6. Virulence Factors

Question 1

define virulence

Answer 1

refers to the degree of damage caused by a microbe to its host

Question 2

what do adhesins bind to

Answer 2

sugar residues in host receptors

Question 3

what do the pili of neisseria gonorrhoea bind to

Answer 3

galactose

Question 4

what do the fimbriae of Escherichia coli bind to

Answer 4

mannose

Question 5

what do flagella (adhesin) bind to

Answer 5

toll-like receptor 5

this is not a glycoprotein

Question 6

adhesins provide initial attachment, what follows this?

Answer 6

docking with membrane adhesin proteins

Question 7

what do membrane adhesin proteins bind to

Answer 7

collagen, fibronectin & laminin

Question 8

what virulence factors ARE quorum-sensing controlled

Answer 8

capsule
invasions
exotoxins

Question 9

what virulence factors ARE NOT quorum-sensing controlled

Answer 9

adhesins
endotoxins
siderosphores

Question 10

briefly describe the capsule

Answer 10

polysaccharide layer (mainly composed of alginate), lies outside the cell envelope

involved in attachment, protection from antimicrobials

Question 11

what do invasins do

Answer 11

act to break down host cells in the immediate vicinity of bacterial growth

Question 12

what enzymes do invasion’s use to penetrate through epithelium cells

Answer 12

hyaluronidase, neuraminidase, collagenase, coagulase

Question 13

what produces hyaluronidase

Answer 13

Gram-positives

Question 14

name two Gram-positive bacteria

Answer 14

streptococci, staphylococci

Question 15

what does hyaluronidase do

Answer 15

attacks interstitial cement of connective tissues by depolymerising hyaluronic acid

Question 16

what does collagenase target? how? what produces it?

Answer 16

muscles
breaks down collagen
clostridium

Question 17

what has longer range: invasins or toxins

Answer 17

toxins - these can be spread around the body

Question 18

what are endotoxins? when does it become toxic?

Answer 18

the lipopolysaccharide found in the walls of gram negative bacteria, it becomes toxic when the cell wall is damaged and lipid A leaks from the cell wall

Question 19

once in its toxic state, what effects do lipid A have

Answer 19

• causes host cels to release endogenous pyrogens which target the hypothalamus
• this activates many host systems that cause damage

Question 20

what is the problem with endotoxins in the pharmaceutical industry

what is the solution?

Answer 20

drugs are filtered for Gram-ve bacteria which can cause lysis = lipid A leakage.

• must be carbon filtered once again to remove endotoxin traces

Question 21

what bacteria produce exotoxins

Answer 21

both gram+ and gram-ve

Question 22

name 3 types of exotoxins

Answer 22

cytolytic toxins
A-B toxins
superantigens

Question 23

describe cytolytic toxins mechanism of action

Answer 23

insert a pore into the membrane or producing enzymes to attack phospholipids

Question 24

staph aureus Alpha toxin is a cytolytic toxin, how does it work

Answer 24

inserts itself into the host membrane, allowing cell contents to flow out of its pore

Question 25

describe the structure of A-B toxins

Answer 25

one A subunit and 5 B subunits

Question 26

how do A-B toxins use

Answer 26

the B subunit binds to the outside of the cell to get the A subunit into the cell (A subunit interferes with protein synthesis)

Question 27

what do B subunits in A-B toxins bind to

Answer 27

glycans

Question 28

give an example of a A-B toxin, how does it work

Answer 28

botulinum neurotoxin

binds to glycans on the pre-synaptic membrane - causing paralysis

Question 29

superantigens are another form of exotoxin, what do they do

Answer 29

stimulate large numbers of t-cells and subsequent cytokines = severe inflammation, shock, organ failure

Question 30

how do siderophores work

Answer 30

confiscate iron from host cells (e.g. transferrin), for it to be taken up by bacterial cells

Question 31

describe the mode of action of the gastroenteritis toxin

Answer 31

• toxin is endocytose into the cell where it is transported to the ER via phagosome
• causes cAMP to rise and cause electrolyte imbalance
• water leaves the cell causing dehydration and diarrhoea

Question 32

what do cytokines activate

Answer 32

activate macrophages = inflammation

Question 33

what happens in toxic shock syndrome

Answer 33

staph. aureus toxin 1 causes secretion of fluids and electrolytes = reduced bp and blood volume

Question 34

by what two ways can we be exposed to toxins

Answer 34

1. intoxication -> taking in a preformed toxin

2. colonisation of a surface - once quorum is reached- toxins are produced

Question 35

how does clostridium botulinum toxin enter the body

Answer 35

ingested into the body - pre-formed toxin found in food