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BMSC 210 > Chapter 25 - Bacterial Mechanisms of Pathogenicity > Flashcards

Chapter 25 - Bacterial Mechanisms of Pathogenicity Flashcards

1
Q

pathogenesis

A

how pathogens cause disease

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2
Q

Where Koch’s postulates do not fit

A
  • some pathogens found in healthy people

- all healthy test subject equally susceptible to disease but may not have the same signs and symptoms

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3
Q

pathogens

A

microbial parasites

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4
Q

pathogenicity

A

the ability of a parasite to inflict damage on the host

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5
Q

virulence

A

measure of pathogenicity; relative ability of a pathogen to cause disease

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6
Q

opportunistic pathogen

A

causes disease only in the absence of normal host resistance

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7
Q

infection

A

situation in which a microorganism is established and growing in a hot, whether or not the host is harmed

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8
Q

disease

A

damage or injury to the host that impairs host function

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9
Q

How can virulence be measured?

A

-from experimental studies of LD50

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10
Q

LD50

A
  • lethal dose 50

- the amount of an agent that kills 50% of the animals in a test group

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11
Q

Highly virulent pathogens show _______________ in the number of cells required to kill 100% of the population as compared to 50% of the population

A

little difference

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12
Q

toxicity

A

organisms produces a toxin that inhibits host cell function or kills host cells

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13
Q

invasiveness

A

ability of a pathogen to grow in host tissue at densities that inhibit host function
-can cause damage without producing a toxin

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14
Q

attenuation

A

decrease or loss of virulence (measles, mumps, rubella, rabies vaccine)

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15
Q

Step One in Pathogenesis: Adherence

A

-bacteria and viruses adhere specifically yo epithelial cells through macromolecular interactions on the surfaces of the pathogen and host cell

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16
Q

How is bacterial adherence facilitated?

A
  • slime layer, capsule

- fimbriae, pili

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17
Q

Step 2 - Invasion

A

pathogens produce various virulence factors that enhance invasiveness
-enzymes, coagulants

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18
Q

Step 3 - Colonization and Infection

A

pathogens may grow locally at the site of invasion or spread throughout the body; availability of nutrients is most important in affecting pathogen growth

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19
Q

bacteremia

A

presence of bacteria in the bloodstream

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20
Q

septicemia

A

bloodborne systemic infection

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21
Q

Genes that direct invasion are clustered together on the chromosome as…

A

pathogenicity islands

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22
Q

SPI1

A

encodes proteins promoting invasion forming an injectisome type III secretion system

23
Q

SPI2

A

genes that promote a more systemic disease

24
Q

exotoxins

A

toxic proteins released from the pathogen as it grows

25
Q

3 categories of exotoxins

A

cytolytic, AB, superaktigen

26
Q

toxicity

A

ability of microorganism to cause disease as a result of a preformed toxin that inhibits host function or kills host cells

27
Q

coagulase (E)

A

a toxin found in staph that induces fibrin clotting

28
Q

streptokinase (E)

A

toxin found in strep that dissolves fibrin clots

29
Q

hyaluronidase (E)

A

toxin found in strep that dissolves hyaluronic acid (glue that cements cells together) in connective tissue

30
Q

injectisome

A

toxin found in salmonella that injects toxins into host cells

31
Q

4 classes of exoenzymes

A

glycohydrolases, nucleases, phospholipase, proteases

32
Q

glycohydrolases

A

degrades hyaluronic acid that cements cells together to promote spreading through tissues
-hyaluronidase

33
Q

nucleases

A

degrades DNA released by dying cells (bacteria and host cells) that can trap the bacteria, thus promoting spread
-DNAse

34
Q

phospholipases

A

degrades phospholipid bilayers of host cells, causing cellular lysis, and degrade membrane of phagosomes to enable escape into the cytoplasm
-phospholipase C

35
Q

proteases

A

degrades collagen in connective tissue to promote spread

-collagenase

36
Q

2 types of superantigens

A
  • toxic shock syndrome toxins
  • streptococcal mitogenic exotoxin
  • streptococcal pyrogenic toxin
37
Q

superantigens

A

stimulates excessive activation of immune system cells and release of cytokines from immune system cells
-results in life-threatening fever, inflammation, and shock

38
Q

cytolytic toxins (cytotoxins)

A

work by degrading cytoplasmic membrane integrity, causing cell lysis and death

39
Q

hemolysins

A

toxins that lyse RBCs

40
Q

staphylococcal a-toxin

A

kills nucleated cells and lyses erythrocytes
-7 subunit pore which causes influx of extracellular components into the cell and efflux of cytoplasmic components out of the cells

41
Q

membrane disrupting toxins

A
  • streptolysin
  • pneumolysin
  • alpha-toxin (staph and clostridium)
  • phospholipase C
  • beta-toxin
42
Q

3 types of membrane disrupting toxin that assemble into pores in cell membranes, disrupting them and killing the cell

A

streptomycin, pneumolysin, a-toxin

43
Q

membrane disrupting toxin phospholipase that degrade cell membrane phospholipids, disrupting function and killing cell

A

a-toxin, phospholipase C, b-toxin

44
Q

AB exotoxins

A

consists of two subunits (A and B)

-work by binding to host cell receptor (B) and transferring damaging agent (A) across the cell membrane

45
Q

examples of AB exotoxins

A

dipththeriae toxin, tetanus toxin, botulinum toxin

46
Q

4 types of intracellular targeting toxins

A

cholera toxin, tetanus toxin, botulinum toxin, diphtheria toxin

47
Q

cholera toxin

A

activation of adenylate cyclase in intestinal cells, causing increased levels of cAMP and secretion of lfuids and electrolytes out of cell, causing diarrhea

48
Q

tetanus toxin

A

inhibits release of inhibitory neurotransmitters in CNS, causing spastic paralysis

49
Q

botulinum toxin

A

inhibit release of acetylcholine from neurons, resulting in flaccid paralysis

50
Q

diphtheria toxin

A

inhibition of protein synthesis, causing cellular death

51
Q

enterotoxins

A
  • AB toxin
  • affects small intestine
  • cause massive secretion of fluid into intestinal lumen, resulting in vomiting and diarrhea
  • less toxic than exotoxins
52
Q

lipopolysaccharide

A

portion of cell envelope of certain gram-neg bacteria which is a toxin when solubilized

53
Q

limulus amoebocyte lysate (LAL) assay

A

can detect presence of endotoxins

BMSC 210 (15 decks)

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