Microbial Mechanisms of Pathogenicity

Question 1

Define pathogens

Answer 1

Disease causing microorganism

Question 2

Define pathogenicity

Answer 2

ability to cause disease

Question 3

Define virulence

Answer 3

degree of pathogenicity

Question 4

Define infection

Answer 4

when body is invaded by a harmful microorganism

Question 5

Define disease

Answer 5

when the health of the human body is affected by an infection

Question 6

What are 3 portals of entry

Answer 6

1) mucous membrane
2) skin
3) parenteral route

Question 7

What us the easiest and most common entry

Answer 7

respiratory tract ( mucous membrane)

Question 8

Define ID50

Answer 8

infectious dose for 50% of a sample population

measures virulence of a microbes

Question 9

Define LD50

Answer 9

lethal dose for 50% of a sample population

measures potency of a toxin

Question 10

What are 2 ways of adherence of microorganisms to Host cells

Answer 10

1) Surface molecules on the pathogens

2) bind to complementary surface receptors of host cell

Question 11

Describe surface molecules on the pathogens

Answer 11

adhesins or ligands
located on glycocalyx or fimbraie or pili
glycoproteins or lipoproteins

Question 12

Define bind to compementary surface receptors of host cell

Answer 12

mannose-sugar

Question 13

What are 4 ways pathogens pentrate host defenses

Answer 13

1) capsules
2) cell wall components
3) enzymes
4) antigenic variation

Question 14

Describe capsules as a way to penetrate host defenses

Answer 14

glycocalyx around the cell wall
impair phagocytosis ( streptococcus pneumoniae, haemophilus influenza,bacillus anthracis)
have capsule increased virulence
body can create antibodies against capsules

Question 15

Describe cell wall components to penetrate host defenses

Answer 15

1) M protein resists phagocytosis
2) Opa protein
3) waxy lipid ( mycolic acid) resists digestion

Question 16

Describe how M protein resists phagocytosis

Answer 16

streptococcus pyogenes

produce heat resistence and resistent proteins

Question 17

Describe Opa protein as away to penetrates host defenses

Answer 17

Neisseria gohorrhoeae
attach to host cell
use fimbrae and outer membrane protein
inhibit T helper cell

Question 18

Describe waxy lipid as a wayof penetrating host defenses

Answer 18

resists digestion
ex: mycobacterium tuberculosis
has ability to divide in microphage

Question 19

What are 5 enzymes used to penetrate host defenses

Answer 19

1) Coagulases
2) Kinases
3) Hyaluronidase
4) Collagenase
5) IgA proteases

Question 20

Describe the enzyme coagulases

Answer 20

coagulate fibrinogen
helps with formation of clot. so when infection bacteria form a blood clot,form a wall, and prevent bloodflow to infection site so immune system cells can’t get to site
ex. staphylococcus

Question 21

Describe kinases as a way to penetrate host defenses

Answer 21

digest fibrin clots
bacteria will destroy the clotthat host body creates to defend itself so that infection can spread
ex. streptococcous

Question 22

Describe hyaluronidase as a way to penetrate host defenses

Answer 22

digests polysaccharides that hold cells together
produced by streptococcus
ex.gasgrene

Question 23

Describe collagenase as a enzyme to penetrate host defenses

Answer 23

breaks down collagen

Question 24

Describe IgA proteases as a way to penetrate host defenses

Answer 24

destroy IgA antibodies

Question 25

Describe antigenic variation as a way of penetrate hoat defenses

Answer 25

pathogens alter their surface antigens
evade destruction by host antibodies
ex. neisseria,influenza virus

Question 26

Describe invasins as a way to penetrate into host cell cytoskeleton

Answer 26

surface proteins produced by bacteria
rearrange actin filaments of the cytoskeleton
cause membrane ruffling
ex. salmonella typhi
use actin to move from 1 cell to the next ( shigella and listeria)

Question 27

What are 3 ways that bacterial pathogens damage host cells

Answer 27

1) by using the host’s nutrients
2) direct damage
3) production of toxins

Question 28

How do using host’s nutrients a way bacterial pathogens damage host cells ( example of one way is the answer)

Answer 28

siderophores-proteins secreted by pathogens
binds iron more tightly than host cells
siderophores has higher affinity for iron then hemoglobin

Question 29

Describe 4 direct damage as a bacterial pathogens damage host cell

Answer 29

disrupts host cell function
uses host cell nutrients
produces waste products
multiples in host cells and cause ruptures

Question 30

Define toxins

Answer 30

poisonous substance produced by microorganisms

produce fever,cardiovascular problem,diarrhea,shock

Question 31

Define toxigenicity

Answer 31

ability of a microorganism to produce a toxin

Question 32

Describe toxemia

Answer 32

presence of toxin in the host’s blood

Question 33

What are the 2 types of toxins

Answer 33

exotoxins

endotoxins

Question 34

Describe exotoxins

Answer 34

proteins produced and secreted by bacteria
soluble in body fluids,destroy host cells and inhibit metabolic functions
ex. hemolysins ( released by beta hemolytic streptococci)
ex. botulinum toxin ( neurotoxin, release by clostridium botulinum)
ex. tetanus toxin ( neurotoxin) released by clostridium tetanu

Question 35

Exotoxins
Sources?
Relation to microbe?
Chemistry?
Fever?
Neutralized by antitoxin?
LD50

Answer 35

mostly gram +
by-products of growing cell
protein
no 
yes
small

Question 36

Describe enterotoxins

Answer 36

exotoxins whose activity affects the small intestine
cause are massive secretion of fluid into intestinal lumen and vomiting and diarrhea
ex. vibrio enterotoxin and shiga toxin

Question 37

Describe endotoxins
bacteria type?
2 examples of bacteria that have this toxin?

Answer 37

Lipid A portion of lipopolysaccharides ( LPS) OF GRAM NEGATIVE BACTERIA
released when the bacteria die
ex. salmonella typhi and proteus vulgaris

Question 38

Endotoxin
Source
relation to microbes
chemistry
fever
neutralized by antitoxin
ld50

Answer 38

gram -
outer membrane
lipid A
yes
no
relatively large

Question 39

Describe 5 portals of exit

Answer 39

1) Respiratory tract
2) gastrointestinal tract
3) genitourinary tract
4) skin
5) blood