Effect of clarithromycin and omeprazole therapy on the diversity and stability of genotypes of Helicobacter pylori from duodenal ulcer patients

The genotypes of multiple isolates of Helicobacter pylori from 17 duodenal ulcer patients in the United Kingdom were compared to determine reasons for treatment failure, Isolates were from antrum and corpus biopsies taken bef ore and after dual therapy with clarithromycin and omeprazole, All isolates were tested for antibiotic resistance and characterised by a novel scheme combining polymerase chain reaction-restriction fragment length polymorphis m (PCR-RFLP) analysis of the ureA + ureB and 23S rRNA genes, vacA signal an d midregion genotypes, and PCR detection of cagA, Combined genotypes of pai red pre- and post-treatment isolates from 8 patients showed an infection wi th a single strain of H. pylori that had acquired resistance to clarithromy cin. In 4 other patients, acquisition of clarithromycin resistance was asso ciated with the presence of different strain types of H, pylori, The remain ing 5 patients had clarithromycin-sensitive isolates. Overall, H, pylori fr om different patients had diverse genotypes, yet most (70%) were colonized by the same predominant and stable strain in both the antrum and corpus, Th ere was no link between the emergence of in vitro clarithromycin resistance and a particular strain genotype for these UK isolates. It was concluded t hat colonization with a clarithromycin-resistant H, pylori was due to selec tion of a resistant strain or clonal variant within the infecting populatio n, Present genomic markers had low predictive value for emergence of resist ance.