Helicobacter pylori is a corkscrew-shaped, gram-negative rod that lives in the mucous layer of the stomach. H. pylori infection is now accepted as the most common cause of gastritis, and is etiologically involved in gastric ulcer, duodenal ulcer, gastric adenocarcinoma and primary gastric B-cell lymphoma. This organism is very common, and has infected at least half of the world population. Long-term infection leads to the weakening of the stomach lining and making it more susceptible to sores and ulcers, eventually leading to other gastric problems.