Prevalence of Vacuolating Cytotoxin Production and Distribution of Distinct vacA Alleles in Helicobacter pylori from China

Studies of Helicobacter pylori from the West have linked production of vacuolating cytotoxin and a particular signal sequence (s1a) allele of the underlying vacA gene to peptic ulcer disease (PUD). Among Chinese H. pylori, most isolates from both PUD and gastritis patients were toxigenic (35/46 and 29/35, respectively). Polymerase chain reaction and DNA sequencing showed that 95 of 96 isolates carried vacA s1a alleles. In the mid-region, 78 of 96 isolates carried m2; 14 were m1-like but only 87% identical (DNA-level) to classical m1 and were designated m1b; the other 4 were unusual hybrids (m1b-type proximal, m2-type distal). Isolates with m1b and m1b-m2 alleles produced higher levels of vacuolating activity than did isolates with m2 alleles (P < .01). There was no association between any vacA allele and disease. These results suggest that the composition of H. pylori gene pools varies geographically and that other as-yet-unknown polymorphic H. pylori genes are important in PUD.