Lecture 10 - exotoxins & endotoxins

Question 1

3 types of exotoxins

Answer 1

enterotoxins
cytotoxins
neurotoxins

Question 2

where do enterotoxins work

Answer 2

in intestinal mucosa
so disrupts the GI tract
lots of diarrohoea god how tf do u spell that
e.g. vibrio cholerae

Question 3

where do cytotoxins work

Answer 3

general tissues
typically kill cells viz enzymatic attack

Question 4

how do memb disrupting cytotoxins work

Answer 4

bind to cholesterol in the membranes
forms pores in memb
specifically in RBC
causes beta haemolysis
can be seen on agar plate as zones of clearance

Question 5

how do phsopholipase enzymes attack the membrane

Answer 5

removes charged head group on lipid in memb
cell dies

Question 6

clostridium perfringens (gas gangrene) - mechanism of its major toxin including what it kills

Answer 6

alpha toxin
= a phospholipase
causes lysis of endothelial cells, RBC, WBC, platelets

Question 7

how do the toxins in gas gangrene allow bacteria to grow

Answer 7

since the toxins cut off the supply of O2 to the area but destroying all the cells
the bacterial spores can germinate

Question 8

what type of toxin is bitulinum toxin

Answer 8

neurotoxin
= the most potent poison known

Question 9

what is A-B toxin

Answer 9

just decreibes the heavy and light chain
B typically is the bit that binds to cells
and A will do the toxic stuff

Question 10

what is the heavy and light chain of A-B connected by

Answer 10

disulphide bond

Question 11

how does botulinum toxin cause flaccid paralysis

Answer 11

the light chain = zinc metalloprotease
inhibits release of ACh
prevents muscle contracction

Question 12

how does botulinum toxin cause respiratory paralysis

Answer 12

via food poisioning
usually in canned foods

Question 13

how does botulinum toxin cause floppy baby syndrom

Answer 13

bact transmitted via honey
bact end up making spores in baby’s gut

Question 14

2 treatments that have come from botulinum toxin

Answer 14

botox
treating overactive muscles

Question 15

what type of toxin is vibrio cholerae

Answer 15

enterotoxin
A-B type

Question 16

how many subunits do A and B have respectivelu

Answer 16

A is 1 moleucle only
B has 5 subunits

Question 17

how does cholerae do what it do

Answer 17

the A toxin activates adenylate cyclase = increase ATP breakdown
blocks Na+ movement idek why
CFTR also phsophorylated = Cl- moves to lumen
overall water movement goes to lumen = not good

Question 18

where are endotoxins

Answer 18

on outer memb of gram-ve bacter
in lipopolysachharide memb

Question 19

what part of lipopolysachharide is the endotoxin specifically

Answer 19

lipid A

Question 20

what are the 3 key effects of lipid A

Answer 20

activates monocytes = fever
activates complement cascade = inc permeability of blood vessels by destrouing endothelial lining = dec blood pressure
activates coagulation cascade = vascular coaggulation

Question 21

what determines the toxicity of lipid A

Answer 21

low = less fatty acids and shorter
high = longer fatty acid chain

Question 22

how can lipid A cause systemic effects

Answer 22

vesicles with lipid A in it bleb off bacteria into the tissues and blood

Question 23

why can antibiotic treatment be dangerous for lipid A bacteria

Answer 23

cell wall broken, cells die and release lots of lipid A
= TOXIC SHOCK