSTRACT

BACKGROUND: Antimicrobial resistance is considered as the primary reason for eradication failure of Helicobacter pylori. Resistance to clarithromycin is mostly due to the point mutation in H. pylori 23S rRNA gene. The aims of this study were to determine the primary resistance rate to clarithromycin and metronidazole and to examine the mechanism of clarithromycin resistance in H. pylori isolates. METHODS: Seventy-nine strains were isolated from 73 patients within about five years. The susceptibility of H. pylori isolates to clarithromycin and metronidazole were tested by E-test and broth dilution test. To detect point mutations in the 23S rRNA gene, PCR-RFLP (restriction fragment length polymorphism) was performed. Mutations in clarithromycin-resistant strains also were analyzed by direct sequencing. RESULTS: The resistance rate to clarithromycin (>1 mg/L) and metronidazole (>8 mg/L) were 5.1% and 54.4%, respectively. Annual metronidazole-resistant rates were 43.7% (7/16) in 1996-1997, 61.1% (11/18) in 1998, 55.6% (5/9) in 1999, and 55.6% (20/36) in 2000. Annual clarithromycin- resistant rates were 6.3% (1/16) in 1996-1997, 0% (0/18) in 1998, 11.1% (1/9) in 1999, and 5.6% (2/36) in 2000. Two of 4 clarithromycin-resistant isolates contained the A2144G mutation. One isolate contained A2143G mutation. One isolate possibly contained T2183C mutation. Different strains, isolated separately from antrum and body in 6 patients, showed same susceptibility to clarithromycin. However, different strains in two patients showed different susceptibility to metronidazole. CONCLUSION: No significant increase of resistantce rate to both clarithromycin and metronidazole were found within recent five years. Resistance of H. pylori to clarithromycin was caused by A2144G and A2143G mutation mainly and by T2183C mutation possibly.