[Detection of Helicobacter pylori in human saliva by using nested polymerase chain reaction]

Abstract

Epidemiologic studies suggest person to person spread of Helicobacter pylori (H. pylori), but the exact mechanism is unknown. Spread through oral secretions has been suggested, however, it has proved very difficult to grow the organism from areas outside the stomach. A nested polymerase chain reaction (N-PCR) for the specific detection of H. pylori was developed with two primer pairs (nested primers) derived from the urease gene A of H. pylori. The N-PCR could detect all 21 H. pylori strains, including 20 isolated strains and 1 reference strain NCTC 14126, but could not detect other bacterial species, showing the N-PCR assay to be 100% specific. Tenfold serial dilution experiments revealed the detection of as little as 0.1 fg DNA by N-PCR. To evaluate the PCR assay for clinical samples, gastric biopsy and aspirate specimens were tested by N-PCR, and the results were compared with those of culture, urease test and histologic examination (reference standard, RS). Among 57 biopsy specimens, H. pylori sequence was detected by PCR in 39 of 39 (100%) positive tissues and in none of 18 negative tissues. H-pylori was detected in saliva of 11 out of 19 cases in which H. pylori was positive in gastric mucosa by PCR. Whereas, PCR was positive in saliva of only one out of 8 cases in which H. pylori was negative in gastric mucosa. Six gastric aspirate specimens were positive by N-PCR. PCR is an accurate and sensitive method that can detect the presence of H. pylori without the need of culture.