Clinical implications and prevalence of cagA, cagE and cagT genes in the pathogenicity island of Helicobacter pylori strains isolated from Shanghai patients

OBJECTIVE: The cag pathogenicity island (cag PAI) has been reported to be the major factor controlling the virulence of Helicobacter pylori and has been associated with clinical outcome after H. pylori infection. The role of cag PAI genes in the pathogenicity of H. pylori infection remains to be established. The aim of the present study was to investigate: (i) the prevalence of cagA, cagE and cagT, the representative genes of cag PAI status, in H. pylori strains isolated from patients with various gastroduodenal diseases in the Shanghai region; and (ii) the relationship between the presence of these genes and different gastroduodenal diseases. METHODS: Ninety-nine H. pylori strains were isolated from patients with chronic superficial gastritis (17), chronic atrophic gastritis (21), gastric ulcers (19), duodenal ulcers (23) and gastric cancer (19). The prevalence of the cagA, cagE, and cagT genes was studied in these strains by using the polymerase chain reaction (PCR) method. RESULTS: The total prevalences of cagA, cagE and cagT genes were 84.8, 99 and 84.8%, respectively, in the 99 strains of H. pylori tested. There was no significant difference in the prevalence of cagA, cagE or cagT in H. pylori isolated from different gastroduodenal diseases (all P > 0.05). Of the 98 cagE-positive isolates, 14 (14.3%) were cagA negative. Only one of 99 isolates was negative for both cagE and cagA. Of the 84 cagT-positive strains, two were cagA negative. CONCLUSIONS: Most of the H. pylori isolates in the Shanghai region may have intact cag PAI. It was found that cagE, but not cagA, could be used as a marker for the presence of cag PAI. There is no correlation between the integrity of cag PAI and the clinical outcome after infection with H. pylori.