Correlation Of CagA, VacA And IceA Gene Polymorphism With Upper Gastrointestinal Diseases And Antibiotic Resistance Profiles Of Helicobacter Pylori Isolates

Helicobacter pylori is a spiral shaped microaerophilic Gram-negative rod that colonizes in human gastric mucosa. H. pylori is associated with antral gastritis, peptic ulcer disease(PUD) and even gastric carcinoma. The mechanisms by which H. pylori causes mucosal inflammation and damage are not well defined but probably involve both bacterial and host factors. The cagA, vac A and ice A are three important virulence genes of H. pylori, and they showed abundant genetic polymorphism in different individuals and different areas. The cagA gene encodes the Cag A protein. Sequence variations in the 3’region of the cagA impose a functional impact to the translated Cag A protein. The carboxy terminus(C-terminus) of Cag A may undergo polymorphisms to give different types of EPIYA motifs, which is associated with the outcome of gastrointestinal diseases. The vac A gene encodes a vacuolating cytotoxin presented in all strains, which comprises greater genetic variation regions such as s m and i. The pathogenicity of the bacterium is decided by the mosaic combination allelic types. The ice A gene has two alleles: ice A1 and ice A2. The presence of ice A1 allele is strongly associated with peptic ulcer disease and the increased content of IL-8 in gastric mucous. Investigating the prevalence difference of virulence genes of H. pylori isolated from patients with different gastrointestinal diseases which is important to determine the prognosis of patients and clarify the pathogenesis of H. pylori.Gastric biopsies from 298 patients referred to gastroscopy were collected but H. pylori were isolated in 20.1% of them(60/298). The isolation rate of H. pylori in peptic ulcer disease(PUD) patients is higher than that in non-peptic ulcer dyspepsia(NUD)patients(P<0.05).The cagA gene was detected in 90%(54/60)strains.Out of 26 sequenced isolates,there were East Asian- type EPIYA :ABD(84.6%, 22/26), ABBD(3.8%, 1/60) and Western-type EPIYA :ABC(7.7%,2/26), BC(3.8%,1/26). EPIYA motif sequencesfrom 93 H. pylori reference strains worldwide and 26 sequences produced in the present work were used to construct a phylogenetic tree. The phylogenetic tree based on the DNA sequences of cagA was divided into two major groups, a Western group and an East Asian group, and there is no regional distribution difference in isolates. It may be related to population flow and cross-infection.The vac A s-region was amplified in all 60 H. pylori strains: 86.7%(50/60)were identified as s1 and 13.3%(8/60)as s2. The vac A s1 c subtype was detected in 33.3%(20/60)which was the majority. All strains were typed by vac A m-region, resulting in 56.7%(34/60)with m2 allele and 43.3%(26/60)with m1 allele. A significant association was found among m1 allele and PUD as well as m2 allele with NUD(P<0.05).Allele i1 was detected in 78.3%(47/60)and i2 in 21.7%(13/60). In this study, vac A genotypes s1m1i1, s1m2i1, s2m2i2 and s1m2i2 were determined in43.3%(26/60), 35%(21/60), 13.3%(8/60)and 8.3%(5/60)of the isolated H.pylori respectively. A significant association was found among s1m1i1 genetype and PUD.The ice A1 subtype was detected in 80%(48/60)and ice A2 in 16.7%(10/60).3.3%strains were identified with both ice A alleles(2/60)and no distribution difference was found in diseases. The presence of cagA+/vac As1m1i1/ice A1 were detected in 35%(18/60)of all isolated strains, the ratio in PUD(50%,13/26) was higher than that in NUD(23.5%, 8/34); The presence of cagA+/vac As1m21i1/ice A1 were detected in28.3%(17/60)of all isolated strains, the ratio in NUD(41.2%,14/34) was higher than that in PUD(11.5%, 3/26). It indicated that significant association was observed between cagA+/vac As1m1i1/ice A1 genetype and PUD as well as cagA+/vac As1m21i1 ice A1 genetype and NUD.In conclusion, this study is meaningful of expounding the connection of Hp virulence genes polymorphism with different diseases and the relationship between Hp genetic diversity and its geographical aggregation.Individual infected H. pylori has more chance to develope to serious diseases such as gastric ulcer and gastric carcinoma. So it is necessary and urgent to eradicate H.pylori early. But in recent years, the eradication rate of H. pylori has reduced to below80% in many parts of the world which was mainly due to H. pylori resistance tocommonly used antibiotics. The levels of antibiotic resistant between different regions are discrepant because of the different customs of antibiotics prescribed.In this study 6.6% of isolates were resistant to amoxicillin, 40% to metronidazole and 45% to clarithromycin. As the Maastricht IV consensus suggested among the commonly used antibiotics, amoxicillin is still a good choice of treatment, while the combined use of clarithromycin and metronidazole should not be in the first place.The resistance rate of tinidazole, tetracycline, levofloxacin and furazolidone were46.7%, 31.7%, 30% and 20% respectively. Multidrug resistance was observed in 35%of isolates: triple resistance were 10%, Quadruple resistance were 15%, quintuple resistance were 10%. Antibiotics should be chosen based on antibiotic susceptibility results for multi-drug resistant strains.The study of antibiotics resistance provides the basis for developing individualized treatment program. It is helpful to improve the H. pylori eradication rate, reduce the risk of gastric cancer, decrease the suffering and lighten the financial burden of patients.