5. Gastritis and Viral Gastroenteritis Flashcards
Helicobacter pylori Properties
- Gram -ve comma/S/spiral shaped
- Multiple flagella at 1 pole
- Motile
- Microaeorphile
- Oxidase, catalase & urease +
Helicobacter pylori Transmission
- Natural habitat: Human stomach (prob. ingested)
- Person to person
Helicobacter pylori Pathogenesis
- 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
Helicobacter pylori Clinical Findings
- 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
Helicobacter pylori Diagnosis [3] [6]
-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
H. pylori
1- Urea Breath Test
- Initial diagnosis/confirmation of eradication
- Radiolabeled urea > urease cleave urea > radiolabeled CO2 detected (+)
- More senstivite if PPI usage stopped for 2 weeks
H. pylori
2- Stool antigen
- Initial diagnosis/confirmation of eradication
- Test by enzyme-linked immunosorbent assay
H. pylori
3- Serum IgG antibodies againsat H. pylori
+ve result indicates exposure to H. pylori
can’t tell if current/past
(antibodies persist after recovery)
H. pylori
1- Gram stained smear
gastric biopsy
gram -ve
H. pylori
2- Rapid Urease Test
Gastric biopsy > medium w/urea + coloue indicator > urea NH3 (1-2hrs) > ph changes > medium changes colour (yellow to pink) = +
H. pylori
3- Histological examination
Hematoxylin & eosin, modified Giemsa stain or Warthin-Starry silver stain
(slender curved bacilli)
H. pylori
4- Immunohistological staining
Mono & Polyclonal antibodies immunohistological staining improves senstivity & specificity of detection
H. pylori
5- Cell culture
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
H. pylori
6- PCR
- Highly sensitive & specific - rapid result w/ resitance info (mutations)
- Limited use
Caliciviruses; Norovirus; Norwalk virus Properties
- Nonsegmented +ssRNA
- Nonenveloped w/icosahedral nucleocapsid
- No polymerase
- E. microscope > 10 spikes & 32 cup-shaped depressions
- 6 genotypes (mostly genogroup II > human infections)
Caliciviruses; Norovirus; Norwalk virus Transmission process
- 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
Caliciviruses; Norovirus; Norwalk virus Transmission enhancers
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
Caliciviruses; Norovirus; Norwalk virus Pathogenesis
Limited to mucosal cells of intestinal tract
Caliciviruses; Norovirus; Norwalk virus Clinical Findings
- 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
Caliciviruses; Norovirus; Norwalk virus Lab Diagnosis
1- Clinical Picture
2- PCR on stool
Reoviruses & Rotaviruses Properties
- Segmented (11), dsRNA surrounded by x2 icosahedral capsid
- Contains RNA-dependent RNA polymerase
- 6 serotypes
- Outer surface protein (viral hemagglutinin) - type specific
Reoviruses & Rotaviruses Transmission
Fecal-oral route
Reoviruses & Rotaviruses Pathogenesis
- Replicate in SI mucosal cells
- Excess fluid & electrolyte secretion into bowl lumen
- 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
Reoviruses & Rotaviruses Virulence
- Genes control tissue tropism & inhibition of cell RNA & PS
- Intestinal IgA prevents reinfection of certain serotypes
- Colustrum IgA protects newborns up to 6 months
Reoviruses & Rotaviruses Lab Diagnosis
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)
