RESUMO
Forty-four strains of Helicobacter pylori were isolated from Kosin Medical Center were tested of resistance to antimicrobial agents, and the mechanism of resistance to clarithromycin was investigated. We determined the MICs of amoxicillin, amoxicillin/clavulanic acid, clarithromycin, and metronidazole by agar and broth dilution method. To detect the mutations of 23S rRNA which is associated with clarithromycin resistance, a 3'-mismatched polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis with restriction enzymes BbsI and BsaI were performed. The nucleotide sequence of 23S rRNA was determined. All H. pylori strains appeared to be susceptible to amoxicillin/clavulinic acid, but 2.3% of strains (1 strain) are resistant to amoxicillin, 13.6% (6 strains) to clarithromycin, and 15.9% (7 strains) to metronidazole. No PCR products was observed by the 3'-mismatched PCR. A 291 bp of PCR product was not digested by BbsI, but was digested by BsaI, which was a characteristic of the A2143G point mutation in the 23S rRNA gene. The nucleotide sequencing analysis revealed that all resistant strains had A2143G, T2182C, and T2244C mutations in 23S rRNA gene.