GI Infections - Helicobacter Pylori Flashcards Preview

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Flashcards in GI Infections - Helicobacter Pylori Deck (13)
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1
Q

Describe the features of Helicobacter pylori

A

Spiral Gram negative rod but polymorphic
- in adverse conditions (it becomes coccoidal in shape)

It has one to five unipolar flagella, each with a membranous terminal bulb, is highly motile

Causes chronic diseases of the GI tract

2
Q

Describe the epidemiology of Helicobacter pylori

A

H.pylori is uncommon in young children

In developing countries:-
- Most adults are infected
- Most children are infected by their teens
Acquisition occurs in about 10% of children per annum between the ages of 2 and 8 years so that most are infected by their teens
15 – 20% of infected develop severe GI disease

In developed countries:-
H.pylori affects about 20% of persons below the age of 40 years, and 50% of those above the age of 60 years. Low socio-economic status predicts H.pylori infection
Immigration is responsible for isolated areas of high prevalence in some Western countries

3
Q

How is H. Pylori transmitted?

A

Route is still not confirmed

Appears to be only one reservoir - human stomach

  • person to person most likely route of infection
  • faecal-oral route - cultured in faeces
  • oral-oral route - found in dental plaque using PCR
4
Q

What are the virulence factors of H. pylori?

A

1) Urease converts urea (from saliva and gastric juices), into bicarbonate & ammonia, which are alkaline
- creates cloud of acid neutralising chemicals around H. pylori, protecting it from the acid in stomach
2) Motility - uses spiral shape and flagella
3) Vacuolating cytotoxin - produce acidified vacuoles leading to cell death - cell eventually dies - pool of nutrients
4) Adhesion pedestal - adhere to host cell
5) Resistance to Immune response - suppresses immune response and also partially resists killing by phagocytes
6) Phospholipase – mucus breakdown
7) Cag Pathogenicity Island:
- Type IV secretion system (made up of ~ 11 proteins evolved from conjugation apparatus)
- Cag A (cytotoxin-associated gene A) – increases acid production and alters cell division/apoptosis balance

5
Q

How does H. pylori infection present?

A

Because of strain and host variation H.pylori has various disease clinical presentations:
Gastritis
Non-ulcer dyspepsia
Stomach cancer
Duodenal & Gastric Ulcers
Non gastric diseases - coronary heart disease, skin rashes, chronic halitosis, sudden infant death syndrome

6
Q

Describe gastritis caused by H. pylori

A

All Hp infected patients develop chronic gastric inflammation (type B) but condition is usually asymptomatic

H.pylori colonises and infects the gastric mucosa

  • chronic gastric inflammation (type B) –normally asymptomatic
  • gastric mucosa infiltrated by mononuclear & polymorphonuclear leukocytes (WBC)

Intestinal metaplasia – gastric mucosa resembles intestine mucosa (atrophy)

7
Q

Describe non-ulcer dyspepsia associated with H. Pylori

A

25 % of population suffer
H. pylori present in 30-60% of patients

Recurrent abdominal pain or discomfort centred in upper abdomen, some may suffer nausea or chronic vomiting

Role of H. pylori in non-ulcer dyspepsia remains unclear, but many doctors treat with antibiotics if H. pylori present

8
Q

Describe the features of stomach cancer associated with H. pylori

A

Stomach cancer causes 750,000 deaths per year; 70-90% cases due to H.pylori infection
Most common in countries such as Colombia and China, where H. pylori infects over half the population in early childhood.
Classified as a type I carcinogen by the WHO

Long term tissue damage favours cell proliferation gives increase risk of malignant alterations
Intestinal atrophy occurs - precursor lesion to cancer

Other risk factors include low Vits C & E, calcium, high salt & smoking

9
Q

Describe the features of duodenal and stomach ulcers associated with H. pylori

A

Present in 70-100 % of patients

Gastritis is known to be the essential pre-requisite for peptic ulceration

10
Q

Describe the pathogenesis of duodenal and stomach ulcers associated with H. pylori

A

“Ulcer strain” produces vacuolating cytotoxin

Induces inflammation (neutrophils), apoptosis, atrophy

Breakdown in mucosal defences - acid attack of gastric or duodenal mucosa

11
Q

What are the symptoms of duodenal and stomach ulcers associated with H. pylori?

A

Burning pain in the epigastrium - when the stomach is empty, relieved by eating or by taking antacids.

Less common symptoms include: 
Nausea
Vomiting
Loss of appetite
Bleeding
12
Q

How is H. pylori infection treated?

A

Currently no therapy that is 100% effective for H.pylori infection

Successful therapies for H.pylori consist of 2 to 4 drugs given for periods of 7-14 days - must have efficacy of >80-90% in clinical trials.

Routine treatment of + ve asymptomatic patients NOT recommend Exceptions patients with :

  • Relatives with gastric cancer,
  • Infected spouses of a patient reinfected with H.pylori
13
Q

What are the problems with treating H. pylori infection?

A

Several barriers to antibiotic therapy:

	i) acidity of intestinal environment                                                                                              	
 		ii) inability of drugs to penetrate gastric mucus layer

Relies heavily on patient compliance

1/2 world’s population is infected - widespread treatment could cause resistance problems - already metronidazole & clarithromycin resistant strains

Undesirable side-effects can include diarrhoea, nausea & vomiting