Chromatograms of PCR-RFLP assays and sequencing for detection of nucleotide alterations of 23S rRNA. H. Pylori 26695 and CLRr-1 were used as negative and positive control of A2143G mutation. BsaI digestion of the PCR products of representative samples was displayed on 8% PAGE gel. The 289 bp A2143G-positive PCR products were cleaved into a 199 bp and a 90 bp fragments (A). The A2143G mutation was also confirmed by sequencing of the PCR products of 23S rRNA (B, displayed 2140–2154 fragment). H. Pylori 26695 and a 2142G clone were used as negative and positive control of A2142G mutation. MboII digestion of the PCR products of representative samples was displayed on 2% agarose gel. The 289 bp A2142G-positive PCR products of 2142G were cleaved into an 182 bp and a 107 bp fragments. The PCR product of GJ2040 was cleaved into a 164 bp and a 125 bp fragments; and the product of GJ2111 was cleaved into 245 bp and 44 bp fragment(s) (C). The A2142G and other mutations were confirmed by sequencing (D). Two new MboII-sensitive sequences were characterized as CTTCA (2222–2226) for GJ2040 and GAAG (2081–2084) for GJ2111.