B2.081 Bacterial Toxins and Dehydration Flashcards Preview

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Flashcards in B2.081 Bacterial Toxins and Dehydration Deck (23)
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1

what are the 4 classes of bacterial toxins?

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

2

what is the heat labile (LT) mechanism?

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

3

what is the heat stable (ST) mechanism?

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

4

what provides the stability in ST toxins?

2 disulfide bonds

5

what is the mechanism of the shiga toxin?

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

6

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

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

7

what is the mechanism of diphtheria toxin?

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

8

what are the hallmarks of anthrax?

painless lesions
lymph node swelling
livestock

9

what is the anthrax mechanism?

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

10

how can you tell if you ingested a preformed toxin?

symptoms arise in less than 3 hours

11

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

shorter than usual
24-48 hours

12

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

peripheral
interacts with GD1a (ganglioside) and Syt II/SV2

13

what differs in the receptors for BoNT and TeNT?

only one sugar unit on the sphingosine derived phospholipid
changes import mechanism

14

how do the effects of BoNT and TeNT differ?

BoNT blocks acetylcholine release of the PNS
TeNT is retoaxonally transported to intraneurons of the CNS

15

what is the mechanism of the C.diff toxin?

AB toxin
A disrupts ion pump
B damages actin

16

what is pseudomembrane colitis?

bacterial aggregation on colonic mucosa

17

what is the result of the C.diff toxin?

enterocyte destruction
loss of membrane integrity
loss of fluid control

18

what is the result of pseudomembrane colitis?

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

19

what toxin is associated with campylobacter jejuni?

cytolethal distending toxin
AB toxin

20

what is the mechanism of the cytolethal distending toxin?

arrests cell cycle at G2/M phase
results in mucosal cell destruction and inflammatory necrosis (bloody) with loss of fluid control

21

what is the benefit of using a T3SS?

injection of toxins directly into cells through a pore
bypasses barrier mechanisms or need for membrane transporters

22

what channels transport water?

aquaporins

23

when are antibiotics appropriate to treat ETEC associated diarrhea?

>5 days