中国人感染幽门螺杆菌的基因分型及其临床意义

Distribution of cagA gene in Helicobacter pylori and its clinical significance

目的：研究细胞毒素相关基因Ａ（ｃａｇＡ）在幽门螺杆菌（Ｈｐ）菌株中的分布，并初步探讨其应用价值。方法：采用特异性引物扩增ＨｐｃａｇＡ的２９７ｂｐ片段，对７４株临床分离Ｈｐ菌株进行ＰＣＲ分型，并与直接检测胃粘膜中ｃａｇＡ结果进行比较。同时收集患者的胃镜诊断及胃窦病理资料，分析ｃａｇＡ与不同上消化道疾病及胃粘膜局部形态学改变的关系。结果：９０．５％的Ｈｐ菌株含ｃａｇＡ（ｃａｇＡ＋，Ⅰ型），其中消化性溃疡患者Ｈｐ菌株ｃａｇＡ携带率（９４．９％）高于慢性胃炎患者（８５．７％），但无显著差异。病理资料显示Ⅰ，Ⅱ型（ｃａｇＡ－）菌株均可引起胃窦的慢性炎症，但严重程度Ⅱ型菌株高于Ⅰ型（Ｐ＜０．０５），二者在致活动性胃炎、肠上皮化生、胃粘膜萎缩及淋巴滤泡形成方面差异不显著。ＰＣＲ直接检测胃粘膜与检测Ｈｐ菌株中ｃａｇＡ的结果相近似。结论：中国人感染ＨｐⅠ型菌株比例较西方国家高，但ｃａｇＡ尚不能作为区分Ｈｐ感染致不同消化道疾病的单一指标。

Objective: To study the distribution of cagA gene in Helicobacter pylori (Hp) and its clinical significance. Methods: Typing of Hp was determined by PCR in 74 clinical isolates by using one primer set for the cagA gene. Results: The prevalence of cagA gene in Hp isolates was 90.5%,the positive rate of cagA gene in peptic ulcer patients being 94.9%, higher than that in chronic gastritis patients (85.7%), though the difference was insignificant. Both typeⅠ (cagA +)and typeⅡ (cagA -) isolates led to chronic inflammation of antrum, though the former caused more severe inflammation than the latter. There was no significant difference in severity of active gastritis, intestinal metaplasia, atrophy and lymph folliciles. Conclusion: The high prevalence of cagA gene in Hp isolates from native patients indicates that cagA gene is common in Hp strains, and therefore, is not reliable as a single marker for the discrimination of Hp strains with respect to a specific disease.