C3 The Biology Of Dyspepsia 3: H.pylori Flashcards
Does gastric ulceration bacteria of H. Pylori have short term survival and able to colonise?
Long term effect and able to colonise
Do bacteria associated with nausea, vomiting and diarrhoea have short term survival and able to colonise?
Have short term survival and unable to colonise
Why are asymptomatic infections not well understood?
Individual characteristics (immune system)
Characteristic of specific strain of H.pylori
Other unknown factors
What are the requirements for H.pylori colonisation in the stomach?
Acid neutralising system- urease enzyme, transporter proteins
Adhesion molecules - present on outer membrane; bind sugar molecules on surface of stomach
Movement- flagella
Degradation of mucus - enzymes: lipase protease
What are the consequences of H.pylori colonisation of the stomach?
Mucus later damaged, epithelial cells no longer protected against gastric acid
What are the key components of the acid neutralising activity of H.pylori?
Urease enzyme (10% of total protein) Proton gated urea transporter
What is the urease enzyme comprised of?
Two amino acid chains alpha and beta
Functional urease enzyme
Contains 4 (a&b)3 modules
24 amino acid chains
Co factor: two Ni2+ ions per beta chain
What is the proton gated urea channel comprised of?
Single amino acid chain
Functional channel:homohexamer
Ring like structure
What pH is the proton gated urea Channel opened and closed at?
pH< 5 channel fully open
pH > 7 channel closed
What do non invasive H.pylori diagnostic checks include?
Breath
Blood
Stool
What are invasive diagnostic checks for H.pylori?
Gastroscopy, biopsy for culture (CLO test)
What are the advantages of invasive test?
Sensitivity testing:
- patients with reduced antibiotic choice
- patients who received eradication therapy, but remain helicobacter positive
What is the urea breath test?
Detection based on urease enzyme activity , detection of heavy isotopes carbon 13 non radioactive
What are the 4 main parts of the quick strip test?
Reaction zone
Test zone
Control zone
Absorbent pad
What are monoclonal antibodies?
Single antibody produced by cells
What are polyclonal antibodies?
Mixture of antibodies isolated from serum
What are the 4 steps of H.pylori blood test?
1) add patient sample
2) only antibody recognising H.pylori binds; other antibodies are washed away
3) enzyme linked antibody recognising human antibody
4) colour reaction optical density measured
Why is a combination of two antibiotics used in eradication therapy?
H.pylori displays poor sensitivity to any single antibiotic, combo of two can be much more potent than one
