Diagnosis of Helicobacter pylori infection

Overview of Helicobacter pylori infection

Helicobacter pylori bacterium (formerly known as Campylobacter pylori or pyloridis) is a gram-negative bacterium that is usually found in the stomach and duodenum and is associated with gastritis and peptic ulcers. H. pylori attach to the mucous cells of the stomach and cause the inflammation of the stomach lining. H. pylori infection spreads via oral-to-oral, fecal-to-oral contact, contaminated food or water.

Both noninvasive and invasive tests are performed to detect H.pylori infection and diagnose the associated gastric disorders. Noninvasive tests are preferred unless there are specific indications for invasive testing (e.g., malignancy or peptic ulcer is suspected).

Blood sample taken for serology testingIndications for testing for Helicobacter pylori infection

  • Presence or history of the duodenal or gastric ulcer;
  • In order to evaluate the effectiveness of eradication therapy;
  • Persons with gastric low-grade MALT lymphoma;
  • Individuals with atrophic gastritis;
  • After endoscopic resection of early gastric cancer;
  • Individuals with dyspepsia;
  • For those who undergo chronic NSAID/aspirin therapy;
  • For those who undergo chronic antisecretory drug therapy (e.g., due to gastroesophageal reflux disease);
  • Those who have relatives who suffer from gastric cancer patients;
  • Those who have relatives who suffer from a duodenal ulcer;
  • Those who have relatives who have H. pylori infection;

Noninvasive tests

To detect the presence of H. pylori several noninvasive tests may be performed:

  • Stool antigen test: H. pylori fecal antigen test;
  • Carbon 13or carbon 14 urea breath test – a person is drinking urea (usually with a beverage) labeled with a carbon isotope (nonradioactive isotope 13C or a minor dose of radioactive 14C). Urease produced by H.pylori hydrolyzes urea. Afterward, the concentration of the carbon is measured in breath samples;
  • H. pylori serologic tests – Specific Immunoglobulin G against H. pylori are detected in the serum by immunoblot or enzyme-linked immunosorbent assay. Serologic tests are not used to monitor treatment effectiveness. Rapid tests are also available;

However, noninvasive tests are dependent on H.pylori load, so false-negative results are possible, especially if they are performed <4 weeks after the eradication therapy.

Invasive tests

  • Esophagogastroduodenoscopy (examination of the esophagus, stomach, and duodenum via endoscopy) with biopsy of the stomach lining and biopsy-based area test (CLO test) is performed when the malignancy or a complicated peptic ulcer are suspected.
    Esophagogastroduodenoscopy is performed to evaluate the mucous membrane of the stomach and duodenum and during this procedure, two small specimens are taken and placed into a gel containing urea and indicator. If there is H.pylori present the color of the indicator changes within minutes (sometimes up to 24 hours). Biopsy specimens are also taken from the antrum and corpus of the stomach and examined carefully to indicate the inflammation, metaplasia (reversible transformation of one cell type to another) and dysplasia (irreversible transformation of cells into the immature cells type) of the epithelial cells. H.pylori may be visualized with the help of special stains such as Gram, Giemsa or silver stains or by the means of immunofluorescence.
    It is recommended to perform an endoscopic examination after the treatment of peptic ulcer to asses the ulcer healing and exclude stomach cancer.
  • It is quite difficult to cultivate H.pylori as it is hard to isolate these bacteria. Skirrow’s medium and other nonselective mediums such as chocolate agar are used to cultivate the bacteria. H pylori have a characteristic appearance when stained and positive reactions in oxidase, urease and catalase tests confirm the presence of the bacteria. Antibioticogram may be performed to determine the bacteria’s susceptibility to antibiotics;

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