Ch 15 Mechanisms of Pathogenicity

Question 1

what is a microbes ID50?

Answer 1

number of microbes needed when presented to a population to infect 50% w the disease. (ID= infectious dose)

Question 2

is a higher or lower ID50 better?

Answer 2

higher- more microbes needed to cause disease

Question 3

what is a microbes LD50?

Answer 3

concentration of toxin needed to cause 50% of test population to die (LD= lethal dose)

Question 4

3 portals of microbial entry and examples

Answer 4

1. MM- resp. tract, GI tract, conjun., genitourinary tract
2. skin- openings like sweat glands and hair follicles (acne)
3. parenteral- damage due to cuts, insect bites, drying out of skin (cracking)

Question 5

what is adherence of a microbe

Answer 5

latching on to particular receptors on cell surface of host via ligands/adhesins

Question 6

examples of enzymes used by pathogens to escape host defenses

Answer 6

coagulase- clots blood creating a barrier from IS

kinase- blocks formation of clots, once a certain number of pathogens is reached, kinase used to launch attack

Question 7

theraputic application of kinase

Answer 7

streptokinase used to break up blood clots that cause heart attacks

Question 8

how antigenic variation is used to escape host defenses

Answer 8

ability of microbes to change its surface antigens, ecading antibodies

Question 9

what are siderophores, how damage host cells?

Answer 9

protein secreted by some pathogens, have high affinity for iron, take iron (ex: from hemoglobin RBCs), pathogen will take-up iron for growth and reproduction

Question 10

exo v endo toxins- gram neg or pos?

Answer 10

exo- pos

endo- neg

Question 11

difference between endo and exo toxins (where they are)

Answer 11

endo- w/in outer membrane

exo- secreted by growing cell

Question 12

what component of gram neg cell acts as endo toxin

Answer 12

lipid A

Question 13

which usually has a lower LD, exo or endo toxins

Answer 13

exo (less needed to be deadly)

Question 14

which causes fever, endo or exo toxins

Answer 14

endo toxins- lipid A released in macrophage-> produces cytokines->bloodstream-> hypothalamus-> make porstaglandin-> changes thermostat

Question 15

why, if someone has a gram ned infection, we are not TOO aggressive w treatment

Answer 15

killing all at once releases endotoxins all at once-> bad fever

Question 16

how A-B toxins work

Answer 16

1. B component attaches to host cell receptor
2. host cell invaginates A-B (receptor-mediated endocytosis)
3. A part separates, disrutes cellular metabolism and prevents protein synthesis

Question 17

why the A part of A-B toxin acts as an enzyme (what does that mean?)

Answer 17

repeated and continuous disruptive effect

Question 18

how a virus can cause cancer?

Answer 18

insert into host genome leading to mutations and cancer.

can also decrease contact inhibition- stop knowing that, when they bump into each other, stop growing-> tumors

Question 19

Bacterial enzyme associated w blackening of infected wounds, how does this aid in pathogenicity?

Answer 19

Hyalauronidase, helps microorganisms spread from initial site of infection (hydrolyzes hylaronic Acid)

Question 20

How exotoxins are produced

Answer 20

Part of cells growth and metabolism

Question 21

How exotoxins harm host

Answer 21

Inhibiting certain metabolic functions or destroying parts of host cell

Question 22

A-B is a kinda of endo or exotoxins?

Answer 22

Exo