In recent years, Helicobacter pylori (H. pylori) has been identified by researchers as the cause of the majority of gastrointestinal ulcers. H. pylori is a bacterium that lives in the stomach and duodenum. It has a unique way of adapting to the usually harsh environment of the stomach.
Incidence; Causes and DevelopmentH. pylori
is very common, infecting more than a billion people worldwide. It is estimated that half of the United States population older than age 60 has been infected with H. pylori
. Infection usually persists for many years, leading to ulcer
disease in 10 % to 15% of those infected. H. pylori
is found in more than 80% of patients with gastric and duodenal ulcers
Gastric juice is composed of digestive enzymes and concentrated hydrochloric acid
, which can readily digest food or kill microorganisms. Low levels of stomach acid increase the chance an organism's survival. It used to be thought that the stomach contained no bacteria
and was actually sterile.
The stomach is protected from its own gastric juice by a thick layer of mucus that covers the stomach lining. H. pylori
takes advantage of this protection by living in the mucous lining.
Once H. pylori is safe in the mucus, it is able to fight the stomach acid that does reach it with an enzyme it possesses called urease. Urease converts urea, of which there is an abundant supply in the stomach (from saliva
and gastric juices), into bicarbonate and ammonia, which are strong bases. This creates a cloud of acid-neutralizing chemicals around the H. pylori
, protecting it from the acid in the stomach. The breath test method of diagnosis relies on this reaction being present.
Contributing to the protection of H. pylori
is the fact that the body's natural defenses cannot reach the bacterium
in the mucous lining of the stomach. The immune system will respond to an H. pylori
infection by sending white cells, killer T-cells
, and other infection-fighting agents. However, these potential H. pylori
eradicators cannot reach the infection, because they cannot easily get through stomach lining. They do not, however, go away – the immune response just grows and grows. White cells die and spill their destructive compounds (superoxide radicals) on stomach lining cells. Extra nutrients are sent to reinforce the white cells, and the H. pylori
can feed on this. Within a few days, gastritis
and perhaps eventually a peptic ulcer
results. It may not be H. pylori
itself which causes peptic ulcer
, but the body's response (inflammation
of the stomach lining).H. pylori
is believed to be transmitted orally. Many researchers believe that H. pylori
is transmitted orally by means of fecal matter through the ingestion of waste-tainted food or water. In addition, it is possible that H. pylori
could be transmitted from the stomach to the mouth through gastro-esophageal reflux or belching, common symptoms of gastritis. The bacterium could then be transmitted through oral contact.
Treatment and Prevention
A 2002 trial demonstrated that a mixed probiotic acidophilus
preparation failed to eradicate the H. pylori
infection in the patients upon whom it was tried. [Digestion 2002;65(1): pp.16-20