Campylobacter and Helicobacter

Question 1

Please list three factors/mechanisms that are important for virulence and colonization of the human
stomach by Helicobacter pylori?

Answer 1

1. Adhesion (adhesins)
2. protection against gastric acid (urease)
3. immune evasion and supression (vacA)
4. helical shape and flagella for movement in intenstine

Question 2

VacA of H. pylori is a key example for a multifunctional toxin. Please list two mechanisms/roles of VacA
during H. pylori virulence.

Answer 2

1. dsirupts epithelial barrier
2. adhesin
3. Membrane channel activity
4. Inhibtion of T cell activation and proliferation
5. Vacuolation

Question 3

What are the most common sources of Campylobacter spp. infections?

Answer 3

Beef
poultry
Milk

Question 4

Please list two differences in colonization of human and chicken hosts by Campylobacter jejuni.

Answer 4

In humans there is colonic invasion, inflammation and diarrhoea while birds are asmptomatic only colonise mucous layer and doeant cause inflammation.

2. temperature. 36 vrs 41- 45 degrees celcius

Question 5

Campylobacter jejuni lacks a classical secretion system for injection of virulence factors into host cells.
How are proteins secreted by Campylobacter jejuni ? What type of secretion system does the
responsible cellular structure resemble?

Answer 5

1. Functional flagellar apparatus acts as a secretion machinery using cia and Fed proeteins.
2. some strains have T6SS.

the secretion system of c. jejuni flagella resmbles that of type III secretion systems.

Question 6

Please describe the composition and mechanism of action of the cytolethal distending toxin (CDT) of
Campylobacter jejuni.

Answer 6

Cdt-A: accesory
Cdt-B: catalytic active component
Cdt-C: assesory

induces IL-8 in the intestine causing inflamation.
it aslo induces coleorectal tumorgenesis

Question 7

What are the three surface structures important for virulence of Campylobacter jejuni? What is the
molecular basis for the Guillan-Barré Syndrom that can occur as a sequelae during Campylobacter
jejuni infection

Answer 7

a. Lipoologosaccharide, capsule, flagella
b. Gullian-Barre syndrom is caused by molecular minicry of human gangliosides. Campylobacter contains ganglioside-like epitopes in the lipooligosaccharide moiety that elicit autoantibodies reacting with peripheral nerve targets.

Question 8

Campylobacter and Helicobacter have numerous „homopolymeric simple sequence repeats“ in their
genomes. Please describe two mechanisms how such repeats can lead to differential gene expression.

Answer 8

Slipped strand mispairing –> insertion or deletion resulting in one strand being longer
o Intergenic SSR: in promoter elements, can change spacing between -10 box and -35 box, affecting transcription
o Intragenic SSR: can cause frame-shift mutations, affecting translation

Question 9

How can Helicobacter infections be diagnosed and what is the most common therapy?

Answer 9

• Biopsy check durring endoscopy- urease test, histology and microbial culture.
• carbon urease test
• blood antibody test
• stool antigen test

Most common therapy is the thripple therapy
#Amoxicillin
#Clarithromycin
#proton pump inhibitor (omeprazole)

or a quadripple therapy which adds a bismuth subsalicylate.

Question 10

Which enzyme facilitates survival of H. pylori in the acidic environment of the human stomach and
what is it underlying molecular mechanism?

Answer 10

Urease
Hydrolysis of urea into cabon dioxide and ammonia
(NH2)2CO + H2O → CO2 + 2NH3