Exercise 4: Molecular Typing Methods - H. pylori

Question 1

What are the morphological features of Helicobacter pylori?

Answer 1

• Gram negative
• Helical/spiral shaped
• Microaerophilic (2-6% O2)
• Has polar flagella
• Motile
• Fastidious

Question 2

What are the incubation conditions for H. pylori?

Answer 2

• HBA at 37 degrees (any media supplemented with blood)

- 2-6% O2 environment

Question 3

What are H. pylori’s virulence factors?

Answer 3

• Adhesion molecules: BabA, SabA
• Urease (Catalyses the hydrolysis of urea into carbonic acid and ammonia; the ammonia produced neutralises stomach acid and damages the mucosal surface)
• Flagella (enables H. pylori to burrow into the mucous lining of the stomach)
• Chemotaxis (H. pylori chemotaxes to urea, bicarbonate, mucin and amino acids)
• Outermembrane vesicles (resemble the bacterial outer membrane; transport peptidoglycan and vacA into host cells)
• VacA (multifunctional toxin)
• Peptidoglycan (delivered via both T4SS and OMV; causes an inflammatory response through the activation of IL-8)
• cagA - (delivered via T4SS; causes cytoskeletal changes)

Question 4

How is H. pylori infection treated/prevented?

Answer 4

• Combination of 2-3 antibiotics alongside a PPI

Question 5

What are the clinical outcomes of H. pylori infection?

Answer 5

• > 80% - Gastritis
• 15-20% - Duodenal or Gastric ulcers, intestinal metaplasia
• <1% - Gastric cancer

Question 6

Describe how the information arising from the genotyping of H. pylori may be useful to the clinician

Answer 6

• The clinician will be able to determine if it is a pathogenic strain or not (ie if the has a cagPAI)
• This may aid in developing a treatment plan

Question 7

Besides microscopic and molecular testing, what other clinical tests may provide rapid detection and identification of H. pylori?

Answer 7

Nonendoscopic

• Urea breath test
• Faecal antigen test

Endoscopic
- Urease based test (CLOtest)