Gene Typing Of Helicobacter Pylori Strains In China

Objective To study the gene typing of Helicobacter pylori strains in China.Methods A total of 119 H.pylori strains were isolated from 7 different geographic regions(Beijing, Heilongjiang, Yantai, Zhejiang, Hubei, Xi'an and Yunnan) in China and different gastro-duodenal diseases(Chronic gastritis, peptic ulcer, gastric cancer and functional dyspepsia).7 housekeeping genes (atpA, efp, mutY, ppa, trpC, urel and yphC) and one virulence-associated gene(vacA) were analyzed by the application of multilocus sequence typing (MLST) method to obtain the allelic profile and the sequence type (ST) of the strains, and compared with the information of world-wide strains in the HP MLST database. Softwares BURST (Based Upon Related Sequence types), START2(Sequence Type Analysis and Recombinational Tests, version 2) and MEGA4.0(Molecular Evolutionary Genetics Analysis, version 4.0) were applicated to classify the strains as clonal complex, calculate the Index of Association(IA), and build the phylogenetic tree, respectively. vacA and its alleles were identified according to the length of the PCR products with DNA electrophoresis. The distributions of the vacA alleles were statistically analyzed by the software SPSS(version 13.0) and cluster analyzed by the software Mev₄₀ (Multiple Experiment Viewer, TIGR).Result A total of 107 STs were identified by MLST, which had not been reported in the HP MLST database.119 H.pylori strains were divided into three complax and others were singletons. The software START2 recombination analysis showed that the IA of 107 STs was 2.1398, the Mean trial variance was 0.0074, and the Max trial variance was 0.0081. Software MEGA4.0 distributed the 119 Chinese H.pylori isolates in 3 ancestors. 111 isolates were distributed in hpEastAsia,6 isolates in hpEurope and 2 isolates in hpAsia2. The alleles in vacA dominantly belonged to sla, m2 and il in the tested strains. The distribution appeared to be 97.5%(116/119), 68.9%(82/119) and 91.6%(109/119), respectively. The mlb allele appeared to be 26.1%(31/119). slb but mla were not found. The major vacA recombination was sla/m2/il, reaching to 62.2%. The second one was sla/mlb/il (25.2%,30/119). No association was found between the distribution of sla allele with 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 difference 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. One isolate of 119 was distributed in a group, eight isolates in another group, and the rest of the strains clustered into the largest group.Conclutions In this study, most of the H.pylori strains isolated in China were originated in hpEastAsia, very small parts belonged to hpAsia2 and hpEurope, but have not been found the strains of African origin. 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. H.pylori strains isolated in China were associated to the geographic regions, but no obvious correlation with the disease.