Restriction fragment length polymorphism of virulence genes cagA, vacA and ureAB of Helicobacter pylori strains isolated from Iranian patients with gastric ulcer and nonulcer disease

OBJECTIVE: To investigate the distribution of different genotypes of major virulence factors cagA, vacA and ureAB among Helicobacter pylori (H. pylori) strains isolated from patients with ulcerative and nonulcerative diseases.

METHODS: This study was performed in Clinical Microbiology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran, during November 2004 to October 2005. Sixty-five H. pylori strains, 30 from patients with gastric ulcer (ulcerative disease) and 35 from patients with gastritis (nonulcerative disease) were analyzed by polymerase chain reaction (PCR) to investigate the presence of cagA, vacA and ureAB genes. The amplified fragments were then digested with the restriction enzymes HaeIII (for ureAB) HinfI (for cagA) and HphI (for vacA).

RESULTS: We found a significantly higher prevalence of vacA-positive strains in ulcerative disease (UD) than that in nonulcerative disease (NUD) patients (p<0.05). Restriction fragment length polymorphism (RFLP) analysis revealed 2 different patterns for cagA gene. The prevalence of pattern &#946; with 3 bands was significantly higher in both groups of patients. HaeIII digestion resulted in a strictly homogeneous pattern for 83.33% of the vacA+ strains isolated from the patients with UD. This pattern was significantly associated with UD status (p<0.05). The ureAB polymorphism analysis revealed 10 distinguishable DNA banding patterns among them the pattern named ureAB 5a was the most prevalent (47.61%) in all isolates. No association between a specific DNA pattern and clinical disease was observed for cagA and ureAB (p>0.05).

CONCLUSION: It seems that in our patients, the presence of cagA gene may not necessarily be a risk factor for ulcer disease, while a homologous genotype of vacA appears to be associated with an increase risk of UD development. Lastly, despite the existence of a high degree of genomic variability within ureAB, conserved DNA banding profiles are distributed in our areas.