Helicobacter pylori (H. pylori) is a gram-negative spirochete bacterium that is commonly found in the stomach.

• Commonest in population (10-80%) based on hygiene
• Positive in ~100% of Chronic gastritis & PUD patients.
• Duodenal ulcer precedes gastric metaplasia

Demographics

• Affects up to 50% of the population worldwide, with a higher prevalence in developing countries.
• In developed countries, infection with H. pylori is unusual in childhood but becomes more common during adulthood. However, in developing countries, most children are affected with H. pylori before age 10.

Risk Factors

• Low SES, elderly, migrants, institutionalised individuals.
• Poor hygiene practices.
• The likelihood of infection is most strongly related to living conditions in childhood (when acquisition usually occur but remains asymptomatic).
• Infection is more frequent in family members of an infected person or in people with a family Hx of PUD or gastric cancer.
• Transmission of H. pylori most commonly occurs via the faecal-oral and oral-oral routes.

Pathogenesis

• Gram negative, Spirochete, Does not invade tissue.
  • Colonize mucous layer of Acidic Gastric mucosa only