Q:
What time of life is associated with the highest risk of acquiring Helicobacter pylori?

A:
Early childhood.

Q:
When the prevalence of Helicobacter pylori in the developed world is graphed against the age of individuals, there seems to be a linear increase in prevalence with age. 

   100-|                  ___        
       |       ____,-----'
    80-|   ,--'      Developing world
 p     |  /
 r  60-|  |                              Note: Diagram
 e     |  |                              not accurate.
 v  40-| /             _,-'
       | |         _,-'Developed world
(%) 20-| |     _,-'
       |/  _,-'
     0- ------------------------
       0   1   2   3   4   5   6 
           0   0   0   0   0   0
                 Age (years)

Explain the epidemiology behind this.

A:
This linear increase is thought to be due to a cohort phenomenon. It is thought that the prevalence of Helicobacter pylori in the environment has been gradually decreasing over time and hence with each generation of children fewer were infected by Helicobacter pylori.

Q:
What factors are associated with the acquisition of H. pylori?

A:
Childhood living conditions:
  - Poor socioeconomic status
  - Sharing a bed in childhood
  - High density living

Q:
What are the modes of transmission?

A:
Medical science is still unsure about the modes of transmission. 
Possible modes:
  * Faecal - Oral
  * Oral - Oral
  * Gastro - Oral
These are all controversial.

Q:
True or false? Sheep and cattle are animal reservoirs for H. pylori.

A:
False. Transmission is human to human. There is no evidence for an alternative source of infection.

Q:
What is the most common presentation of H. pylori infection?

A:
Chronic gastritis with activity (PMN infiltration).

Q:
What diseases does H. pylori infection cause?

A:
* Gastritis
* Peptic ulcer diease
   - Duodenal ulcer
   - Gastric ulcer
* Gastric Cancer
* B cell MALT lymphoma

Q:
True or false? Even after treating peptic ulcer disease and eradicating H. pylori there is an 80% chance of relapse within 1 year.

A:
False. *Before* the discovery of H. pylori there was an 80% chance of relapse within 1 year. Now, after treatment, relapse is close to 0%.

Q:
What is the Correa hypothesis for the aetiology of gastric cancer?

A:
An unknown environmental factor
(possibly high salt diet, low vitamin C or a carcinogen)
   ->
Gastritis
   ->
Atrophy
   ->
Intestinal metaplasia
   ->
Dysplasia
   ->
Adenocarcinoma

Q:
What are the proposed reasons for why only a small proportion of people infected with H. pylori develop disease?

A:
* Bacterial virulence factors (are different between strains)
     -No conclusive evidence (cagA and VacA only appear virulent in developed world)
* Host factors
* Environmental factors

Q:
What differences in the development of disease are associated with the age of infection?

A:
Childhood infection predisposes to: 
  - Gastric ulcer
  - Gastric cancer
  - Inhibits duodenal ulcer

Later infection predisposes to:
  - Duodenal ulcer

Q:
Why are most organisms unable to survive in high acid environments such as the stomach?

A:
The high H+ concentraion counteracts the proton motor force which provides energy for the cell in most bacteria.

Q:
Why is H. pylori able to survive in the high acid environment of the stomach when most organisms cannot?

A:
The urease enzyme allows H. pylori to survive at low pH. Urease neutralises the gastric acid by production of ammonia which binds with portons forming ammonium ions.

Q:
What anatomical portion of the stomach secretes acid?

A:
The body. 
Note: Not the antrum.

Q:
What is thought to be the optimal pH range for H. pylori to grow in?

A:
5.0 - 6.0

Q:
True or false? In H. pylori infected stomaches with high acid H. pylori grows in the body of the stomach.

A:
False. In H. pylori infected stomaches with high acid H. pylori grows in the *antrum* of the stomach. Predisposing the individual to a duodenal ulcer.

Q:
True or false? In H. pylori infected stomaches with low acid H. pylori grows in the body of the stomach.


A:
True.

Q:
What kind of peptic ulcer disease does a H. pylori infection in a stomach with low acid levels predispose an individual to?

A:
Gastric ulcer.

Q:
What factors influence the acid levels in the stomach?

A:
* Diet
* Genetic background
* Acid suppressive therapy

Q:
What dietary factors increase the risk of gastric cancer?

A:
* High salt intake
* High intake of spicy foods
* Low intake of fresk vegetables

Q:
What is the C13-urea breath test?

A:
Patients ingest urea containing the C13 isotope. If H. pylori is present it will break down the urea with its urease enzyme. The patient's breath is then tested for CO2 containing C13.

Q:
Why is serology not a good method to check if a patient has responded to antibiotic treatment to eradicate H. pylori?

A:
Antibodies take up to a year to fall after an organism is removed.

Q:
What 3 tests can be done to detect H. pylori using a gastric biopsy?

A:
* Culture (not done in most cases)
* Biopsy usease test (white - negative, red - positive)
* Histology

Q:
What are the 3 non-invasive tests to diagnose H. pylori infection? 

A:
* Serology
* C13-urea breath test
* Faecal antigen test (detects H. pylori antigen in faeces)

Q:
What is the recommended first line therapy for H. pylori infection?

A:
Omeprazole + 
Amoxycillin +
Clarithromycin

Q:
What is the recommended first line therapy for H. pylori infection when a patient has a penicillin allergy?

A:
Omeprazole + 
Tetracycline +
Clarithromycin

Q:
True or false? A high percentage of H. pylori strains are resistant to metronidazole.

A:
False. Metrinidazole resistance is low or absent.

Q:
True or false? Given recurrence of symptoms following treatment of H. pylori, isolates of H. pylori should be obtained and sensitivity testing performed on them.

A:
True.