Download Helicobacter pyloripupile

Dr.Wasan Sami
Helicobacter pylori
Helicobacter pylori is now considered to be the most prevalent infectious diseases
known to occur in humans; about 50% of the human population is estimated to be
infected, causing great discomfort to tens of millions and death to at least a million
per annum. H.pylori is usually acquired in childhood, and human the only important
reservoir of H.pylori. The prevalence of infection varies greatly among countries and
among population groups with in the same area.
Helicobacter pylori is spiral-shaped, Gram-negative rod , non spore former, actively
motile with mono polar multiple flagella, in prolong culture , it became coccobacilli.
H.pylori is associated with antral gastritis, peptic ulcer and strongly associated with
gastric cancer.
Transmission:
Mode of transmission by feco-oral, oral-oral, gastro-oral route, animals, raw
vegetables, water and water contaminated food.
Virulance factors of H.pylori
1- Flagella: allow the bacterium to swim across the viscous gastric mucus and reach
the more neutral pH underneath the mucus.
2-Bacterial adhesions
3-Lipopolysaccaride (endotoxin) associated with production of peptic ulcer
4-Enzymes: urease, arginase, catalase, oxidase, alkaline phosphatase, protease,
phospholipase.........etc.
5-Toxins:a) Vacuolating cytotoxin (VacA): induces vacules information in
eyokaryotic cells.
b)Cytotoxin-associated antigen (cagA): associated with inflammatory tissue response.
Pathogensis
H.pylori grows optimally at a pH of 6-7 and would be killed or not grow at the pH
within the gastric lumen. Gastric mucus is relatively impermeable to acid. On the
lumen side of the mucus, the pH is low 1-2 while on the epithelial side the pH is about
7.4. It is found deep in the mucus layer near the epithelial surface. H.pylori produces a
protease that modifies the gastric mucus and further reduces the ability of acid to
diffuse through the mucus, and H.pylori produces potent urease activity, which yields
production of ammonia and further buffering of acid. This bacterium is quite motile,
even in mucus, and is able to find its way to the epithelial surface. Ingestion of
H.pylori resulted in development of gastritis and hypochlorhydria. There is a strong
association between the presence of H.pylori infection and duodenal ulceration.
Antimicrobial therapy results in clearing of H.pylori and improvement of gastritis
and duodenal ulcer disease.
Toxins and lipopolysaccaride may damage the mucosal cells, and the ammonia
produced by urease activity may directly damage the cell also.
Histologically, gastritis is characterized by chronic and active inflammation.
Polymorphonuclear and mononuclear cell infiltrates are seen within the epithelium
and lamina propria. Vacuoles within cells are often pronounced. Destruction of
epithelium is common, and glandular atrophy may occur. H.pylori thus may be a
major risk factor for gastric cancer.
Clinical findings:
The signs and symptoms are those of gastritis and duodenal ulcer disease. Many
patients with H.pylori infection are asymptomatic.
Lab.diag.
Specimens:a)Gastric biopsy specimens can be used for histological examination,
culture and PCR.
b)Blood is collected for determination of serum antibodies
c)Stool specimens can be used for PCR or used to detect specific H.pylori antigen by
ELISA test.
Collection, transport and storage of specimens
H.pylori rapidly lose its viability at room temperature, therefore biopsy specimen
should be plated with 2 hours. Also H.pylori is sensitive to desiccation; so transport
media ( Brucella broth + glycerol) should be used.
Microscopy
H.pylori can be seen in histological sections by Giemsa or Gram stain or special
silver stain.
Dignostic methods
Dignostic methods of H.pylori can be classified into two types:
1-Invasive methods: Which require endoscopy to obtain biopsies for urease test,
culture, histology and PCR (in vitro).
2-Non invasive methods: These methods based on the detection of antibodies to
H.pylori or urea breath test ( in vivo) or ELISA test to detect specific antigen of
H.pylori .
1-Invasive methods
a) Histological examination:
It is a gold standard methods for the diagnosis of H.pylori. It is based on the
morphological appearance of the organism using Hematoxylin Eosin stain (H&E) or
Giemsa stain or special silver stain.
b)Culture
H.pylori grows in 3-6 days when incubared at 37Cْ in microaerophilic environment
with 5-10 %CO2, 80-90% nitrogen and 5-10%O2 and high humidity are required for
growth. They grow on chocolate agar and campylobacter media or skirrows media,
but those media should be supplied with either horse serum or sheep blood for
cultivation of H.pylori, also recommended to add three antibiotics (vancomycin,
polymyxin, trimethoprium) to make the media selective for the isolation of H.pylori.
Colonies are circular, convex, translucent and less than 2mm in diameter. All
helicobacter are oxidase positive, catalase positive, urease positive and produces
multiple enzymes such as DNA-ase, alkaline phosphatase and glutamyl
aminopeptidase …..etc.
c)Rapid urease test
H.pylori produces abundant urease which is 100 times greater than Proteus vulgaris .
It turns urea broth to pink color in few minutes. This test is based on the ability of
H.pylori urease to convert urea to ammonia with a resulting shift in pH causing a
change is detected by indicator phenol red.
Gastric biopsy
bacteria
CO2 + Ammonia
(pink color)
Urea broth + phenol red
(yellow color)
d) Polymerase chain reaction (PCR): PCR is highly sensitive technique that can used
to detect the presence of H.pylori in body fluids and tissue.
2-Non invasive methods
a) Serodiagnosis: Several assays have been developed to detect serum antibodies
specific for H.pylori. The serum antibodies persist even if the H.pylori
infection is eradicated, and the role of antibody tests in diagnosing active
infection or following therapy is therefore limited.
b) Urea breath test (in vivo)
The patient ingests a small quantity of urea in which the carbon is labeled with
either C13 or C14. If H.pylori is present in the stomach, the urea is hydrolyzed
by urease enzyme into ammonia and labeled carbon dioxide. Labeled carbon
dioxide is then measured in the patient's exhaled breath. This test is the best
method for detection of an active H.pylori.
c) Stool test
This test is used to detect specific H.pylori antigen by commercially available
enzyme immunoassay. It is an easy and a reliable test with sensitivity and
specificity reaching 94% and 91% respectively.
Treatment
Triple therapy that usually includes metronidazole, a
amoxicillin or tetracycline.
bismuth salt, and either