Numerous diagnostic assays have been developed for the detection of Helicobacter pylori (H. pylori), including culture, the rapid urease test, the urea breath test, histology, serological and lateral flow immunoassays, stool antigen test and molecular assays targeting a variety of housekeeping genes. Although culture is considered the gold standard in the isolation of H. pylori, it is disadvantaged by the need for specific media with special growth conditions and the length of time necessary to obtain a culture result, often requiring four to five days to isolate H. pylori and a further three days to obtain susceptibilities. Contamination of gastric tissue by normal stomach flora can also cause serious interference with the culture of H. pylori. There is a clear opportunity for real-time PCR to simplify the procedure and provide more timely results. We describe a real-time Taqman probe-based assay (H. pylori qPCR) used to rapidly identify H. pylori directly from gastric biopsies.
The H. pylori qPCR was validated with 63 control strains: 30 clinical H. pylori isolates previously isolated from gastric biopsies, and 33 non-H. pylori (including six other Helicobacter species) isolates. No false-positive or false-negative results were obtained. Gastric biopsy specimens (n=75) from patients suspected of H. pylori infection were tested for clinical validation, confirmed and subtyped by pyrosequencing, and compared with culture. To date, 28 gastric biopsies were H. pylori qPCR positive and 47 specimens were H. pylori qPCR negative. All H. pylori qPCR positive results were confirmed by pyrosequencing, with no discrepant results when compared with culture.
This assay is simple to perform, easy to interpret and results are available within 2 hours. The added advantage is the ability to accurately detect H. pylori DNA in specimens where the viability of H. pylori has been compromised.