Helicobacter pylori (H. pylori) is a Gram-negative, microaerophilic bacterium restricted to the stomach and the duodenum. It was identified in 1982 by Australian scientists Barry Marshall and Robin Warren, who found that it was present in patients with chronic gastritis and gastric ulcers, conditions that were not previously believed to have a microbial cause. H. pylori has also been associated as an etiologic agent in the development of duodenal ulcers and stomach cancer. More than fifty percent of the world’s population harbor H. pylori in their upper gastrointestinal tract. However, over 80 percent of individuals infected with this bacterium are asymptomatic and it has been postulated that it may play an important role in the natural stomach ecology.

H. pylori is a contagious bacterium, although the exact route of transmission is not known. Person-to-person transmission by either the oral-oral or fecal-oral route is most frequent. Consistent with these transmission routes, the bacteria have been isolated from feces, saliva and dental plaques of some infected patients. Transmission occurs mainly within families in developed nations, yet can also be acquired from the community in developing countries.

Signs and symptoms: Over 80% of people infected with H. pylori never experience symptoms or complications. Acute infection may appear as an acute gastritis with abdominal pain (stomach ache) or nausea. Where this develops into chronic gastritis, the symptoms, if present, are often those of non-ulcer dyspepsia: stomach pains, nausea bloating, belching and sometimes vomiting or black stool. Diagnosis: Testing for H. pylori is recommended if peptic ulcer disease is suspected, low grade gastric MALT lymphoma, after endoscopic resection of early gastric cancer, if there are first degree relatives with gastric cancer, and unfrequently, in certain cases of dyspepsia.

Laboratory diagnosis tests of H. pylori can be categorized as invasive (a biopsy check during endoscopy examined microscopically and also cultured), or noninvasive tests such as a blood antibody test, stool antigen test, or with the urea breath test (UBT) which involves the ingestion of isotopically labeled urea by the patient. None of the test methods is completely failsafe. Even biopsy is dependent on the location of the biopsy and includes risk and discomfort to the patient and colonization in patches that might be missed by biopsy. The recent Maastricht 2-2000 Consensus Report recommends the use of the stool antigen and UBT tests as an aid in the diagnosis