Detection Of Helicobacter Pylori Genotypes From Human Gastric Mucosa And Its Association With Gastric Diseases

PrefaceHelicobacter pylori(H.pylori)causes chronic infection in a large proportion of the world's population and is associated with the pathogenesis of gastritis, gastric and duodenal ulcers,mucosa-associated lymphoid tissue lymphoma and gastric cancer. Several methods such as histologic examination,the rapid urease test and culture, which can be used to detect H.pylori in gastric biopsy specimens. But histologic examination is dependent upon the experience and accuracy of the observers, when patch distribution of a low number of H.pylori in the stomach mucosa may result in a false negative;The rapid urease test requires a high density of H. pylori and anything that reduces the bacterial load may produce false negtive results; Athough culture proved a very successful method for detecting H.pylori in gastric biopsy specimens, the length of time required for the isolation of the organism and lower sensitivity are also seen to be a problem in routine clinical practice. In addition, almost half of the world's population suffered from H.pylori infection, but only some individuals developed gastric diseases with clinical symptoms. The reason for the phenomenon may be different pathogenicity of infected H.pylori.A rapid,accurate method of detecting H.pylori and its genotype is essential for proper patient management, and particularly for the eradication of the bacterial following treatment. Currently, to investigate the association between H.pylori infection and gastric dieases, some authors have detected H.pylori directly from infected gastric mucosa. Gunn MC et al reported that cagA gene was not associated with peptic ulcer using DNA extracted directly from biopsy specimens. David. Y.et al simulated mucosal biopsy by addig noninfected gastric mucosal tissues to H.pylori suspended. After 2h of incubation to enhance attachment and bacterial tissue interactions,DNA was extracted from the pellets by using the QIAamp tissue kit,PCR for vacA and cagA genotypes of H. pylori using DNA isolated from infected gastric biopsy specimens was approximately equal to genotypes using bacterial DNA from cultures. However, they didn't compare genotypes from gastric biopsy with that from cultures,which is lack of medical science evidence. Moreover, it is still unclear whether the method is easily influenced by other bacterials in the stomach mucosa or template DNA,and whether it accurately reflected actual condition of nature popution infected.ObjectiveTo identify the accordance level of H.pylori genotypes extracted from gastric mucosa with that isolated bacterium and investigate the feasibility of H.pylori detection directly from gastric mucosa and the relationship between H.pylori genotypes and gastric diseases.MethodA total of 217 cases diagnosed by pathology were involved in this study,which contain superficial gastritis 90 cases, ulcer and erosion 28 cases,atrophic gastritis 70cases, gastric cancer 29cases. Bacterim culture and DNA extraction were undertook from gastric mucosa respectively. UreB, cagA, vacA,iceA and baba2 genotypes were detected by PCR. x~2 or Fisher's exact test was used for analysis of data for difference areas. A P value of <0.05 was accepted as statistically significant. ResultThe concordance rate of ureB, cagA, vacAs1, vacAm1, vacAm2, iceA1, iceA2, baba2 genotypes were 74.23%,73.39%, 93.69%, 62.16%, 78.16%, 89.13%, 88.37% and 75% respectively using two different DNA specimens. The difference were not statistically significant(P>0.05). The distribution were no significant difference among different gastric diseases in ureB,cagA, vacAs1,vacAm1b, iceA1,iceA2 and baba2 genotypes(P>0.05). But the distribution frequency of vacAs1m1 strains in superficial gastritis(22.22%)was higher than that in atrophic gastritis (5.71%),the difference was statistically significant (x~2=8.416 P =0.004). The distribution frequency of vacAslm2 strains in atrophic gastritis(47.14%)was higher than that in superficial gastritis( 18.89%), the difference was statistically significant (X~2=13.336 P =0.000).ConclusionH.pylori can be rapid detected using DNA isolated directly from infected gastric mucosa. VacAs1m1 was associated with superficial gastritis and vacAs1m2 strains was associated with atrophic gastritis.