Spread/transmission of infectious disease Flashcards

1
Q

what is virulence and infectivity

A

virulence- Ability to cause host cell damage

Infectivity- Ability to infect and colonize host

inverses of eachother

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2
Q

Measureing Virulence:

what is LD50 and ID50

A

LD50- the # of microorganisms needed to kill half of hosts (lower the more deadly)

ID50- the # of microorganisms needed to cause infection in half exposed

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3
Q

What are the 4 virulence factors

A
  1. adherence ability
  2. Evasiveness
  3. Invasiveness
  4. production of toxins
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4
Q

What is invasiveness and what do less and higly invassive organisms cause

A

ability to spread within the host (aided by invasins)

Less invasive organisms cause localized lesion
highly invasive organisms cause generalized infection

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5
Q

What is the function of 1) hyaluronidase + collagenase + 2) coagulase + kinase as invasins

A

1) break down collegen layer of epithelial cells so it can invade deeper
2) coagulase will create clot so it can surround and hide microorganism, kinase will break down clot after in the blood stream

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6
Q

What are mechanisms of evasiveness

A
  1. tolerence to barriers
  2. blocking attachment with phagocyte
  3. Block phagocyte opsonins
  4. blocking fusion with phagocyte
  5. escaping phagocyte cytoplasm
  6. producing bacterial antioxidents
  7. Prod of toxins that kill phagocytes
  8. Prod proteases that break down antibodies
  9. use latency
  10. opa proteins inhibit t helper cells
  11. surface antigens
  12. Tegument (outer body covering)
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7
Q

what is an exotoxin vs an endotoxin

A

exotoxin- secreted by bacteria

endotoxin- a part of the cell wall of gram negative bacteria. Will release upon lysis of cell

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8
Q

what do hyaluronidase and collegenase exotoxins do

A

hyaluronidase- degredes hyaluronan found in layers of epidermis that connects cells

collagenase- degrades collagen bw endothelial cells allowing bac to enter bloodstream

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9
Q

What do alpha toxin exotoxins do

A

creates pores in cell membrane causing hemolysis and tissue damage

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10
Q

what does diptheria toxin do

A

inhibits cell pro synthesis and kills susceptible cells

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11
Q

what does cholera toxin do

A

over produces cAMP leading to CFTR to eflux ions (and water) out of cells

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12
Q

What does botulinum toxin do

A

inhibits release of aCH, stopping mm contraction

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13
Q

What does tetanus toxin do

A

motor neurons will be hyperexcitable because inhibatory neurons are stopped.
Shows as highly active mm spasms

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14
Q

What is the effect of endotoxins

A

all show the same s+s

  • fever
  • mm proteolysis
  • uncontrolled intravascular coaulation
  • shock
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15
Q

2 ways in which bacteria cause tissue damaeg

A
  1. Inflammatory rxns due to extra/intracellular multiplication
  2. Tissue damage due to toxins
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16
Q

ways in which fungi cause tissue damage (zymosan)

A

Enzymes and metabolic by products cause tissue damage

zymosan- ligand found on surface of fungi (endotoxic effects)

17
Q

How to parasites cause tissue damage (4)

A
  1. mechanical obstruction
  2. competition for host resources
  3. Proteases (secretion of enzymes)
  4. Immunologic rxns
18
Q

Why do sometimes ppl w antibiotics feel worse right after taking them

A

will kill gram neg bac and they will release endo toxins

19
Q

What is the chain of infection steps (6)

A
  1. infectious agent
  2. resevoir
  3. way out of body
  4. method of transmission
  5. person at risk
  6. way into body
20
Q

What are kochs postilates

A
  1. pathogen must be found in every case of disease
  2. Pathogen can be isolated + grown in pure culture
  3. must cause same disease when put into healthy subject
  4. pathogen can be reisolated from new host
21
Q

limitations to kochs postulates

A
  1. pathogens can be isod from pts not showing symp
  2. Some pathogens cant be cultivated on media
  3. exposure to pathogens dont always cause disease
22
Q

what is a nosocomial infection

A

aquired while in healthcare facilities