Helicobacter pylori: comparison of DNA fingerprints provides evidence for intrafamilial infection

Although a high prevalence of antibodies to Helicobacter pylori has been documented within families, culture and DNA typing of strains from infected children and their parents has not been evaluated. This study aimed to analyse H pylori infection within family groups. Endoscopy, gastric biopsy, and H pylori culture were performed on all eight parents of four children who presented with dyspepsia and who had a positive H pylori culture. All biopsy specimens were cultured on Columbia based blood agar under microaerophilic conditions for four days. The DNA from each strain was extracted and electrophoretic patterns were compared after digestion with restriction endonucleases Hae III or Hind III. Ribotyping using a biotinylated cDNA probe prepared from 16S and 23S rRNA of H pylori NCTC 11638 was also used. Seven of the parents were positive for H pylori on urease testing, histology, and on culture. DNA typing showed the same or a similar strain to be present in at least two family members in three of the four family groups. In family 1, the mother, father, and child all had an identical strain; in family 2, father and son had a similar related strain; father and mother had the same strain in family 3; and all strains were unique in family 4. These data provide evidence for either intrafamilial cross infection or a common source of infection within family groups.