5. Gastritis and Viral Gastroenteritis

Question 1

Helicobacter pylori Properties

Answer 1

• Gram -ve comma/S/spiral shaped
• Multiple flagella at 1 pole
• Motile
• Microaeorphile
• Oxidase, catalase & urease +

Question 2

Helicobacter pylori Transmission

Answer 2

• Natural habitat: Human stomach (prob. ingested)

- Person to person

Question 3

Helicobacter pylori Pathogenesis

Answer 3

• Attaches to mucus-secreting cells of gsatric mucosa
• Production of large amounts of NH3 w/inflammatory proteins
• Loss of mucus coating > Gastritis & Peptic ulcer
• NH3 neutralises stomach acid, allowing organism to live

Question 4

Helicobacter pylori Clinical Findings

Answer 4

- Gastritis & Peptic ulcer w/
	recurrent pain in upper abodmen
	bleeding into GI
- No Bacteremia/disseminated disease
- Gastric MALT Lymphoma from B-cell proliferation > Lymphoma*
*antibiotics regress tumor

Question 5

Helicobacter pylori Diagnosis [3] [6]

Answer 5

-Noninvasive (initial in <60 y/o w/dyspepsia)
1- Urea Breath Test
2- H. pylori stool antigen
3- Serum IgG antibodies against H. pylori
-Invasive (biopsies)
1- Gram stained smears
2- Rapid Urease Test
3- Histological examination (gold standard)
4- Immunohistological staining
5- Cell culture (Nonselective & Selective medias)
6- PCR

Question 6

H. pylori

1- Urea Breath Test

Answer 6

• Initial diagnosis/confirmation of eradication
• Radiolabeled urea > urease cleave urea > radiolabeled CO2 detected (+)
• More senstivite if PPI usage stopped for 2 weeks

Question 7

H. pylori

2- Stool antigen

Answer 7

• Initial diagnosis/confirmation of eradication

- Test by enzyme-linked immunosorbent assay

Question 8

H. pylori

3- Serum IgG antibodies againsat H. pylori

Answer 8

+ve result indicates exposure to H. pylori
can’t tell if current/past
(antibodies persist after recovery)

Question 9

H. pylori

1- Gram stained smear

Answer 9

gastric biopsy

gram -ve

Question 10

H. pylori

2- Rapid Urease Test

Answer 10

Gastric biopsy > medium w/urea + coloue indicator > urea NH3 (1-2hrs) > ph changes > medium changes colour (yellow to pink) = +

Question 11

H. pylori

3- Histological examination

Answer 11

Hematoxylin & eosin, modified Giemsa stain or Warthin-Starry silver stain
(slender curved bacilli)

Question 12

H. pylori

4- Immunohistological staining

Answer 12

Mono & Polyclonal antibodies immunohistological staining improves senstivity & specificity of detection

Question 13

H. pylori

5- Cell culture

Answer 13

1- Nonselective: Chocolate agar
(brain heart infusion & brucella agars w/horse or rabbit blood)

2- Selective: Thayer-Martin agar, Pylori agar, & Dent’s medium

2 to 5 days* at 37ºC w/low O2 levels (5-10%) & high CO2 levels (5-12%)
Small (1 to 2mm diameter), translucent, & nonhemolytic
Used when patient isnt responding to treatment
*Wait 10 days before reporting -ve

Question 14

H. pylori

6- PCR

Answer 14

• Highly sensitive & specific - rapid result w/ resitance info (mutations)
• Limited use

Question 15

Caliciviruses; Norovirus; Norwalk virus Properties

Answer 15

• Nonsegmented +ssRNA
• Nonenveloped w/icosahedral nucleocapsid
• No polymerase
• E. microscope > 10 spikes & 32 cup-shaped depressions
• 6 genotypes (mostly genogroup II > human infections)

Question 16

Caliciviruses; Norovirus; Norwalk virus Transmission process

Answer 16

• Fecal-oral route, ingestion of contaminated seafood/water
• Outbreaks occur in group settings
• Person to person transmission
• New strain appears every 2 to 4 yrs > widespread infection

Question 17

Caliciviruses; Norovirus; Norwalk virus Transmission enhancers

Answer 17

1- Low infectious dose
2- Excretion of virus in stool before symptoms & weeks after recovery
3- Resistace to inactivation by chlorination & drying

Infectious for several days in water, uncooked food & surfaces

Question 18

Caliciviruses; Norovirus; Norwalk virus Pathogenesis

Answer 18

Limited to mucosal cells of intestinal tract

Question 19

Caliciviruses; Norovirus; Norwalk virus Clinical Findings

Answer 19

• Watery diarrhea w/o RBCs or WBCs
• Sudden onset of vomiting, diarrhea, low-grade fever & abdominal cramp
• In some immunocomprimised > chronic gastroenteritis
• In some outbreaks > signs of CNS involvement such as
  Headache
  Meningism
  Photophobia
• 2 to 3 days & no sequelae

Question 20

Caliciviruses; Norovirus; Norwalk virus Lab Diagnosis

Answer 20

1- Clinical Picture

2- PCR on stool

Question 21

Reoviruses & Rotaviruses Properties

Answer 21

• Segmented (11), dsRNA surrounded by x2 icosahedral capsid
• Contains RNA-dependent RNA polymerase
• 6 serotypes
• Outer surface protein (viral hemagglutinin) - type specific

Question 22

Reoviruses & Rotaviruses Transmission

Answer 22

Fecal-oral route

Question 23

Reoviruses & Rotaviruses Pathogenesis

Answer 23

1. Replicate in SI mucosal cells
2. Excess fluid & electrolyte secretion into bowl lumen
3. Loss of salt, glucose, & water > non-bloody watery diarrhea
   - No inflammation
   - Watery diarrhea due to ENS stimulation
   - Worldwide infection by age 6, most kids immune to 1 serotype

Question 24

Reoviruses & Rotaviruses Virulence

Answer 24

• Genes control tissue tropism & inhibition of cell RNA & PS
• Intestinal IgA prevents reinfection of certain serotypes
• Colustrum IgA protects newborns up to 6 months

Question 25

Reoviruses & Rotaviruses Lab Diagnosis

Answer 25

1- Detection in stool (Radioimmunoassay or ELISA) - Practical
2- Desmonstration in stool by immunoelectron microscopy - Not practical
3- Fourfold (or more) rise in antibody titer
4- Culture (not routinely done)