Purpose: Chronic Helicobacter pylori  infection causes peptic ulcers in a subpopulation of individuals and is a risk factor for the development of gastric cancer. Multiple infections and heteroresistant H. pylori  contribute to poor treatment efficacy. Here, we investigated the extent of genetic diversity among H. pylori  strains within a given host and its influence on the results of antibiotic (metronidazole, levofloxacin, clarithromycin, amoxicillin, and tetracycline) susceptibility testing.
Materials and Methods: Gastric mucosa biopsy samples were obtained from patients with gastric disorders, including 48 H. pylori  positive patients, who were never previously treated for H. pylori  infection. Five potential H. pylori  colonies isolated from each sample were subcultured for enrichment. Enriched H. pylori  colonies were identified through Gram staining and assays for urease, oxidase, and catalase. For each H. pylori  monoclonal colony, the antibiotic susceptibility was assessed, genomic DNA was sequenced, and the cytotoxin-associated gene A  (cagA ) genotype was verified. Co-infection with multiple H. pylori  strains was determined using random amplified polymorphic DNA (RAPD)-polymerase chain reaction (PCR).
Results: Thirteen gastric mucosa biopsy samples were positive for H. pylori . Five monoclonal strains isolated from each of these 13 patients were identified as H. pylori . RAPD-PCR indicated that intra-patient monoclonal strains of H. pylori  in 10 of the 13 samples exhibited heterogeneity. Among the 13 patients, intra-patient monoclonal strains isolated from 4 patients had identical cagA  genotype, whereas intra-patient monoclonal strains isolated from the other 9 patients harbored more than one cagA  genotype. The antibiotic susceptibility of five intra-patient monoclonal strains from seven patients was inconsistent.
Conclusion: The existence of heterogeneous H. pylori  strains with resistance to different drugs and virulence were common within the gastric mucosa of an individual patient.
Keywords: Helicobacter pylori , heterogeneity, antibiotic resistance, cagA  typing