摘要AIM: To characterize the types of mutations present in the 23S rRNA genes of Malaysian isolates of clarithromycin-resistant Helicobacter pylori (H pylori).METHODS: Clarithromycin susceptibility of H pylori isolates was determined by E test. Analyses for point mutations in the domain V of 23S rRNA genes in clarithromycin-resistant and -sensitive strains were performed by sequence analysis of amplified polymerase chain reaction products. Restriction fragment length polymorphism was performed using BsaⅠ and Mbo Ⅱ enzymes to detect restriction sites that correspond to the mutations in the clarithromycin-resistant strains.RESULTS: Of 187 isolates from 120 patients, four were resistant to clarithromycin, while 183 were sensitive. The MIC of the resistant strains ranged from 1.5 to 24 μg/mL. Two isolates had an A2142G mutation and another two had A2143G mutations. A T2182C mutation was detected in two out of four clarithromycin-resistant isolates and in 13 of 14 clarithromycin-sensitive isolates. Restriction enzyme analyses with Bsa I and Mbo n were able to detect the mutations.CONCLUSION: Clarithromycin resistance is an un-common occurrence among Malaysian isolates of Hpylori strains and the mutations A2142G and A2143G detected were associated with low-level resistance.