Helicobacter pylori is a spiral shaped bacterium that lives in the stomach
and duodenum (section of intestine just below stomach). It has a unique
way of adapting in the harsh environment of the stomach.
The inside of the stomach is bathed in about half a gallon of gastric
juice every day. Gastric juice is composed of digestive enzymes and concentrated
hydrochloric acid, which can readily tear apart the toughest food or microorganism.
Bacteria, viruses, and yesterdays steak dinner are all consumed in this
deadly bath of chemicals. It used to be thought that the stomach contained
no bacteria and was actually sterile, but Helicobacter pylori changed
The stomach is protected from its own gastric juice by a thick layer
of mucus that covers the stomach lining. Helicobacter pylori takes advantage
of this protection by living in the mucus lining.
|Urea hydrolysis: urea is broken down
to ammonia and carbon dioxide
Once H. pylori is safely ensconced 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
reaction of urea hydrolysis is important for diagnosis of H.pylori by
the breath test.
|Gram stain of H. Pylori
Another defense H. pylori has is that the body's natural defenses cannot
reach the bacterium in the mucus 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 go away either, though,
and the immune response grows and grows. Polymorphs 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 inflammation of the stomach lining; i.e. the response to H. pylori.
|H. Pylori causing a neutrophil reaction
(active chronic gastritis) in the lining (mucosa) of the stomach
H. pylori is believed to be transmitted orally. Many researchers think
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-esophagal reflux (in which a small amount of the stomach's contents
is involuntarily forced up the esophagus) or belching, common symptoms
of gastritis. The bacterium could then be transmitted through oral contact.