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Diversity in cag pathogenicity island (cag PAI) of Helicobacter pylori isolates from North and South Indian populations

¹ School of Biotechnology, Banaras Hindu University, Varanasi;

² Department of Gastroenterology, Institute of Medical Sciences,

³ E-mail: kasokbt{at}rediffmail.com

Received June 22, 2009
Accepted October 7, 2009

The cag pathogenicity island (cagPAI) has been reported to be the major virulence determinant of Helicobacter pylori-related diseases. In the present study diversity in cagA gene and integrity of cagPAI in one hundred fifty eight H. pylori strains of Varanasi (North India) and Hyderabad (South India) were studied by amplifying cagA gene (ca 3.5 kb) followed by PCR-RFLP analysis. Results revealed significant differences in cagA gene and the integrity of cagPAI between North and South Indian isolates. Out of 158 isolates, 40 (34.8%) from Varanasi and 20 (46.5%) of Hyderabad were found to carry intact cagPAI. Partially deleted cagPAI was present in 75 (65.2%) isolates of Varanasi and 23 (53.5%) Hyderabad. None of the isolates showed complete deletion of cagPAI. Differences in cagA 5' and cagA 3' region were also noted and eleven isolates (8 from Varanasi and 3 from Hyderabad) which were found cagA negative with primers for 5' region turned out to be cagA positive with primers of 3' variable region. It is tentatively concluded that the 3' variable region may be a better marker for cagA typing. Results of PCR-RFLP of cagA gene (3.5 kb) showed 29 distinguishable digestion patterns and cluster analysis of RFLP types placed all the 32 isolates into five groups. Our results demonstrate that significant differences in cagPAI occur among isolates of North and South India and RFLP of cagA could be employed for elucidating genetic variations among various isolates of H. pylori.