DNA-DNA hybridization demonstrates apparent genetic differences betweenHelicobacter pylori from patients with duodenal ulcer and asymptomatic gastritis

We asked whether different clinical outcomes ofHelicobacter pylori infection might be a reflection of genetic differences in infecting organisms. Using DNA-DNA hybridization we examined whether hybridization levels groupedH. pylori isolates corresponding to the type of disease (gastric ulcer, duodenal ulcer, asymptomatic gastritis) from which they were recovered. Target DNAs were prepared fromH. pylori strains cultured from gastric biopsy specimens of 25 patients; 5 with gastric ulcers, 9 with duodenal ulcers, and 11 from asymptomatic volunteers endoscopically proven not to have peptic ulcer disease. DNA-DNA hybridization was performed with whole genomic probes made from an isolate from each of the three disease categories. Using a DNA probe from an isolate from a duodenal ulcer patient, we found that isolates from patients with duodenal ulcer and nonulcer gastritis yielded significant differences in levels of hybridization. The levels of hybridization of DNA fromH. pylori isolates from duodenal ulcer patients, gastric ulcer patients and nonulcer gastritis controls were 85.5%±7%, 83%±3%, and 78.3%±5%, respectively (mean±sd), and the difference between the hybridization levels obtained with duodenal ulcer and nonulcer control target DNAs was statistically significant (P=0.025). These data suggest that the outcome of infection (eg, ulcer or no ulcer) may be due to virulence factors encoded by genomic DNA. If such differences exist, it should be possible to produce probes that would identify the ulcer virulence gene(s) and clearly distinguish between ulcerogenic and nonulcerogenic strains ofH. pylori.This work was supported by Veterans Affairs; by grant DK 39919 from the National Institute of Diabetes and Digestive and Kidney Diseases and by the generous support of Hilda Schwartz.