Association among H. pylori virulence markers dupA, cagA and vacA in Brazilian patients

Background:Only a few Helicobacter pylori-infected individuals develop severe gastric diseases and virulence factors of H. pyloriappear to be involved in such clinical outcomes. Duodenal ulcer promoting gene A (dupA) is a novel virulence factor ofHelicobacter pylori that is associated with duodenal ulcer development and reduced risk for gastric carcinoma in some populations. The aims of the present study were to determine the presence ofdupA gene and evaluate the association amongdupA and other virulence factors includingcagA and vacA in Brazilian patients. Gastric biopsies were obtained from 205 dyspeptic patients (100 children and 105 adults). DNA was extracted and analyzed for the presence of H. pylori and its virulence factors using the polymerase chain reaction method.Results:Patients with gastritis tested positive for H. pylori more frequently. The dupA gene was detected in 41.5% of them (85/205); cagA gene was found in 98 isolates (47.8%) andvacA genotype s1/m1 in 50.2%, s1/m2 in 8.3%, s2/m2 in 36.6%, s2/m1 in 0.5% and s1/s2/m1/m2 in 4.4%. We also verified a significant association between cagA and dupA genes [p = 0.0003, relative risk (RR) 1.73 and confidence interval [CI] = 1.3-2.3]. The genotypes s1/m1 were also associated with dupA gene (p = 0.0001, RR: 1.72 and CI: 1.3-2.2). The same associations were found when analyzing pediatric and adult groups of patients individually.Conclusion:Ours results suggest that dupA is highly frequent in Brazilian patients and is associated with cagA gene andvacA s1/m1 genotype, and it may be considered an important virulence factor in the development of gastric diseases in adults or children.

研究背景：仅少数幽门螺杆菌（Helicobacter pylori）感染者会发展为严重胃部疾病，而幽门螺杆菌的毒力因子似乎与这类临床结局密切相关。十二指肠溃疡促进基因A（dupA）是一种新型幽门螺杆菌毒力因子，在部分人群中与十二指肠溃疡的发生相关，且可降低胃癌发病风险。本研究的目的为检测dupA基因的存在情况，并评估巴西患者中dupA与其他毒力因子（包括cagA和vacA）之间的关联。本研究从205例消化不良患者（100名儿童、105名成人）中获取胃活检组织，提取DNA后采用聚合酶链式反应（polymerase chain reaction，PCR）方法检测幽门螺杆菌及其毒力因子的存在。

研究结果：胃炎患者的幽门螺杆菌检测阳性率更高。在全部受试者中，dupA基因的检出率为41.5%（85/205）；cagA基因在98株分离株中被检出，检出率为47.8%；vacA基因型分布如下：s1/m1型占50.2%，s1/m2型占8.3%，s2/m2型占36.6%，s2/m1型占0.5%，s1/s2/m1/m2型占4.4%。本研究还证实cagA与dupA基因之间存在显著关联[P=0.0003，相对危险度（relative risk，RR）=1.73，置信区间（confidence interval，CI）=1.3~2.3]。s1/m1型vacA基因型同样与dupA基因存在显著关联（P=0.0001，RR=1.72，CI=1.3~2.2）。分别对儿童组与成人组患者进行单独分析时，也得到了一致的关联结果。

研究结论：本研究结果显示，dupA基因在巴西患者中具有较高的检出率，且与cagA基因及vacA s1/m1基因型存在关联，提示其可作为成人或儿童胃部疾病发生过程中的重要毒力因子。