H. Pylori: GI Ulceration Flashcards
What is a gram-positive cell?
Single surrounding membrane
What is a gram-negative cell?
Two membranes:
One is an inner membrane and the other is the outer membrane
What are the 5 steps of gram staining?
1) Fixation
2) Primary stain (Crystal violet)
3) Mordant (Iodine)
4) Decolourisation (Acetone)
5) Counterstaib (Safranin)
What are the characteristics of H. Pylori? (4)
Gram-negative
Helix-shaped
Requires CO2 for growth
Forms biofilms
What chemical substance does the Helicobacter produce?
Urease
Where is the H. Pylori adapted most?
Gastric mucosa
What are the symptoms of H. Pylori?
Acute gastritis Abdominal pain Nausea Flatulence Bad breath
What are the three characteristics that help H. Pylori survive?
1) Urease production
2) Motility/ flagella
3) Vacuolating cytotoxin (VacA)
How does urease help H. Pylori survive?
Urease hydrolyses urea into CO2 + NH3, therefore survival in acidic milieu.
Urea + H2O -> CO2 + NH3
What is VacA?
Increases bacterial fitness, induces apoptosis.
What are the 3 mechanisms that harm the stomach?
1) Ammonia is toxic to the cells
2) Proteases, VacA, phospholipases, cagA causes inflammation.
3) HcpA trigger an immune response.
What are the 5 tests for H. Pylori?
1) Urea breath test (UBT)
2) Serological testing- pre-treatment testing
3) Stool antigen test
4) Stool immunoassay & PCR
5) Endoscopy
What is chemotaxis?
A movement in response to a chemical stimulus.
How does H. Pylori cross the mucus layer of the stomach?
1) Swims to burrow into the mucin gel lining
2) Reaches epithelial cells underneath where neutral pH is
3) Produces urease to neutralise acid (de-gel mucin layer)
4) Adheres by adhesin production which binds to lipids and carbs on cell membrane.
How is an ulcer formed by H. Pylori?
Mucosal cell death caused by the cytotoxins and ammonia.
