Camorlinga-Ponce M, Romo C, González-Valencia G, Muñoz O, Torres J
Unidad de Investigación en Enfermedades Infecciosas, Hospital de Pediatría, Instituto Mexicano del Seguro Social, Mexico.
J Clin Pathol. 2004 Aug;57(8):822-8. doi: 10.1136/jcp.2004.017087.
The cagA gene is a marker for the presence of the cag pathogenicity island, and the presence of cagA positive strains of Helicobacter pylori can identify individuals with a higher risk of developing gastrointestinal diseases.
To study the interaction between H. pylori cagA(+) and cagA(-) strains and the gastric mucosa.
Patients with H. pylori associated gastritis and peptic ulcers were studied. Biopsies were obtained from the antrum, corpus, fundus, and incisura for H pylori culture, and for in situ hybridisation studies. From each biopsy, multiple single H. pylori colonies were isolated and propagated for DNA isolation, and cagA was detected by the polymerase chain reaction (PCR). For in situ detection of H. pylori an oligonucleotide specific for an H. pylori common antigen and an oligonucleotide specific for cagA were used as probes. Biotinylated probes were incubated with biopsy sections, developed with streptavidin-horseradish peroxidase, and amplified with the tyramide system.
PCR results for cagA in isolated colonies confirmed the in situ hydridisation studies. In situ hybridisation identified cagA(+) bacteria in patients with cagA(+) isolates; cagA(-) bacteria in patients with cagA(-) isolates, and cagA(+) and cagA (-) bacteria in patients with both cagA(+) and cagA(-) isolates. CagA(-) bacteria usually colonised the mucous gel or the apical epithelial surface, whereas cagA(+) bacteria colonised the immediate vicinity of epithelial cells or the intercellular spaces.
These results document a different in vivo interaction between H. pylori cagA(+) or cagA(-) strains and the gastric mucosa.
cagA基因是细胞毒素相关基因致病岛（cag致病岛）存在的标志物，幽门螺杆菌cagA阳性菌株的存在可识别出患胃肠疾病风险较高的个体。
研究幽门螺杆菌cagA（+）和cagA（-）菌株与胃黏膜之间的相互作用。
对幽门螺杆菌相关性胃炎和消化性溃疡患者进行研究。从胃窦、胃体、胃底和胃切迹处获取活检组织用于幽门螺杆菌培养和原位杂交研究。从每个活检组织中分离出多个单个幽门螺杆菌菌落并进行传代培养以提取DNA，通过聚合酶链反应（PCR）检测cagA。为了原位检测幽门螺杆菌，使用针对幽门螺杆菌共同抗原的寡核苷酸和针对cagA的寡核苷酸作为探针。将生物素化的探针与活检切片孵育，用链霉亲和素-辣根过氧化物酶显色，并通过酪胺系统进行放大。
分离菌落中cagA的PCR结果证实了原位杂交研究。原位杂交在cagA（+）分离株患者中鉴定出cagA（+）细菌；在cagA（-）分离株患者中鉴定出cagA（-）细菌，在同时有cagA（+）和cagA（-）分离株的患者中鉴定出cagA（+）和cagA（-）细菌。cagA（-）细菌通常定植于黏液凝胶或顶端上皮表面，而cagA（+）细菌定植于上皮细胞紧邻区域或细胞间隙。
这些结果证明了幽门螺杆菌cagA（+）或cagA（-）菌株与胃黏膜之间在体内存在不同的相互作用。
