chapter 15: host pathogen interactions

Question 1

pathogenicity

Answer 1

the ability of a pathogen to cause disease

Question 2

virulence

Answer 2

a quantitative measure of pathogenicity

Question 3

virulence factors

Answer 3

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

Question 4

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

Answer 4

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

Question 5

what is the infectious process?

Answer 5

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

Question 6

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

Answer 6

portal of entry

Question 7

examples of portals of entry

Answer 7

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

Question 8

infectious dose 50 (IDsub50) is

Answer 8

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

Question 9

in order to survive, a pathogen needs…

Answer 9

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

Question 10

microbial virulence factors…

Answer 10

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

Question 11

virulence is the

Answer 11

degree/intensity of pathogenicity

Question 12

virulence is determined by specific virulence factors:

Answer 12

toxins, adhesins, capsules, hydrolytic enzymes

Question 13

toxins

Answer 13

kill or impair the host, defeat immune system

Question 14

adhesins

Answer 14

for cell surface attachment

Question 15

capsules

Answer 15

to prevent phagocytosis

Question 16

hydrolytic enzymes

Answer 16

mediate spreading, destroy molecules of immune system

Question 17

pathogenicity islands are

Answer 17

major virulence factors on large segments on chromosomal or plasmid DNA

Question 18

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

Answer 18

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)

Question 19

adhesins and ligands…

Answer 19

bind to receptors on host cells

Question 20

examples of adhesins and ligands (different for different bacteria)

Answer 20

glycocalyx, fimbriae, M protein

Question 21

capsules…

Answer 21

prevent phagocytosis by macrophages and neutrophils

Question 22

different components of cell walls

Answer 22

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

Question 23

enzymes that aid in colonization

Answer 23

coagulase, kinases, hyaluronidase, collagenase, IgA proteases

Question 24

coagulase

Answer 24

coagulates fibrinogen

Question 25

kinases

Answer 25

digest fibrin clots

Question 26

hyaluronidase

Answer 26

hydrolyzes hyaluronic acid (found in connective tissue)

Question 27

collagenase

Answer 27

hydrolyzes collagen

Question 28

IgA proteases

Answer 28

destroy IgA antibodies

Question 29

how do pathogens hijack the host cell's cytoskeleton?

Answer 29

invasins

Question 30

invasins

Answer 30

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

Question 31

how does a pathogen scavenge a host's nutrients?

Answer 31

uses its iron

Question 32

toxin

Answer 32

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

Question 33

toxigenicity

Answer 33

ability of bacterium to produce a toxin

Question 34

toxemia

Answer 34

presence of toxin in the host's blood

Question 35

toxoid

Answer 35

inactivated toxin used in a vaccine

Question 36

antitoxin

Answer 36

antibodies raised against a specific toxin that can be therapeutic

Question 37

intoxications

Answer 37

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

Question 38

exotoxins

Answer 38

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

Question 39

endotoxins

Answer 39

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

Question 40

lethal dose 50 (LDsub50)

Answer 40

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

Question 41

membrane disrupting toxins lyse host cells by

Answer 41

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

Question 42

what are superantigens

Answer 42

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

Question 43

how do superantigens do their thing

Answer 43

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

Question 44

source of exotoxins

Answer 44

gram+ and -

Question 45

exotoxin relation to microbe

Answer 45

often encoded by lysogenic phage, plasmids, or pathogenicity islands

Question 46

chemistry of exotoxins

Answer 46

protein, often enzymes

Question 47

fever with exotoxins

Answer 47

no

Question 48

are exotoxins neutralized by antitoxin?

Answer 48

yes

Question 49

lethal dose 50 of exotoxins

Answer 49

low

Question 50

source of endotoxins

Answer 50

gram-

Question 51

endotoxin relation to microbe

Answer 51

outer membrane

Question 52

chemistry of endotoxins

Answer 52

lipid A

Question 53

fever with endotoxins

Answer 53

yes

Question 54

are endotoxins neutralized by antitoxins?

Answer 54

no

Question 55

lethal dose 50 of endotoxin

Answer 55

relatively large

Question 56

extracellular pathogens

Answer 56

grow outside cells in blood, tissue fluids

Question 57

intracellular pathogens

Answer 57

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

Question 58

two main factors of host susceptibility

Answer 58

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

Question 59

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

Answer 59

nutrition, genetic predisposition, and stress

Question 60

what are the different portals of exit?

Answer 60

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