H. pylori
Formal Definition
Helicobacter pylori; a gram-negative, spiral-shaped bacterium that colonizes the gastric mucosa, causing chronic gastritis, peptic ulcer disease (responsible for ~70% of gastric and ~90% of duodenal ulcers), and significantly increasing the risk of gastric adenocarcinoma and MALT lymphoma; treated with triple or quadruple antibiotic regimens.
How It's Used on the Ward
"H. pylori positive" or "test and treat for H. pylori" — the bug behind most ulcers, found with a urea breath test or stool antigen test.
Example
""45-year-old with epigastric pain and positive urea breath test: classic H. pylori peptic ulcer disease. Starting triple therapy — clarithromycin, amoxicillin, and PPI twice daily for 14 days. Retest for eradication in 4 weeks.""
Clinical Context
Testing: urea breath test or stool antigen test (non-invasive, preferred); biopsy-based CLO test (endoscopy). Stop PPIs 2 weeks before urea breath test (false negatives). Eradication therapy: first-line is clarithromycin-based triple therapy (PPI + clarithromycin + amoxicillin) for 14 days in areas with low clarithromycin resistance; bismuth quadruple therapy preferred in high-resistance areas. Confirm eradication 4 weeks after completing antibiotics. H. pylori is a WHO Group I carcinogen — eradication reduces gastric cancer risk. Serology (IgG) cannot distinguish active from past infection — do not use for test-of-cure.