The characteristic structure and classification of cag pathogenicity island in Chinese Helicobacter pylori strains

Objective To investigate the characteristic structure of cag pathogenicity island (PAI), and the significance classified by the characteristic structure of cag PAI split in Chinese H.pylori strains. Methods cagA, cagⅠ, cagⅡ, conjunction of cagⅠ and cagⅡ and IS 605 were tested by polymerase chain reaction (PCR) in 107 H.pylori strains isolated from Chinese patients. Results The positive rate was 95.3% in cag PAI, 92.5% in cagA, 86.9% in cagⅠ, and 66.4% in cagⅡ. There was no statistical dif ference among chronic gastritis, peptic ulcer and gastric carcinoma in the detectable rate of cag PAI, or cagA, or cagⅠ, or cagⅡ ( P 0.05). The products of conjunction of cagⅠ and cagⅡ were found only in 5 strains. The detectable rate of continuous cag PAI was much higher in duodenal ulcer than in chronic gastritis ( P 0.01 ). The positive rate between cagⅠ and cagⅡ was markedly different in patients with chronic gastritis ( P 0.05). One strain which was only cagA positive and other parts of cag PAI was negative was found. The detectable rate of IS 605 was lower in duodenal ulcer than in chronic gastritis ( P 0.05). The amplified fragment of IS 605 in one strain from gastric carcinoma was about 1 580 bp, which was much longer than that in other strains. Conclusion Our results indicated that the presentation of cag PAI were predominant in Chinese H.pylori strains. Some new structure of cag PAI were found. The variety of structure of cag PAI might be related to virulence of H.pylori . It was suggested that H.pylori could be classified as different virulent groups according to the difference of structure of cag PAI.