Helicobacter pylori is a gram-negativebacterium that lives inside the mucus lining of the stomach. It belongs among the proteobacteria. Many gastric ulcers are caused by H. pylori infection, although most humans are infected and not all infections lead to symptoms. Two strains of H. pylori have been sequenced.
... out with 29.5% under the age of 18, 6.7% from 18 to 24, 33.6% from 25 to 44, 20.6% from 45 to 64, and 9.6% who are 65 years of age or older. The median age is 35 years. ...