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20 Cards in this Set
- Front
- Back
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How can we tell if a microorganism is responsible for an illness? |
Koch's Postulates: -It is found in ALL patients with the disease -It is found in the affected organ -A pure culture of the agent can infect a healthy animal or volunteer -The same microorganism can be isolated from that animal/volunteer |
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What are the two kinds of pathogens? |
-Strict pathogens -Opportunistic pathogens |
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Pathogenic strains are members of a species that is either ___ or ____. Explain what that means. |
Commensal (frequent) - E. coli, S. aureus. Organisms that live/evolve with the host and are usually non-pathogenic. Saprophytes (infrequent) - P. aeruginosa. Feed off of decay. |
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A pathogen must be able to: |
-Be transmitted to a new host -Colonize or invade the host -Grow on or in the host -Escape host defenses -Damage the host |
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Name the 5 routes of entry for pathogens |
1) Oral 2) Respiratory 3) Cutaneous 4) Transcutaneous 5) Sexual Transmitted directly or indirectly. |
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Role of Fimbriae in pathology? |
Sticking to the host cell initiates pathogenic colonization. |
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Why do they do it? What is one important resource bacteria get by colonizing a host cell? |
-IRON. Almost no free iron in extracellular fluids. They have high affinity siderophores that can strip iron from the host cell. |
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How can pathogens avoid host defenses? |
-They can avoid phagocytosis, via a bacterial capsule. -They can survive INSIDE the phagocyte, escaping the phagolysosome. -Some can even survive IN the phagolysosome. |
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How do pathogens harm the host? |
Via production of hydrolytic enzymes. -Collagenase: Clostridiumsp -Hyaluronidase: Staphylococcussp,Streptococcussp -Elastase: Pseudomonasaeruginosa -Coagulase: Staphylococcusaureus -DNase: Staphylococcussp,Streptococcussp |
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What do the hydrolytic enzymes do? |
-Collagenase/Hyaluronidase/Elastase: break down extracellular matrix, facilitating pathogen spread -Coagulase: forms fibrin clot that isolates pathogen from phagocytes -DNase: clears cell exudate and facilitates pathogen spread |
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Name the two different categories of toxins |
-Exotoxin (secreted proteins) -Endotoxin (LPS): produce systemic effects, can hyper-stimulate immune response and lead to septic shock |
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How do we measure virulence? |
Via the LD50 test (how much expose will kill off half of the population?) and ID50 (the dose of an organism required to infect 50% of the population). |
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What do specific host antibodies do? |
-Block adhesion to host cells -Block iron transport -Inactivate exotoxins |
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State the 1957 Lwoff requirements used to identify a virus |
-Diameter <250 nm -Obligatory intracellular parasites -No enzymes for energy metabolism -Particles only contain one type of nucleic acid: RNA or DNA but never both -Do not replicate by binary division -Absence of ribosomal RNA, the most conserved molecule ever!!!! |
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Name two different kinds of capsid symmetry within viruses |
1) Helical symmetry (rod shaped) 2) Icosahedral symmetry (complicated soccer ball shaped) |
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Explain what a Plaque Forming Unit (PFU) is |
A plaque is what happens when a virus infects and lyses a cell. One plaque corresponds to one infectious virus particle OR one infected bacterial cell. |
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List the phases of viral infection |
1) Attachment 2) Entry 3) Decapsidation --> Eclipse Phase 4) Genomic replication --> Eclipse Phase 5) Gene expression --> Eclipse Phase 6) Assembly 7) Release |
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What is the difference between a lytic and lysogenic cycle? |
The lytic cycle is immediate - the phage infects the host, reproduces itself, and bursts out, lysing the cell. The lysogenic cycle is sneaky - the phage infects the host, and the viral DNA is incorporated into the host genome, lying dormant until activated. |
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How does viral attachment/entry work? |
Each phage has a unique attachment protein that allows it to attach to a specific species of bacteria. It enters via local disruption of the bacterial cell wall, injecting genome in like a big needle. |
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Explain the lambda phage's unique ability to perform the lytic and the lysogenic cyle |
All revolves around the CII protein. This CII protein only allows the transcription of CI and integrase genes only - CI catalyzes incorporation into the host genome and inhibiting phage late genes (destroy cell). However, in most cases CII is degraded by the host cell, preventing the inhibition and cuing the lysis of the host. |
