EVALUATION OF THE POLYMERASE CHAIN-REACTION FOR DETECTING THE UREASE-C GENE OF HELICOBACTER-PYLORI IN GASTRIC BIOPSY SAMPLES AND DENTAL PLAQUE

A polymerase chain reaction (PCR) assay with oligonucleotide primers h omologous to a portion of the urease C gene of Helicobacter pylori was evaluated for specificity with pure DNA and biopsy material. The assa y was used to test for the presence of the organism in dental plaque. The species specificity of detection was confirmed by ensuring that th e primers did not amplify DNA extracts from H.cinaedi, H.felis, H.fenn elliae, H.mustelae and H.nemestpinne. Sixty-two gastric biopsy samples collected from 14 patients (antrum, body and duodenal sites) were cul tured and PCR was performed on the samples after culture. Primer sites were conserved in genomically diverse strains. Samples prepared by si ngle-step heat lysis of bacterial cells and biopsy material did not in hibit PCR. The overall specificity was 96% irrespective of genotype. H .pylori was not cultured from dental plaque (15 patients), neither was H.pylori DNA detected by PCR in either urea breath test-positive or - negative individuals. The results showed that primer pair sequences wi thin the urease C gene are conserved in most strains and provide an ac curate basis for detecting H.pylori. As the PCR assay was not inhibite d and did not yield false positive results with crude extracts from or ganisms or in the presence of biopsy material, its value as a diagnost ic test was confirmed.