Background: Diversity of DNA among H. pylori strains isolated from different patients can serve as a useful marker for differentiating strains. DNA profiles of H. pylori obtained from sequential gastric biopsies were identical in most patients indicating that a given strain can persist from months to years. Patients colonized with more than two strains isolated mainly from different anatomical sites have been reported. This work examined whether the gastric antrum of patients with dyspepsia is colonized by single or multiple strains of H. pylori as well as the in vitro competition of different strains of H. pylori.
Materials and methods: Two antral biopsy specimens from each of the 124 patients were cultured for H. pylori. DNA fingerprinting of H. pylori isolates was performed using random amplified polymorphic DNA (RAPD) analysis. To elucidate the possible interaction among H. pylori isolates, bacterial populations of two H. pylori strains cogrown in broth medium over 21 days were enumerated and DNA fingerprinting was compared.
Results: A total of 58 patients showed the presence of H. pylori in both antral specimens, while five patients had H. pylori in only one of the two samples. These 58 patients were shown to harbor a single strain of H. pylori as analyzed by RAPD fingerprinting. In vitro studies of bacterial interaction of two different strains of H. pylori showed growth competition resulting in the predominance of a single strain.
Conclusions: The results support the concept that a single strain predominates in the gastric antrum site of patients studied.