Sensitive detection of Helicobacter pylori in gastric aspirates by polymerase chain reaction.

The detection of Helicobacter pylori in gastric aspirate was examined by using the polymerase chain reaction (PCR) method for amplifying a specific fragment of the urease gene A. The ability of PCR to amplify H. pylori-specific DNA was analyzed by Southern hybridization with an internal oligonucleotide probe. Twenty-two H. pylori strains from clinical isolates and reference strains were studied, and all H. pylori strains yielded a 356-bp product that hybridized with the oligonucleotide probe, whereas no amplification was evident with 18 non-H. pylori strains. This could detect as little as 50 CFU of H. pylori in pure culture and 0.1 pg of purified chromosomal DNA. A total of 50 dyspeptic patients were examined for the presence of H. pylori by culture, the rapid urease test and histological examination of antral biopsy samples as well as by PCR in gastric juice aspirate samples. The gold standard for the presence of H. pylori was established by minimum concordance of two of three tests performed on biopsy specimens. With this gold standard, 34 of the 50 patients were considered to harbor H. pylori infection. PCR correctly identified 32 (94.1%) of these 34 infected patients. PCR had the best combination of sensitivity and specificity in assessing the correct diagnosis of H. pylori as compared with those of the rapid urease test and culture. Moreover, we established a fast and simple method for use by improvement of DNA extraction. PCR of the gastric aspirate was shown to be a sensitive and specific procedure which may be an attractive alternative to methods currently used for diagnosis of H. pylori infection.