Exam 4: Intestinal Bacteria
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• lives in stomach • wants to live in neutral area • live in epithelia because mucus makes it less acidic
hylobacter pylori
what are koch’s postulates?
• infectious agent must be found in the diseased individuals and not in healthy individuals • grow infectious agent in pure culture • recapitulate disease in model host with pure culture • needed to recapture pathogen • if you can remove infectious agent, you should be able to get rid of disease
does H. pylori follow Koch’s first postulate?
no because it is found in both sick and healthy individuals
what are non-invasive ways to look for H. pylori?
• serology test • ELISA (enzyme linked immunosorbent assay) • urea breath test
• looks for antibody that responds to pathogens in patients - if antibodies are there, pathogen must be there
serology test
• type of serology test - if there are more antibodies present, there is greater color intensity of the assay
ELISA
• breaks down urea into CO2 and NH3 - H. pylori has it
urease
how does the urea breath tes work?
give 13C-urea or 14C-urea to patient and look for 13C-CO2 or 14C-CO2 in breath
what are invasive methods of looking for H. pylori?
• biopsy • microscopy • gram staining (H. pylori Gram -, spiral shape, motile)
how can H. pylori be grown in pure culture?
• it is microaerophilic • prefers 2-5% oxygen and 5-10% CO2 • takes 5-10% of blood (sheep, horse)
how do you recapitulate a disease in a model host with pure culture?
• multiple cell lines - primary cells
-usually immortalized by viruses or derived from cancer cells ~in gastric epithelium
multiple cells lines
have a limited life span
primary cells
what poses a threat for H. pylori?
• acid • peristalsis • muscosal barrier • immune detection
how does H. pylori deal with acid?
• urease - proton driven pump that transports urea into cells to neutralize acid
how does H. pylori deal with peristalsis?
• gets to epithelium with chemotaxis (flagella) - rotates, corkscrew motion to penetrate mucus
during chemotaxis, what does H. pylori move toward and away from?
• moves away from acid (H+) - moves toward amino acids
when is H.pylori able to penetrate the mucus the fastest?
when the environment is viscous
how does H. pylori deal with the mucosal barrier?
• BabA - SabA
• attach to our blood group antigens - binds to fucose
BabA
• attach to our blood group antigens - binds to things with sialic acid
SabA
what is the gene protein of non-secretor people?
Le
what is the gene protein of secretor poeple?/
Le + Se
what is the antigen of non-secretor people?
substrate + fucrose