Glossary of MicrobiologyChapter 34
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- What are pathogens, Opportunistic pathogens, etiologic agents.
- Pathogens-the causative (etiologic) agent.
Opportunistic Pathogens-host pathogens may become pathogenic under certain circumstances(immune system compromised).
etiologic agent-causes the disease.
- pathogenesis, virulence, infections, and intoxications?
- Pathogenesis-The process of causing disease.
Virulence-the intensity of the disease caused.
Infections-When a parasite is growing in or on the host
Intoxications-Disease resulting from the entrance of a specific toxin into the body of a host. The toxin can produce the disease in the absence of the toxin-producing organsim (bad guy)
- How do we measure the virulence of a pathogen?
- Virulence measured by LD50 or ID50. (Inject 100 mice with 100units of organism and 50 will die)
- What are the three determinats of virulence? What are virulence traits (determinants)?
- Infectivity-the ability to establish an infection.
Invasiveness-the ability to spread within the body.
Pathogenic potential-the ability to cause damage.
- How can a virulence trait affect and get into the host
- Direct-cough, bumping uglies
Indirect-airborne, water, letters
- How can a virulence trait affect and gain access to the host site?
- Ectoparasites-remain on host surface
Endoparasites-invade/enter host tissues by passive (vectors like flea or trama like nail) or Active-Induced uptake(Salmonella type III secretion system) like needle sticks it in and pumps proteins into host tissue which allow host cells to take up the virulence.
Spread within the host-Spreading factors, Blood-lymphatic-nerve tracts-mucosal secretions, Tropisms are tissue specificities (receptors)
- How can a virulence trait affect and colonize a host site?
- Attach to the host and reproduce. Adhesins required for areas of flow-adapt to growth conditions.
Need to obtain nutrients-acquisition of Fe.
- How can a virulence trait affect and defeat host defenses?
- Evasion of complement, Resisting phagocytosis, Survivng phagocytosis, Antigenic variation, Phase variation aIgA proteases, Binding Ig by Fc.
- How can a virulence trait affect and damage the host?
What are two ways other then a toxin that a microb may damage its host?
- Host response-virulence gone, but your body still acting on it.
Growth within the cell-
- How can a virulence trait affect and escape from the host?
- Cough, Diarrhea
- What role has horizontal gene transfer played in the development of pathogens?
- Transfers from one organism to another adds to mutation and variations-antibiotic resistance.
- What are pathogenicity islands?
- clusters of virulence genes on chromosomes. They are acquired en bloc by horizontal transfer (flanked by IS elements, diff G+C ratio, Distinguish pathogenic strains)
- How do bacteria regulate their virulence genes?
- Virlence genes must be regulated-bacteria live in diff environs, need diff traits in diff stages of an infection
- How do exotoxins differ from endotoxins?
- Exotoxins-secreted proteins that cause damage to or dysfunction of the host. Often encoded on extrachromosomal elements.
Endotoxins-Lipid A of LPS.
- Can you describe an example of an AB type toxin? What do each of its subunits do?
- B-binds and promotes entry through cell or vacuolar membrane for A-active, enzymatic which modifies host structure.
Example: Diphteria toxin-AB cleaved and ADP-ribosylates all EF-2 which prevents cell from protein sythesis=cell death
- What are two types of membrane-disrupting toxins?
- Two types of membrane-disrupting toxins are pore-forming toxins and phospholipases.
- What are superantigens?
- Superantigens are bacterial proteins that stimulate the immune system much more extensively than do normal antigens.
- What are four broad pathways by which endotoxins exert their effects?
- Four broad pathways by which endotoxins exert their effects are by clotting (hemorrhage), fibrinolysis (break down of clots=more hemorrhage), complement activation (inflammation), and kininogen system (release vasoactive substances=shock).
- Give examples of evasion of complement
- Three examples of bacterial evasion of host complement are sialic acid capsules (stops ACP), Long LPS, and addition of host sugars to LPS.
- Give examples of resisting phagocytosis
- Bacteria resist phagocytosis by host cells by having capsules (prevent opsonization), producing C5a protease (prevents chemotaxis), and secreting leukocidins (kill phagocytes).
- Give examples of surviving phagocytosis
- Bacteria survive phagocytosis by escaping from the phagosome, inhibition of fusion with lysosome, and surviving the lysosome.
- Give examples of antigenic variation
- Antigenic variation is random changing of antigenic determinants to avoid the immune response. An example of this is Neisseria gonorrhoeae which changes its pilus antigens.
- Give examples of sIgA protease
- Two examples of sIgA protease are in N. gonorrhoeae adn Haemophilus influenzae.
- Give examples of Binding Ig by Fc
- An example of binding Ig by Fc is in Staph aureus protein A.
- How does antigenic variation differ from phase variation?
- Antigenic variation is the changing of antigenic determinants while Phase variation is teh turning on or off of an entire antigen.
- Do they occur in response to a stimulus? Why?
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