Individual hosts carry H. pylori isolates with different cagA features - motifs and copy number.

BACKGROUND: H. pylori strains with different genetic contents may infect different or an individual human host. Genetic diversity of cagA is thought to contribute to differences in H. pylori strains pathogenicity. In this study, diversity of cagA genotype, EPIYA motif and copy number was assessed in H. pylori single colonies isolated from individual patients.

MATERIALS AND METHODS: Gastric biopsies from 14H. pylori-positive dyspeptic patients were cultured on selective brucella blood agar and incubated at 37 °C under microaerobic conditions. Four single colonies were obtained from each biopsy subculture on brucella blood agar under similar incubation condition. Presence of cagA and types of EPIYA motifs was determined by polymerase chain reaction (PCR) and cagA copy number by quantitative real-time (RT) PCR.

RESULTS: Single colonies of 5 patients showed no variation in cagA genotype, EPIYA motif and copy number. Out of the remaining 9 patients, 1 patient showed presence or absence of cagA gene, 2 patients had mixed EPIYA motifs, 2 patients had different cagA copy number, 1 patient showed absence or presence of cagA and mixed motifs, 2 patients had cagA genes with different nucleotide sequences, 1 patient showed presence or absence of cagA and difference in cagA nucleotide sequence. Four isolates that contained multiple copies of cagA, carried EPIYA-ABC motif.

CONCLUSION: Genetic diversity of cagA among single colonies isolated from individual patients represents evidence that gastric mucosa of every individual is colonized with a specific and heterogeneous population of H. pylori. Future studies on patients in different disease groups may elucidate the role of mixed populations of H. pylori in development of gastric diseases.