Helicobacter Pylori Flashcards
How helicobacter pyori are transmitted?
By ingestion of food or water
What is the clinical presentation?
Chronic inflammatory gastritis = duodenal ulcer
What are their virulence factors?
Urease, motility, adherence factors, heat labile cytotoxin, gastric mucin protease, hemolysin, lipopolysaccharides
What’s the importance of the adherence factors?
For colonization
Which 2 different products are coded by the bacterial chromosome?
One product has a cytotoxic activity, the other has a vacuolating activity of glands, leading to their atrophy
What’s the importance of the gastric mucin protease?
To buffer the pH of the gastric mucin
What’s the function of hemolysins?
Break down RBCs
What is the optimal pH? Which part of the stomach has this pH?
Their optimal pH is 7
The mucosa of the stomach is the area of optimal growth of H. pylori
What is the site of infection during the acute stage? Where bacteria colonize?
The gastric antrum
Bacteria are present in the mucus overlying the mucosa. Colonization extends to the gastric glands but the mucosa isn’t invaded by bacteria
What is the outcome of the acute stage?
There is a superficial active gastritis infiltrated with inflammatory cells and PMN
What does the hemolysin?
It breaks the hemoglobin releasing hemin
How the medium become more alkaline and protecting the bacteria?
Ammonia by urease activity covers the bacteria to make the medium more alkaline, along with the gastric mucin protease, this creates a buffering, protecting the bacteria.
What are the symptoms of the acute stage?
Acute achlorhydric gastritis, nausea, abdominal pain, flatulence and bad breath because of the ammonia
When there is a progression to chronic gastritis and atrophic gastritis?
When achlorhydric gastritis stays for a year even after recovery
Which virulence factors are associated with the bacteria in peptic ulceration during the chronic stage?
Vac A (vacuoating protein) and Cag A (cytotoxicity associated protein)
What can influence the outcome of infection during this stage?
Host factors like age (when age increases infection increases), how many times we have been infected and if we had developed Ab
Where are present genes for Vac A and Cag A?
on the pathogenicity island of H. pylori.
Where the bacteria invades? What is the outcome?
To lower layers
There will be atrophic gastritis
What will happen if individuals don’t take the proper treatment?
Manifestations would last longer, especially abdominal pain and achlorhydric gastritis
Where bacteria invades during gastric cancer?
Bacteria are no more between the mucus layer and the mucosa, they invade the mucosa layer
What causes the formation of cancer?
Bacteria will multiply for a short period, they direct the cells causing them to replicate
Why antibiotics or no longer effective in this period?
Since bacteria will disappear after that cancer is established
Which type of cancer we will have?
MALT lymphoma
What’s the cure when individuals reach the stage of cancer?
Once cancer state is reached there is no longer cure
What is done to make the invasive tests?
A biopsy is taken from the pyloric end of the stomach or the surrounding by 5 cm. We use a part of the biopsy for each test
For which tests the biopsy is used?
Histopathology and microscopy
Culture
Biopsy urease test
What is the importance of histopathology even when bacteria can’t be found?
It allows us to see the tissue changes during carcinoma
On which medium H. pylori can grow?
On blood agar plate
What are the results of the oxidase and catalase tests?
Oxidase positive and catalase positive
Are they gram negative or positive?
What is their shape?
They are gram-negative spiral bacteria
Where biopsy is put in the biopsy urease test?
A piece of biopsy is put into urea with an indicator
What indicates the presence of urease?
If there is a pH change, there was production of ammonia, so there is urease
Why biopsy urease test is better than culture and histopathology?
Since it is a very quick method that gives results within 2 hours
Which one are non-invasive tests?
Serology
Urea breath test
Fecal antigen test
PCR
Which test is used in serology? Which antibodies are detected?
ELISA to detect certain Ab (IgM, IgG, IgA) against certain antigens
What is the procedure of the urea breath test?
What happens if H. pylori is present?
The patient swallows in a capsule containing an isotope of carbon C13 or C14
If H. pylori is present, the isotope will be in the exhaled CO2 (urea + water + urease —> CO2 + ammonia). For detection, we need a spectrophotometer.
What is the danger concerning this test?
The danger is that C14 is radioactive
The test is not as easy as the biopsy urease test, though it is not invasive
What detects the fecal antigen test?
We have kits containing Ab to different Ag to detect H. pylori antigens in fecal specimens.
It gives quick results.
Which specimens can be taken for PCR?
Saliva, dental plaques, water and fecal specimens
Is there production of protective Ab after the first time of infection?
No protective Ab after the first time of infection
When protective Ab are produced?
At which age individuals become protected?
The second time of infection
At the age of 60, enough Ab are produced so individuals are protected. It is an additive effect.
What’s the antibiotic treatment?
Is there any vaccine?
A combination of 3 drugs for at least one week: omeprazole (which is a proton lowering pump inhibitor, increases the activity of the 2 other antibiotics, it is not an antibiotic but a drug), Clarithromycin and metronidazole
No vaccine
