Molecular diagnosis of Helicobacter pylori by PCR and RLFP detection of the domain V of the 23S rRNA mutations A2142G and A2143G responsible for clarithromycin resistance. A. Representation of the H. pylori 23S coding gene (Genbank:HPU27270), position of the primers used for PCR and of the A2142 and A2143 from fraction V of the 23S rDNA, size of the fragments obtained with restriction enzymes BsaI and MboII in PCR fragments containing the mutations A2142G and A2143G, and internal BsaI restriction site of the 768 bp amplicon, are indicated. B, C and D. Agarose gel stained with ethidium bromide containing a PCR diagnostic analysis, restriction analysis of the 768pb amplicon with MboII and BsaI, respectively. 1–10 correspond to different human biopsy specimens; C-, negative control of PCR, M-100 bp ladder purchased from Invitrogen. Sizes of the DNA fragments are indicated on the left or right of each gel figure.