Genus Helicobacter. H. Pylori

Question 1

Classification

Answer 1

Family: helicobacteriaceae

Genus: Helicobacter

At least 23 species

Most important:

Helicobacter pylori

Resides in the human stomach (near the pylorus)

Question 2

Morphology

Answer 2

Gram-negative rod

Curved (helical shape)

Motile: peritrichous flagella

Question 3

Growth characteristic

Answer 3

Microaerophilic

Fastidious

Urease positive:

• urease breath test
• biopsy

Oxidase and Catalase positive

Question 4

Antigenic structure

Answer 4

O antigens

Flagella antigens

Question 5

Virulence factors

Answer 5

> > Outer membrane proteins:
1) Adhesins protein: adhesion to host cell

2) Porins proteins, iron transporters, and flagella proteins

> > Somatic O antigen:

Mimic Lewis blood group antigen found on the gastric epithelium

> > Exotoxins: vacuolating (Vac A) toxins—>
Gastric mucosal injury

> > Secretory enzymes:

1) Urease: neutralize gastric acid —-mucosal injury
2) Mucinase, lipase, protease: mucosal injury

> > Flagella: motility

> > cytotoxic associated gene A (Cag A): cause uncontrolled host cell growth and apoptosis inhibition

Question 6

Disease

Answer 6

• gastritis
• duodenal (peptic) ulcer —> 95%
  Complications: increased cancer risk
  > Adenicarcinoma of the stomach
  > mucus associated lymphoid tissues (MALT) lymphoma

Question 7

Microbiological diagnosis

Answer 7

Gram stain and culture
Urease positive
Oxidase positive
Serologic tests for antibody and the “urea breath” tests are useful

Question 8

Treatment and prevention

Answer 8

1st line:

Proton pump inhibitor

Antibiotics:

• amoxicillin + claritromycin (macrolide)
• metronidazole + clarithromycin (macrolide) —> penicillin allergy

Prevention
No vaccination