Helicobacter pylori was first cultured in April 1982 by pathologist J. Robin Warren and clinical fellow Barry J. Marshall at Royal Perth Hospital, Australia. Their work overturned the long-held view that the stomach was sterile and that peptic ulcer disease was caused by acid, stress, and diet.^[1][2] The findings were published in The Lancet in 1983 and 1984. Causation was then supported by Marshall’s 1984 self-ingestion experiment and by 1990 trials showing that eradication cures duodenal ulcer. Two watershed events followed in 1994: the NIH recommended antibiotic therapy for infected ulcer patients, and the International Agency for Research on Cancer (IARC) classified H. pylori as a group 1 human carcinogen. Warren and Marshall received the Nobel Prize in Physiology or Medicine in 2005. Since then, rising antibiotic resistance has moved first-line therapy away from clarithromycin-based triple therapy. Current options are 14-day bismuth quadruple therapy and regimens built on vonoprazan, a potassium-competitive acid blocker.^[3]

• Before 1982: Spiral organisms in the stomach had been described intermittently for over a century. However, the dogma of a sterile stomach and an acid/stress model of ulcer disease discouraged investigation of a microbial cause.^[4][5]
• 1982 – Discovery and first culture: Warren repeatedly observed small curved bacilli on the gastric surface epithelium adjacent to active chronic gastritis. Marshall first cultured the organism over the Easter weekend of April 1982, after incubation plates were inadvertently left beyond the routine 48 hours.^[1][5]
• 1983–1984 – Publication: The initial observations appeared as letters in The Lancet in 1983.^[6] A 1984 study of 100 consecutive patients undergoing gastroscopy followed. Curved bacilli were present in almost all patients with active chronic gastritis, duodenal ulcer, or gastric ulcer, and the authors proposed an etiologic role.^[7] The organism was first named Campylobacter pyloridis (later C. pylori), and the causal hypothesis initially met widespread skepticism.^[1]
• 1984 – Self-experimentation: No animal model was available to fulfill Koch’s postulates. Marshall therefore ingested a culture of the organism, developed acute gastritis, and documented the histologic changes.^[8]
• 1989 – Reclassification: Ultrastructural, biochemical, and genetic differences from Campylobacter led to transfer of the organism to a new genus, as Helicobacter pylori.^[9]
• 1990 – Eradication cures ulcer disease: Clinical trials showed that eradication heals duodenal ulcers and markedly reduces recurrence. This completed the causal argument and reframed peptic ulcer disease as a curable infection rather than a chronic condition requiring lifelong acid suppression.^[10][4]

• 1994 – NIH Consensus Conference: The panel concluded that H. pylori is strongly associated with ulcer disease. It recommended antimicrobial therapy for ulcer patients with H. pylori infection.^[11]
• 1994 – IARC classification: The IARC/WHO working group classified H. pylori infection as a group 1 (definite) human carcinogen for gastric adenocarcinoma. It was the first bacterium to receive this designation.^[12][1]
• Mid-to-late 1990s – Regulatory approval and international consensus: The U.S. Food and Drug Administration approved the first dedicated eradication regimens.^[13] In parallel, the European Maastricht consensus series (Maastricht I, 1996) began standardizing indications, diagnosis, and treatment internationally.^[4] These first-generation regimens, built on clarithromycin, ranitidine bismuth citrate, or H2-receptor antagonists, are now obsolete.^[3]
• 2001 – Prospective confirmation of the gastric cancer link: In a Japanese prospective cohort, gastric cancer developed in H. pylori-infected but not uninfected patients over a mean follow-up of 7.8 years. This supported eradication as a cancer-prevention strategy.^[14]
• 2005 – Nobel Prize: Barry J. Marshall and J. Robin Warren were jointly awarded the Nobel Prize in Physiology or Medicine “for their discovery of the bacterium Helicobacter pylori and its role in gastritis and peptic ulcer disease.”^[15]

• Resistance era: Rising clarithromycin and levofloxacin resistance progressively eroded the efficacy of legacy proton pump inhibitor–clarithromycin triple therapy. Recommendations shifted toward bismuth quadruple therapy and susceptibility-guided approaches.^[3][16]
• 2022 – ICD-11 and Maastricht VI/Florence: H. pylori gastritis is now classified as an infectious disease in ICD-11. The Maastricht VI/Florence consensus endorsed the principle that all infected individuals should be offered treatment.^[16]
• 2022 – Potassium-competitive acid blockers: The FDA approved vonoprazan-based dual therapy (vonoprazan–amoxicillin) and triple therapy (vonoprazan–amoxicillin–clarithromycin). Approval followed a U.S./European phase 3 trial in which both regimens were noninferior to lansoprazole-based triple therapy, and superior overall and in clarithromycin-resistant strains.^[17]
• 2024 – ACG Clinical Guideline: The guideline substantially revised the 2017 recommendations:^[3]
  • Bismuth quadruple therapy for 14 days is the preferred regimen for treatment-naive patients when antibiotic susceptibility is unknown. This is a strong recommendation based on moderate-quality evidence.
  • Empiric clarithromycin-based regimens are no longer recommended.
  • Rifabutin triple therapy and vonoprazan–amoxicillin dual therapy are alternatives.
  • Universal post-treatment test-of-cure is advised.