History and Definition of H. pylori

Helicobacter pylori (H. pylori) is a microaerophilic, spiral-shaped Gram-negative bacterium first identified in the early 1980s. Since then, its role as a major etiological factor in gastric diseases has been widely recognized [1, 2]. Early studies demonstrated that the organism can persist in highly acidic environments and is closely associated with chronic gastritis and peptic ulcer disease. These observations overturned the prevailing concept that excessive gastric acid was the sole cause of ulcer formation [1, 2]. Marshall’s self-infection experiment subsequently fulfilled Koch’s postulates and provided direct evidence of H. pylori pathogenicity [3]. In 1994, the US National Institutes of Health convened a consensus conference that confirmed the etiological role of H. pylori in peptic ulcer disease, a milestone considered a turning point that brought H. pylori research into mainstream medicine [4]. In the same year, the International Agency for Research on Cancer classified H. pylori as a Group I carcinogen [5].