Helicobacter pylori Diagnostic Kit H. pylori a Gram-negative bacterium is often found in patients with gastritis and gastric ulcers. H. pylori infection is common and begins in childhood with symptoms appearing in adulthood, however, most people don’t show symptoms. H. pylori is responsible for over half of peptic ulcers worldwide. Peptic ulcers are caused when mucous coating that protects the stomach and duodenum is damaged by both stomach acid and H. pylori. Why the bacterium causes ulcers in some people and not in others is not known. Most likely, development of ulcers depends on characteristics of the infected person; the type, or strain, of H. pylori present; and factors researchers have yet to discover. It is not clear how H. pylori is transmitted, although it is thought that it may be spread through contaminated food or water. Researchers are looking into causes of interpersonal infection. Some studies suggest that having contact with the stool or vomit of an infected person can spread H. pylori infection. H. pylori is present in saliva of some infected people, meaning infection could be spread by contact with saliva.