Quantitative study of Helicobacter pylori in gastric mucus by competitive PCR using synthetic DNA fragments.

Helicobacter pylori is closely related to upper gastrointestinal diseases, and the precise evaluation of H. pylori infection is necessary for the treatment of these diseases. The aim of the present study was to establish a method for the quantitative detection of H. pylori. We applied a competitive PCR method using various amounts of synthetic DNA fragments containing the same primer-binding and a subset of the same template sequences as the target competing for primer binding and amplification in order to quantify H. pylori in gastric mucus. The results obtained by this method were compared with the results of histological examination, the rapid urease test, bacterial culture, the [13C]urea breath test, and urea and ammonia measurements in gastric juice. As the quantity of H. pylori in gastric mucus increased, the rates of positivity of histological examination, the rapid urease test, and bacterial culture increased. The quantity of H. pylori in gastric mucus was also significantly correlated with the results of the [13C]urea breath test and was negatively correlated with the urea/ammonia ratio in gastric juice. The competitive PCR method provides an objective measure of the quantity of H. pylori and makes it possible to distinguish true negatives from false negatives due to incomplete PCR and true positives from false positives due to contamination. This method is very useful for the precise evaluation of gastric H. pylori infection.