Utility of normalized genome quantification of Helicobacter pylori in gastric mucosa using an in-house real-time polymerase chain reaction

Traditional diagnostic assays for Helicobacter pylori detection have their limitations. Molecular methods can improve both diagnosis and understanding of gastric diseases. Here we describe an in-house quantitative real-time polymerase chain reaction (q-rt-PCR) for the detection of H. pylori in gastric biopsies which has been developed and has a detection limit of 10 copies, the specificity of which was tested against other gastric colonizer bacteria. In this study, 199 gastric biopsies from adults with different clinical gastric symptoms were examined. Biopsies were obtained during endoscopy and the following tests performed: rapid urease testing (RUT), culture and q-rt-PCR. H. pylori bacterial load expressed as bacterial load per 10(5) cells was calculated using a standard curve. H. pylori was isolated in 41% of patients, RUT was positive in 32% and bacterial genome was detected in 45% (p = 0.010). Concordance between traditional invasive microbiological methods used together and q-rt-PCR was almost 100%. Bacterial load in patients with positive RUT was significantly higher than those where it was negative (p<0.0001). There were also significant differences between bacterial load in patients with more than one positive assay versus those where only one method was positive (p = 0.006). The in-house q-PCR developed here is quick and inexpensive, and allows accurate diagnosis of H. pylori infection. It also permits normalized bacterial load quantification, which is important to differentiate between asymptomatic colonisation and infection.