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microbiology > chapter 15: host pathogen interactions > Flashcards

chapter 15: host pathogen interactions Flashcards

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Biology 101 flashcards
1
Q

pathogenicity

A

the ability of a pathogen to cause disease

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2
Q

virulence

A

a quantitative measure of pathogenicity

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3
Q

virulence factors

A

the properties (gene products) that enable a microorganism to establish itself on or within a host of a particular species and enhance its potential to cause disease

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4
Q

what are the chain of infection events (for a successful infection) ? **5

A

agent identity, virulence of agent, means of exposure to the agent, dose of agent (number of organisms), susceptibility of host to agent

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5
Q

what is the infectious process?

A

a pathogen must contact a host, enter the host, and survive and multiply within the host to cause disease

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6
Q

all pathogens exhibit a preferred _____ of ____ to establish a disease

A

portal of entry

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7
Q

examples of portals of entry

A

skin, eye, mucosal surfaces (respiratory tract, GI tract, genitourinary tract), parenteral route (barriers are penetrated or injured)

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8
Q

infectious dose 50 (IDsub50) is

A

the number of pathogens that will infect 50% of an experimental group of hosts in a specified time, will vary with a pathogen, handwashing reduces # of pathogens, thus decreasing likelihood of disease due to ID threshold

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9
Q

in order to survive, a pathogen needs…

A

a suitable environment, a source of nutrients (in competition with eukaryotic host cells), a protection from harmful host defense mechanisms

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10
Q

microbial virulence factors…

A

provide the pathogen with mechanisms to out-compete host cells and resit their defenses

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11
Q

virulence is the

A

degree/intensity of pathogenicity

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12
Q

virulence is determined by specific virulence factors:

A

toxins, adhesins, capsules, hydrolytic enzymes

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13
Q

toxins

A

kill or impair the host, defeat immune system

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14
Q

adhesins

A

for cell surface attachment

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15
Q

capsules

A

to prevent phagocytosis

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16
Q

hydrolytic enzymes

A

mediate spreading, destroy molecules of immune system

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17
Q

pathogenicity islands are

A

major virulence factors on large segments on chromosomal or plasmid DNA

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18
Q

major virulence factors on large segments on chromosomal or plasmid DNA do what?

A

increase bacterial virulence, absent in nonpathogenic members, common sequence characteristics (insertion-like sequences for mobility, G+C content different from bacterial genome, several open reading frames, can be spread through horizontal transfer of virulence genes to back)

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19
Q

adhesins and ligands…

A

bind to receptors on host cells

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20
Q

examples of adhesins and ligands (different for different bacteria)

A

glycocalyx, fimbriae, M protein

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21
Q

capsules…

A

prevent phagocytosis by macrophages and neutrophils

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22
Q

different components of cell walls

A

M protein (resistant to phagocytosis), Opa proteins (inhibit T helper cells, Mycolic acid (waxy lipid that resists digestion

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23
Q

enzymes that aid in colonization

A

coagulase, kinases, hyaluronidase, collagenase, IgA proteases

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24
Q

coagulase

A

coagulates fibrinogen

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25
Q

kinases

A

digest fibrin clots

26
Q

hyaluronidase

A

hydrolyzes hyaluronic acid (found in connective tissue)

27
Q

collagenase

A

hydrolyzes collagen

28
Q

IgA proteases

A

destroy IgA antibodies

29
Q

how do pathogens hijack the host cell’s cytoskeleton?

A

invasins

30
Q

invasins

A

Salmonella alters host actin to enter a host cell, use actin to move from one cell to the next

31
Q

how does a pathogen scavenge a host’s nutrients?

A

uses its iron

32
Q

toxin

A

a microbial substance that contributes to pathogenicity by inflicting specific damage on the host

33
Q

toxigenicity

A

ability of bacterium to produce a toxin

34
Q

toxemia

A

presence of toxin in the host’s blood

35
Q

toxoid

A

inactivated toxin used in a vaccine

36
Q

antitoxin

A

antibodies raised against a specific toxin that can be therapeutic

37
Q

intoxications

A

diseases that result from entry of a specific preformed toxin into host, ex: tetanus

38
Q

exotoxins

A

produced inside pathogenic bacteria, most commonly gram + bacteria, as part of their growth and metabolism, exotoxins are then secreted into the surrounding medium during log phase

39
Q

endotoxins

A

lipid portions of lipopolysaccharides that are part of the outer membrane of the cell wall of gram - bacteria, endotoxins are liberated when the bacteria die and the cell wall breaks apart

40
Q

lethal dose 50 (LDsub50)

A

dose of toxin that kills 50% of experiment animals within a specified period of time

41
Q

membrane disrupting toxins lyse host cells by

A

making protein channels in the plasma membrane (leukocidins, hemolysins, streptolysins) and disrupting the phospholipid bilayer

42
Q

what are superantigens

A

cause an intense immune response due to the release of cytokines from host cells, causes sx like fever, nausea, vomiting, diarrhea, shock and death

43
Q

how do superantigens do their thing

A

stimulate about 30% of T cells of the immune system and causes T cells to overexpress and release cytokines, results in the failure of several host organs allowing time for the microbe to disseminate

44
Q

source of exotoxins

A

gram+ and -

45
Q

exotoxin relation to microbe

A

often encoded by lysogenic phage, plasmids, or pathogenicity islands

46
Q

chemistry of exotoxins

A

protein, often enzymes

47
Q

fever with exotoxins

A

no

48
Q

are exotoxins neutralized by antitoxin?

A

yes

49
Q

lethal dose 50 of exotoxins

A

low

50
Q

source of endotoxins

A

gram-

51
Q

endotoxin relation to microbe

A

outer membrane

52
Q

chemistry of endotoxins

A

lipid A

53
Q

fever with endotoxins

A

yes

54
Q

are endotoxins neutralized by antitoxins?

A

no

55
Q

lethal dose 50 of endotoxin

A

relatively large

56
Q

extracellular pathogens

A

grow outside cells in blood, tissue fluids

57
Q

intracellular pathogens

A

grow and multiply within cells, facultative intracellular pathogens (grow within or outside cells), obligate intracellular pathogens (only grow when inside cells)

58
Q

two main factors of host susceptibility

A

defense mechanisms of host (innate and adaptive/acquired immunity) and pathogenicity of pathogen

59
Q

what also plays a role in the host’s susceptibility to infection

A

nutrition, genetic predisposition, and stress

60
Q

what are the different portals of exit?

A

respiratory tract (coughing and sneezing), GI tract (feces and saliva), Genitourinary tract (urine and vaginal secretions), skin, blood (biting arthropods and needles or syringes

microbiology (10 decks)

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