[Polymorphism of Helicobacter pylori vacA, isolated in China]

To understand the polymorphism of Helicobacter pylori (H. pylori) vacA alleles in China.

A total of 119 H. pylori strains were isolated from different gastro-duodenal diseases in 7 different geographic regions in China. vacA and its alleles were identified according to the length of PCR products with DNA electrophoresis. The distributions of vacA alleles were statistically analyzed. The core fragment of vacA was sequentially analyzed by software MEGA4.0.

The alleles in vacA dominantly belonged to s1a, m2 and i1 in the tested strains. The distribution appeared to be 97.5% (116/119), 68.9% (82/119) and 91.6% (109/119), respectively. The m1b allele appeared to be 26.1% (31/119). s1b and m1a were not found. The major vacA recombination was between s1a/m2/i1 and 62.2%, followed by s1a/m1b/i1 (25.2%, 30/119). No association was found between the distribution of s1a allele and the clinical outcome, as well as the geographical regions (P > 0.05). However, the distribution of m alleles showed significant difference both among the types of disease and the geographic regions (P < 0.01). The present of i alleles did not show significant differences among disease patterns, but had significant differences between different geographic groups (P < 0.01). Three clusters were identified among these 119 isolates according to the DNA sequence of vacA.

s1a/m2/i1 appeared to be the main allele in H. pylori vacA isolates from China in this study. The distribution of m alleles in vacA was correlated both to the regions and the disease patterns. The presence of i allele was associated to the regions but not the disease patterns.