[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Other Gram-negative rods](https://durgical.com/en/microbiology/groups/other-gram-negative-rods/) › Helicobacter pylori [Microbiology](https://durgical.com/en/microbiology/) · [Other Gram-negative rods](https://durgical.com/en/microbiology/groups/other-gram-negative-rods/) # Helicobacter pylori - Bacterium - Gram-negative - Exam priority: high A bacterium that lives in the stomach, usually from childhood. It causes gastritis and ulcers and raises the risk of stomach cancer. Updated 2026-11-01 ## Key points - Urease-positive: the basis of the breath test and the rapid biopsy test. - Main cause of duodenal ulcer and a risk factor for gastric adenocarcinoma and MALT lymphoma. - Stool antigen or breath test for active infection; serology is useless for follow-up. - Treatment: proton pump inhibitor plus antibiotics; clarithromycin resistance sets the regimen. - Microaerophilic, curved and flagellated, like Campylobacter. ## At a glance **Gram** Gram-negative **Shape** Curved or spiral rod with flagella **Oxygen** Microaerophilic **Family** Helicobacteraceae **Stain** Gram: curved red rods; in biopsies, Giemsa or silver ## Morphology - Curved Gram-negative rod with several flagella at one end - Urease-, catalase- and oxidase-positive - Lives under the mucus layer of the gastric antrum ## Transmission - Person to person by oral-oral or fecal-oral routes, mostly in childhood and within families - Contaminated water and food are possible sources **Reservoir:** Human stomach ### Isolation precautions What the care team adds to standard precautions. - Standard ## Virulence factors - Urease: makes ammonia that neutralizes the acid around it and injures the mucosa - Flagella: swim through gastric mucus - Adhesins: attach to the epithelium - CagA and VacA: strong inflammation, cell damage and higher ulcer and cancer risk ## Diseases it causes - Chronic gastritis, mainly of the antrum [Helicobacter pylori gastritis →](https://durgical.com/en/conditions/helicobacter-pylori-gastritis/) - Duodenal and gastric peptic ulcer [Peptic ulcer disease →](https://durgical.com/en/conditions/peptic-ulcer-disease/) - Gastric adenocarcinoma (group 1 carcinogen) [Gastric cancer →](https://durgical.com/en/conditions/gastric-cancer/) - Gastric MALT lymphoma, which can regress after eradication ## Clinical picture - Most infected people have no symptoms - Burning epigastric pain, often on an empty stomach - Alarm signs: GI bleeding, weight loss, anemia, persistent vomiting ## Diagnosis - Urea breath test and stool antigen: detect active infection - Endoscopy with biopsy: rapid urease test, histology and culture - Serology cannot tell current from past infection - Recent proton pump inhibitors, bismuth or antibiotics can give false negatives - Eradication is confirmed after treatment ## Treatment A proton pump inhibitor combined with antibiotics: bismuth quadruple therapy (bismuth, metronidazole and tetracycline) where clarithromycin resistance is high, or amoxicillin-clarithromycin therapy where it is low. Resistance to clarithromycin and metronidazole is the main reason treatment fails. Drug class only; doses and regimens are set by the clinician from the current guideline. In Pharmacology: - [Proton pump inhibitors (PPIs)](https://durgical.com/en/pharmacology/classes/proton-pump-inhibitors/) - [Omeprazole](https://durgical.com/en/pharmacology/omeprazole/) - [Amoxicillin](https://durgical.com/en/pharmacology/amoxicillin/) - [Clarithromycin](https://durgical.com/en/pharmacology/clarithromycin/) - [Metronidazole](https://durgical.com/en/pharmacology/metronidazole/) - [Bismuth subsalicylate](https://durgical.com/en/pharmacology/bismuth-subsalicylate/) - [Tetracycline](https://durgical.com/en/pharmacology/tetracycline/) ## Prevention - Safe water, handwashing and well-prepared food - No vaccine - Testing and eradication are considered in families with gastric cancer ## In Colombia H. pylori infection is very common in Colombia and is usually acquired in childhood; gastric cancer is one of the leading causes of cancer death in the country, with the heaviest burden in the Andean regions. ## Memory aid "H. pylori packs its own antacid": urease makes ammonia and builds a small alkaline shelter inside the stomach. ## Test yourself Think of the answer, then tap the question to see it. ## Which enzyme lets H. pylori survive in the stomach, and which test uses it? Urease, which makes ammonia; it is used in the urea breath test and the rapid urease test on biopsies. ## Which cancers are linked to H. pylori infection? Gastric adenocarcinoma and gastric MALT lymphoma. ## Why is serology useless to confirm eradication? Antibodies persist long after the bacterium is gone. ## What does bismuth quadruple therapy contain? A proton pump inhibitor, bismuth, metronidazole and tetracycline. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/helicobacter-pylori/) ## Related - [Campylobacter jejuni](https://durgical.com/en/microbiology/campylobacter-jejuni/) ## Related conditions - [Helicobacter pylori gastritis](https://durgical.com/en/conditions/helicobacter-pylori-gastritis/) - [Peptic ulcer disease](https://durgical.com/en/conditions/peptic-ulcer-disease/) - [Gastric cancer](https://durgical.com/en/conditions/gastric-cancer/) ## What the colours mean **Gram-positive** Thick peptidoglycan wall: stains purple. **Gram-negative** Thin wall with an outer membrane: stains pink. **Acid-fast** Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain. [← Back to the group: Other Gram-negative rods](https://durgical.com/en/microbiology/groups/other-gram-negative-rods/) Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [Helicobacter pylori Infection](https://www.msdmanuals.com/professional/gastrointestinal-disorders/gastritis-and-peptic-ulcer-disease/helicobacter-pylori-infection) (MSD Manual Professional Edition, 2025); [Helicobacter pylori Infections](https://medlineplus.gov/helicobacterpyloriinfections.html) (MedlinePlus, 2025). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/microbiology/helicobacter-pylori/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/helicobacter-pylori/