ph102 3
Terms
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- Epidemiological Triad
- agent, host, environment
- endotoxins
- bound to cell membrane; usually in gram negative bacteria; very powerful toxins
- Intracellular pathogens
- ability to survive within the host cell
- Koch's Postulates 3
- Inoculation of the pure culture should result in a similar disease
- fecal-oral spread
- salmonella and shigella
- antigenic variation
- changes in the amino acid composition of a surface protein
- Koch's Postulates 2
- Should be grown in pure culture on artificial media
- determinants of virulence
- allows the parasite to invade and damage the host and to resist the defenses to the host
- avoiding phagocytosis
- Capsules, toxins, extracellular enzymes, antigenic variation
- Resistant to drying
- spore strategy
- Koch's Postulates 1
- Organism should be found in all cases of the disease
- phase variation
- switch on or off the expression of some bacterial cell component
- Two main virulence mechanisms
- Invasion and Toxin production
- Extracellular pathogens
- phagocyte avoidance mechanisms
- surviving on skin surfaces
- gram positive organisms strategy
- Koch's Postulates 4
- It should be possible to recove the agent from the lesions of the experimental disease
- exotoxins
- toxins secreted outside the cell
- surviving in fluids
- gram negative organisms strategy