ANALYSIS AND TYPING OF THE VACA GENE FROM CAGA-POSITIVE STRAINS OF HELICOBACTER-PYLORI ISOLATED IN JAPAN

Approximately 50% of Helicobacter pylori strains produce a cytotoxin t hat is encoded by vacA and that induces vacuolation of eukaryotic cell s, Mosaicism in vacA alleles was reported, and there are three differe nt families of vacA signal sequences (s1a, s1b, and s2) and two differ ent families of middle-region alleles (m1 and m2),In addition, the vac A genotype of a strain is associated with its cytotoxin phenotype and its capacity to induce peptic ulceration. To clarify the strain divers ity of H. pylori in Japan, 87 Japanese clinical isolates of H. pylori (40 from patients with chronic atrophic gastritis, 25 from patients wi th duodenal ulcer, 16 from patients with gastric ulcer, 3 from patient s with both duodenal and gastric ulcers, and 3 from patients with inte stinal type gastric cancer) were characterized by vacA typing by PCR a nd DNA sequencing, Eighty-four of the 87 isolates were s1a/m1, one was s1b/m1, and two could not be typed. Moreover, all isolates in this st udy were cagA positive. There mere no distinct differences between the cytotoxin-producing strains and cytotoxin-nonproducing strains within the 0.73-kb middle region, Japanese strains were highly homologous, w ith more than 96% identity in this region, in which maximum divergence has been reported, In addition, there were no associations between th e specific vacA types and the level of in vitro cytotoxin activity or the clinical consequences, These results indicate that the cagA-positi ve, s1a/m1-type strains are common in japan, regardless of the vacA ph enotype or clinical outcome.