The resistance rates of the antibiotics used in primary treatment of H. pylori infections in Malaysia are low, and multi-antibiotic-resistant strains are uncommon. Infections with mixed populations of metronidazole-sensitive and -resistant strains were also observed. However, the high metronidazole MIC values seen among the metronidazole-resistant strains are a cause for concern.

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 Bsa Ⅰ and Mbo Ⅱ enzymes to detect restriction sites that correspond to the mutations in the clarithromycinresistant 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 Ⅱ were able to detect the mutations. CONCLUSION:Clarithromycin resistance is an uncommon occurrence among Malaysian isolates of H pylori strains and the mutations A2142G and A2143G detected were associated with low-level resistance.