Question
Helicobacter pylori.
Answer
Helicobacter pylori is a Gram-negative, spiral/curved, microaerophilic bacterium that colonizes the gastric mucosa (mainly the antrum), and is the major recognized cause of chronic gastritis, peptic ulcer disease, and a Group I (definite) carcinogen for gastric adenocarcinoma and gastric MALT lymphoma.
Key virulence features: multiple polar flagella provide motility to burrow through the protective gastric mucus layer; produces abundant urease, hydrolysing urea to ammonia and CO2, locally neutralizing gastric acid and creating a favourable microenvironment (also exploited diagnostically); the CagA and VacA virulence factors (in more pathogenic strains) directly damage epithelial cells and provoke chronic inflammation, contributing to ulceration and the stepwise progression toward malignancy.
Laboratory diagnosis:
- Invasive: rapid urease test (CLO test) on biopsy; histopathology (Giemsa stain showing curved organisms); culture (technically demanding but allows susceptibility testing).
- Non-invasive: urea breath test (isotope-labelled urea, detects labelled CO2 in exhaled breath — also used to confirm eradication); stool antigen test; serology (detects past or current exposure, not useful to confirm cure).
Treatment: triple/quadruple therapy combining a proton-pump inhibitor with two antibiotics (commonly amoxicillin, clarithromycin, or metronidazole, ± bismuth), for 10–14 days, to eradicate the organism and allow ulcer healing.