B2.081 Bacterial Toxins and Dehydration

Question 1

what are the 4 classes of bacterial toxins?

Answer 1

1. surface acting
2. membrane damaging
   - hydrolysis of membrane lipids
   - formation of pores
3. intracellular acting
4. injected toxins

Question 2

what is the heat labile (LT) mechanism?

Answer 2

AB toxin
specific to intestinal epithelial cells
hijacks internal cell signaling mechanism to activate CFTR
increases excretion of chloride ions

Question 3

what is the heat stable (ST) mechanism?

Answer 3

surface acting toxin
specific for intestinal epithelial cells
binds cell surface signaling molecules
increases diverse ion pump functions

Question 4

what provides the stability in ST toxins?

Answer 4

2 disulfide bonds

Question 5

what is the mechanism of the shiga toxin?

Answer 5

AB toxin
causes cessation of RNA translation and protein synthesis
activates platelet aggregation (HUS)

Question 6

what happens in the endosome after the engulfment of a toxin?

Answer 6

acidified by proton pump
drop in pH triggers conformational change in a subunit
globular>integral

Question 7

what is the mechanism of diphtheria toxin?

Answer 7

binds to membrane bound receptors and enters via receptor-mediated endocytosis
after acidification, A domain is inserted into cytosol
A collects and inhibits protein synthesis by ribosylating EF-2

Question 8

what are the hallmarks of anthrax?

Answer 8

painless lesions
lymph node swelling
livestock

Question 9

what is the anthrax mechanism?

Answer 9

PA protein forms pore in membrane
LF and EF brought into cell via endosome
lowered pH triggers conformational change
pore allows lethal proteins access to cytosol

Question 10

how can you tell if you ingested a preformed toxin?

Answer 10

symptoms arise in less than 3 hours

Question 11

what is the duration of diarrhea when only the toxin was ingested?

Answer 11

shorter than usual

24-48 hours

Question 12

what type of protein is the botulism toxin (BoNT)?

Answer 12

peripheral

interacts with GD1a (ganglioside) and Syt II/SV2

Question 13

what differs in the receptors for BoNT and TeNT?

Answer 13

only one sugar unit on the sphingosine derived phospholipid

changes import mechanism

Question 14

how do the effects of BoNT and TeNT differ?

Answer 14

BoNT blocks acetylcholine release of the PNS

TeNT is retoaxonally transported to intraneurons of the CNS

Question 15

what is the mechanism of the C.diff toxin?

Answer 15

AB toxin
A disrupts ion pump
B damages actin

Question 16

what is pseudomembrane colitis?

Answer 16

bacterial aggregation on colonic mucosa

Question 17

what is the result of the C.diff toxin?

Answer 17

enterocyte destruction
loss of membrane integrity
loss of fluid control

Question 18

what is the result of pseudomembrane colitis?

Answer 18

inflammatory reaction that causes necrosis of the mucosal layer and decreased fluid absorption

Question 19

what toxin is associated with campylobacter jejuni?

Answer 19

cytolethal distending toxin

AB toxin

Question 20

what is the mechanism of the cytolethal distending toxin?

Answer 20

arrests cell cycle at G2/M phase

results in mucosal cell destruction and inflammatory necrosis (bloody) with loss of fluid control

Question 21

what is the benefit of using a T3SS?

Answer 21

injection of toxins directly into cells through a pore

bypasses barrier mechanisms or need for membrane transporters

Question 22

what channels transport water?

Answer 22

aquaporins

Question 23

when are antibiotics appropriate to treat ETEC associated diarrhea?

Answer 23

> 5 days