Helicobacter pylori in the oral cavity: High prevalence and great DNA diversity

To test the hypothesis that Helicobacter pylori may be transmitted by the o ral-oral route, we applied nested PCR and DNA sequencing to detect and anal yze H. pylori DNA in the oral cavity of 20 adult patients undergoing endosc opy. Dental plaques of molars, premolars, and incisors and saliva were coll ected. Additional paraffin-embedded gastric biopsies were analyzed in four patients. Two sets of highly sensitive and specific primers, EHC-U/EHC-L an d ET5-U/ET-5L directed to a 860-bp fragment of H. pylori DNA, were used in the nested PCR. Eight patients had an active infection in the stomach deter mined with the [C-13]urea breath test and the other 12 were negative. Neste d PCR showed that all 20 subjects (100%) were positive for H. pylori in the oral cavity. DNA sequencing demonstrated that all tested PCR products of t he expected size from the oral samples have more than 97% identity with tha t from H. pylori type strain ATCC 43629, However, sequences differed in ora l samples from different subjects as well as between different oral locatio ns and gastric biopsies within the same individuals. In conclusion, the ora l cavity may be a permanent reservoir for H. pylori and can harbor multiple H. pylori strains at the same time.