Question
A biopsy was taken from a patient, clinically diagnosed with acid peptic disease, during endoscopy.
- (a) Name the site from where the biopsy most likely was taken. 1 mark(s)
- (b) Name the etiological agent and list two mechanisms by which the agent can produce this condition. 3 mark(s)
- (c) Describe a rapid test done on the biopsy material for the above etiological agent. 2 mark(s)
Answer
(a) Site of biopsy: the gastric antrum (the most common and most sensitive biopsy site for detecting the organism, though biopsies from the body of the stomach are also taken in some protocols).
(b) Etiological agent and mechanisms: Helicobacter pylori — a curved/spiral, microaerophilic, Gram-negative bacillus. Mechanisms by which it produces acid-peptic disease:
- Urease production: the organism produces large amounts of urease, hydrolyzing host urea into ammonia and carbon dioxide; the ammonia neutralizes gastric acid locally, creating a protected microenvironment, but ammonia and other metabolic products also directly damage the gastric epithelium, contributing to mucosal injury.
- Virulence factor-mediated epithelial damage: the cag pathogenicity island (encoding a type IV secretion system injecting the CagA protein into host epithelial cells, disrupting normal cell signalling) and the VacA vacuolating cytotoxin (causing epithelial cell vacuolation and damage) mark more aggressive strains, driving chronic mucosal inflammation, epithelial damage, and, over time, peptic ulceration; the organism’s spiral shape and polar flagella also allow it to burrow through the protective gastric mucus layer to reach and persistently colonize the epithelial surface beneath, sustaining chronic inflammation.
(c) Rapid test on biopsy material: the Rapid Urease Test (CLO test) — the gastric biopsy specimen is placed in a urea-containing medium with a pH indicator; if H. pylori is present, its urease splits the urea, raising the pH and producing a visible colour change (typically within hours) — a fast, cheap test, and the most commonly used method when endoscopy is already being performed.