Gram ⊝, curved, flagellated (motile), triple ⊕: catalase ⊕, oxidase ⊕, urease ⊕- Urease produces ammonia, creating an alkaline environment, which helps H pylori survive in acidic mucosa.- Colonizes mainly antrum of the stomach

- Causes gastritis and peptic ulcers (especially duodenal)- Risk factor for peptic ulcer disease, gastric adenocarcinoma, and MALT lymphoma, B-cell lymphomas

Diagnosis: - Biopsy with culture, histology with Giemsa or silver stain. - Urea breath test: ¹³C-urea swallowed; ammonia+¹³C-CO₂ exhaled- Serology

Treatment:- Triple therapy: Amoxicillin (metronidazole if penicillin allergy) + clarithromycin + PPI for 10-14 days- Quadruple therapy where clarithromycin resistance is ≥15%, eg, PPI + bismuth + metronidazole + tetracycline