Genetic variation of Helicobacter pylori in the oral cavity and stomach detected using thymine adenine cloning in children with chronic gastritis.

OBJECTIVE

To investigate the DNA sequence variations of Helicobacter pylori in the oral cavities and stomachs of children with chronic gastritis.

METHODS

Dental plaques and gargle on 235 patients were obtained before gastroscopy. Gastric H. pylori infection was diagnosed using rapid urease test or Giemsa staining. H. pylori 16S rDNA and CagA gene were analyzed using PCR methods. Thymine adenine cloning-based sequencing was performed in patients with CagA gene positive from oral cavities. The sequence alignments and V1 variable region were evaluated by comparison with the sequence of the standard H. pylori 26695 strain.

RESULTS

Totally, 46 out of the 235 patients were positive for gastric H. pylori infection. Of the 46 patients, 26 cases had amplified H. pylori 16S rDNA in both oral (plaque and gargle) and gastric samples. Of the 26 cases, 12 patients (46.1%) were positive for the H. pylori CagA gene in the oral samples, which was significantly lower than that in the gastric mucosa (80.8%; P = 0.010). The homology of the complete sequence alignment ranged from 74.0% to 92.1% in the oral and gastric samples. The V1 region alleles (positions 75-99) had 7-22 polymorphisms (homology from 12.0% to 72.0%) in 11 patients between the oral and gastric samples, but had 100% homology in 1 patient.

CONCLUSIONS

Our study found that distinct H. pylori strains exist in the oral cavities of children, but we would not support the hypothesis that H. pylori in the oral cavities is an important reservoir of gastric H. pylori infections in children.