Micb 202: Bacterial Disease Xi - Toxins

Front 1

What are the three main categories of exotoxin?

Back 1

cytolytic toxins
neurotoxins
enterotoxins

Front 2

What are the two types of toxin?

Back 2

endotoxin
exotoxin

Front 3

What do cytolytic toxins do? Give an example.

Back 3

attack cell components causing lysis. Staphylococcus aureus hemolysin lyses red blood cells.

Front 4

What do neurotoxins do? Give an example.

Back 4

interfere with nerve cell function. tetanus toxin.

Front 5

What do enterotoxins do? Give an example.

Back 5

affect cells lining intestinal tract. eg cholera toxin

Front 6

Define exotoxin

Back 6

a secreted protein made by Gram-positive and negative bacteria

Front 7

Are exotoxins immunogenic?

Back 7

yes

Front 8

Are exotoxins heat labile (sensitive)?

Back 8

yes

Front 9

What is the most common endotoxin produced by Gram(-) bacteria?

Back 9

LPS

Front 10

What is the most common endotoxin produced by Gram(+) bacteria?

Back 10

lipoteichoic acid

Front 11

Define endotoxin

Back 11

non-protein toxin molecule

Front 12

Are endotoxins immunogenic?

Back 12

not really

Front 13

___toxins are proteins excreted by bacteria, and are generally heat labile

Back 13

exo

Front 14

___toxins are LPS-lipoprotein complexes released on cell lysis as part of the outer membrane of Gram(-) bacteria

Back 14

endo

Front 15

___toxins are extremely heat stable

Back 15

endo

Front 16

___toxins act specifically

Back 16

exo

Front 17

cytotoxins, enterotoxins, and neurotoxins are all ___toxins

Back 17

exo

Front 18

___toxins are highly toxic, often fatal, whereas ___toxins are weak and rarely fatal

Back 18

exo, endo

Front 19

___toxins are relatively poor immunogens, whereas ___toxins are very good immunogens and stimulate productionf of neutralizing antibodies

Back 19

endo, exo

Front 20

toxoids cannot be made from ___toxins

Back 20

endo

Front 21

treatment of ___toxins with formaldehyde or heat yields a toxoid

Back 21

exo

Front 22

___toxins do not produce fever in host

Back 22

exo

Front 23

___toxins often produce fever in host

Back 23

endo

Front 24

Vibrio cholerae uses a ___toxin to damage its host

Back 24

enterotoxin

Front 25

Describe the Vibrio cholerae morphology

Back 25

motile
Gram(-) curved rod
single, polar flagellum

Front 26

Where can Vibrio cholerae survive?

Back 26

fresh or brackish water
small intestine of humans

Front 27

What is Vibrio cholerae host range?

Back 27

only humans

Front 28

Vibrio cholerae strains are serotyped based on thier ___ antigen

Back 28

LPS O antigen

Front 29

Two serogroups known as __ and __ are responsible for cholera outbreaks

Back 29

O1 and O139

Front 30

Vibrio cholerae has three major virulence factors. What are they?

Back 30

cholera toxin
Tcp pili
flagellum

Front 31

How is cholera spread?

Back 31

fecal contamination of water and food

Front 32

Cholera occurs usually in ___

Back 32

epidemics

Front 33

What are the cholera symptoms?

Back 33

Massive diarrhea (rice water stool containing 10^8 vibrios), resulting in electrolye loss, dehydration, anuria, acidosis, and shock

Front 34

Describe the structure of cholera toxin

Back 34

multimeric protein complex composed of five identical binding (B) subunits and an A (enzymatic) subunit

Front 35

one of the B subunits of CT binds to a ___ receptor, causing the ___ to be cleaved

Back 35

glycolipid. A subunit

Front 36

After cleavage, the A1 portion of the A subunit enters into ___

Back 36

the cytosol of the intestinal epithelial cell

Front 37

___ activates the host cell's adenylate cyclase enzyme, which does what?

Back 37

A1. It converts ATP into cAMP.

Front 38

What does cAMP do?

Back 38

stimulates the secretion of large amounts of Cl ions from cell into lumen of intestine

Front 39

The loss of chlorine ions from intestinal epithelial cells results in what?

Back 39

An electrical gradient that pulls sodium, potassium and other ions from cells, causing new electrolyes to be pulled from blood

Front 40

What is the overall effect of cholera toxin on cells?

Back 40

It turns them into pumps for water and electrolytes

Front 41

How is cholera spread?

Back 41

fecal-oral route

Front 42

Is Vibrio cholerae acid sensitive?

Back 42

yes

Front 43

Why is a large dose of Vibrio cholerae required to produce disease?

Back 43

A lot of the Vibrio cholerae die because of gastric acidity

Front 44

Vibrio cholerae are well adapted to survive in what part of the GI tract?

Back 44

small intestine

Front 45

How does Vibrio cholerae withstant propulsive gut activity?

Back 45

by swimming

Front 46

Vibrio cholerae lacking TCP pili are still pathogenic (T/F)

Back 46

F

Front 47

What does Vibrio cholerae TCP pili do?

Back 47

causes bacteria to aggregate
facilitates adherence to the intestinal mucosa

Front 48

What is the treatment for cholera?

Back 48

rapid replacement of fluids and electrolytes through Gatorade-like solution

Front 49

Describe the current cholera vaccine. What serogroups is it effective against?

Back 49

CVD 103-HgR is an oral, live, attenuated cholera vaccine effective only against O1 serogroup

Front 50

Recurrent infections of cholera are rare (T/F). Why?

Back 50

T. Antibodies are developed during first infection.