HELICOBACTER PYLORI Flashcards
(42 cards)
what is the history of heliobacter pylori ?
1984 the microbiology department of the royal perth hospital isolated a culture of spiral shaped bacterium from gastric biopsies of patient with gastritis
dr robin warren and dr barry marshal
Helico —> helical/spiral structure
bacter ——-> bacteria
pylori —-> pylorus of the stomach
H. pylori is responsible for what in the world ?
90% Of duodenal ulcers
80% of gastric ulcer
70% of gastric cancer
describe the epidemiology of H. pylori ?
H. pyolori infection occur worldwide
overall prevalence strongly correlates with socio-economic conditions
in developing countries prevalence is 80% in the industrialised countries 20-50%
over 80% of individuals infected infected with bacterium are asymptomatic
infection is acquired very early in childhood
infection can be cured appropriate diagnosis and treatment with antibiotics
H. pylori has an important role in protecting from some disease
over half of the worlds population is infected with H pylori ( but most are asymptomatic )
Large geograpical variations
how is H. pylori acquired?
oral ingestions of the bacterium
how is H.pylori transmitted?
within families in early childhood , via contaminated food
not isolated from water ( not water )
H. pylori protect against which disease ?
acid reflux disease
barretts esophagus
Esophageal cancer
how is the Prevalence of H. pylori studied?
mass screening is done for antibodies ( ELISA) –> IgG antibodies are tested
what are the risk factors for acquisition of H . pylori ?
infected family member
crowded living condition
poor hygiene
siblings more than 2
poor sanitation
fecal contamination of water supply
health care professionals ( contaminated hands and so on )
what are the characteristics of helicobacter pylori ?
Gram - , rod , curved
very motile —> flagella
microaerophilic ( helicobter is a small plan so micro aero plane )
grow at body temp ( 37 )
what is microaerophilic microorganism ?
require environments containing low levels of dioxygen than that are present in the atmosphere for optimal growth
what are the virulence factors for H. pylori?
highly motile —> corkscrew motility
produce abundance of urease
what is the importance of urease ?
break down urea into ammonia and CO2
The amonia will neutralize the acidic envirtonment
and destroy the mucus
Allowing the pathogen to survive the acidic environment
what is the important of flagella and corkscrew motility ?
allow the pathogen to push through the mucosa into submucosa where it can create an alkaline environment
survive the acidic environment
describe the process by H. pylori causes ULCER?
H. pylori penetrate the mucous layer lining the stomach epithelium , attracted to the chemotactic substance hemin and urea
2- it recruits and activate inflammatory cells , release urease that cleaves urea producing NH3 ( ammonia ) which neutralizes the stomach acid in the vicinity
3- cytotoxic and the ammonia produced by its urease cause destruction of mucus producing cells exposing underlying connective tissue to stomach acid —> ULCER
what are the other virulence factors ?
Exotoxin —> Vacuoulating toxin (vacA)
CagA protein
lipopolysaccharides —> adhere to host cell inflammation
outer proteins —> adhere to host cells
secretory enzymes —> mucinase , protease, lipase —> gastric injury
Type IV secretion system : pill like structure for injecting effectors
what does vacuolating cyotoxin A do ? VacA?
protein that after penetration into epithelial cells damage the cells by producing vacuoles
what does cytotoxin associated gene do ? (cagA )
induce IL-8 —> enhance inflammation
apoptosis inhibition —> lead to cancer
loosens tight junctions
describe the progression H. pylori infections ?
Normal mucosa
chronic active gastritis —> immune response , diet, gastrin, host genetics
Gastric atrophy —> achlorhydria , carcinogen
Intestinal metaplasia
dysplasia
gastric cancer
what are the possible clinical outcomes?
80% —> asymptomatic or chronic gastritis
15-20% —-> chronic atrophic gastritis , intestinal metaplasia + Gastric or duodenal ulcer
1% —-> Gastric cancer / MALTS lymphoma
NO h.pylori , no ulcer , no cancer
what are the clinical manifestation of H. pylori?
bloating
loss of appetite
nausea
passing gas
gnawing pain
Burning
bad breath
belching
Vomiting
loss of appetite
what are invasive tests for diagnosing H. pylori ?
Histology - gold stander
culture for confirmatory
Rapid urease test
molecular —> research
Require —> gastric endoscopy and tissue biopsy
what are non invasive tests to diagnose H. pylori ?
Serology — > antibody detection
urea breath test
stool antigen test
what are the advantages and limitations of culture test?
Advantages :
Evidence of active infection
antimicrobial susceptibility testing possible
highly specific
Limitation :
Sensitivity affected by : site of biopsy and bacterial load, viability of organism during transport
Not routinely available
what are the advantages and limitation of rapid urease tests ? RUT?
Advantages :
Evidence of active infection
Rapid
high sensitivity and specificity (90% + )
Limitations :
Sensitivity affected by : site of biopsy and bacterial load, viability of organism prior to testing, prior use of PPIs, bismuth, antibiotics
Specificity may be affected by presence of urease from other helicobacter species
