Infection with cagA-positive H. pylori strains is linked to an increased risk for gastric diseases, including gastric cancer. Recent evidence indicates that dynamic expansion of cagA copy numbers may serve as a novel mechanism to enhance disease development. In this study, presence of H. pylori strains carrying multiple copies of cagA gene were assessed in isolates from individual patients using PCR method.

Methods: In 12 H. pylori- positive patients, four single colonies were isolated from the primary H. pylori culture plates. In each isolate, cagA status was determined by PCR amplification of a 298 bp fragment. Next, in all cagA-positive H. pylori isolates, the possibility of the presence of adjacent multiple cagA copies was examined by PCR using appropriate primers.

Results: In two patients, all isolates were cagA negative. Five out of ten patients carried H. pylori isolates with more than one cagA copy number; In two patients, one isolate had multiple cagA copy number and three isolates had single copy, in two patients, two isolates had multiple copy of and two isolates had single copy and in one patient, three isolates had multiple copy and one isolate had single copy.

Discussion: It has been demonstrated that isolates harboring more cagA copies produced more CagA, thus enhancing toxicity to host cells. Results of this study showed that H. pylori isolates with single and multiple cagA copy numbers could be simultaneously present in a single host. co-existence of H. pylori isolates with different cagA copy number in a same stomach is an important phenomenon which must assessed in large number of patients to draw a correlation with clinical outcomes.