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Medical Microbiology > Lecture 12: Bacterial Exotoxins > Flashcards

Lecture 12: Bacterial Exotoxins Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

True or False: Exotoxins are nucleic acids

A

False - proteins

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2
Q

True or False: Exotoxins are found in gram negative and positive bacteria and can be detected at human/animal/insect cells

A

True

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3
Q

True or False: Exotoxins can be made into effective vaccines and treat conditions like CP

A

True

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4
Q

True or False: Exotoxin is important for survival and propagation of bacterium that produce them

A

True

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5
Q

Where are the toxin genes commonly carried on?
1.
2.

A

1) Plasmids and 2) Lysogenic bacteriophages - e.g Diptheria

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6
Q

True or False: Some exotoxins are not excreted. Rather, they accumulate inside cell and are released by cell lysis.

A

True

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7
Q

____: a specific term that denotes exotoxins released by bacteria in intestines, which can cause diarrhea or vomiting

A

Enterotoxin

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8
Q

___ is embedded in bacterial surface and released when bacteria lysis

A

LPS (endotoxin)

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9
Q

What are the three types of toxins?

A
  1. Type 1 (Superantigen toxins/surface acting)
  2. Type II (Membrane-Disrupting Toxins)
  3. Type III Toxins (A-B Toxins)
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10
Q

Type ___ Toxins bind to host cell surface but is not translocated into host cell. Further, it allows for binding to MHC Class II and receptor on T cells that interact with MHC.

A

Type I

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11
Q

Many ___ cells can be stimulated by bridging action of superantigens
A. B cells
B. T cells
C. Macrophages

A

B. T cells

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12
Q

What symptoms arise as a result of Type I toxins?

A

Nausea, vomit, malaise, fever (toxic shock syndrome)

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13
Q

Three examples of type 1 toxins?

A
  1. TSST (S. aureus)
  2. Streptococcal
  3. Enterotoxin (E. coli)
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14
Q

Which toxin lysis the host cell by disrupting integrity of their cytoplasmic membranes?
A. Type 1
B. Type 2
C. Type 3

A

B. Type 2

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15
Q

What are the two different types of Type 2 (Membrane Disrupting) Toxins?

A
  1. Pore forming cytotoxins
  2. Enzyme cytotoxins
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16
Q

The primary role of Type II toxins is to kill host cells, particularly ____

A

phagocytes

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17
Q

S. aureus alpha-hemolysin is an example of which bacterial exotoxin?
A. Type 1
B. Type 2
C. Type 3

A

B. Type 2 - pore

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18
Q

Invasive bacteria use Type __ exotoxins to escape from phagosome and enter host cell cytoplasm

A. Type 1
B. Type 2
C. Type 3

A

B. Type 2

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19
Q

_____ cytotoxins insert into host cell membrane and make open channel (pore), which triggers a sudden inrush of water. This causes cell to swell and rupture.
A. Enzyme cytotoxin
B. Pore-forming cytotoxin

A

B. Pore-forming cytotoxin

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20
Q

Which Type II toxin destabilizes host cell membranes by either 1) removing charged head group of lipid portion or 2) cleave at other sites on the phospholipid
A. Enzyme cytotoxin
B. Pore-forming cytotoxin

A

A. Enzyme cytotoxin

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21
Q

Phospholipase, hemolysin, and cytotoxin are examples of which type of Type II toxin?

A. Pore-forming exotoxin
B. Enzyme cytotoxins

A

B. Enzyme cytotoxins

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22
Q

True or False: Type III (A-B Toxins) Toxins are extracellular acting

A

False - intracellular

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23
Q

In Type III Exotoxins, the A subunit is the active, ___ light chain while the B subunit is the heavy chain and is responsible for __

A

enzymatic; binding

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24
Q

True or False: In both simple and complex Type III Exotoxins, the B portion binds to a specific host cell receptor, then translocation regions moves A portion into host cell cytoplasm (either via : endocytosis or directly)

A

True

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25
Q

The compound AB toxin has a B portion made up of __ subunits and __ A subunit

A. one; multiple
B. multiple; one

A

B. multiple; one

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26
Q

When does the A subunit of AB Toxin become enzymatically active and exert its toxic effects?

A

Once A Portion is in the cytoplasm

27
Q

True or False: The A portion of A-B Toxins may enter very different cell types and will likely catalyze DIFFERENT reactions

A

False - the A portion of A-B Toxins may enter very different cell types, but most of them catalyze the SAME reaction (removal of the ADP-ribosyl group from NAD and attach it to host cell protein)

28
Q

In Type III exotoxins, the ____ of the host cell protein either inactivates it or causes it to behave abnormally

A

ADP-ribosylation

29
Q

Diptheria, Cholera, and Shiga are examples of which exotoxin?
A. Type I
B. Type II
C. Type III

A

C. Type III

30
Q

The A portion of ADP-ribosylates elongation factor 2 in which of the following:
A. Diptheria
B. Cholera
C. Shiga

A

A. Diptheria

31
Q

What is the effect of the A portion of diptheria toxin?

A

To kill host cell by stopping protein synthesis

32
Q

____: The A portion of AB Toxin will add ADP-ribosylate to a regulatory enzyme that controls cAMP levels in host cell. It keeps enzyme from being turned OFF, causing host cell to lose control of ION FLOW. Diarrhea results.
A. Diptheria
B. Cholera
C. Shiga

A

B. Cholera

33
Q

The A subunit of the AB toxin cleaves a host cell rRNA molecule, which results in shutdown of protein synthesis in which pathogen?

A. Diptheria
B. Cholera
C. Shiga

A

C. Shiga

34
Q

What kind of antibodies are the body’s major defense against exotoxins?

A

Antitoxin antibodies

35
Q

True or False: Once the antibody binds to the exotoxin (B subunit) the toxin can no longer bind to receptors on host cell membrane

A

True

36
Q

Which toxin enters the blood stream, but some bacteria still remain in throat (toxemia)?
A. Cholera
B. Diptheria
C. Shiga

A

B. Diptheria

37
Q

Which toxin is made by clostridium and is a gram (+) obligate anaerobe, as well as a sporeformer?
A. C. diff
B. E. coli
C. Botulinum

A

C. Botulinum toxin

38
Q

True or False: Food borne botulism is an infection

A

False - food borne botulism is NOT an infection. Rather: it’s an intoxication…

39
Q

In botulism, target neurons attack ____ endings. Inside the neuron, the toxin blocks release of ____, a neurotransmitter.

A

peripheral; Ach

40
Q

Which two types of botulism involve COLONIZATION of the bacteria, followed by toxin production?

A

Wound botulism and infant botulism

41
Q

What three toxins are produced by clostridium botulinum toxin?

A
  1. Botox (botulinum)
  2. C2 toxin
  3. C3 toxin
42
Q

True or False: C2 and C3 toxin catalyze ADP-ribosylation of host cell proteins while C1 (botox) act on neurons

A

True

43
Q

True or False: Tetanus toxin, produced by clostridium tetani, can cause lockjaw

A

True

44
Q

True or False: Clostridium botulinism causes patient to develop spastic paralysis - primary effect of CNS

A

False - Clostridium Tetani does this

45
Q

Which toxin blocks release of inhibitors from inhibitor interneurons?
A. Botox toxin
B. Tetanus toxin

A

B. Tetanus toxin

46
Q

Both ___ and ___ are neurotoxins

A

Botulism and Tetanus

47
Q

Both Botulism and Tetanus share AA sequence similarity with zinc-requiring endopeptidase, which cleaves a set of proteins known as _____

A

synaptobrevins

48
Q

____ are found in synaptic vesicles of neurons, the vesicles responsible for release of NT and inhibitory mediators

A

Synaptobrevins

49
Q

Why do Botulism and Tetanus cause such different effects?

A

Cell specificities of the binding regions of the two toxins

50
Q

Botulinum toxin targets ___ neurons while tetanus toxin acts on ______

A

peripheral; CNS

51
Q

Which toxin cleaves SNARE’s, thereby preventing neuro-secretory vesicles from docking/fusing with the nerve synapse plasma membrane and releasing their neurotransmitters?
A. Diptheria
B. Clostridium
C. Botulin

A

Botulin toxin

52
Q

___ toxin, produced by clostridium perfringens, contribute to gangrene by killing host cells and utilizing phospholipase activity
A. Alpha toxin
B. Beta toxin
C. Gamma-toxin

A

Alpha-toxin

53
Q

Alpha toxin is a:
A. Type 1 Toxin
B. Type 2 Toxin
C. Type 3 Toxin

A

B. Type 2 Toxin (membrane disrupting)

54
Q

True or False: Alpha-toxin targets many cell types and hydrolyzes lipid lecithin in mammalian cell membranes

A

True

55
Q

Which pathogen contributes to toxic shock syndrome?

A

Toxic shock syndrome pathogen

56
Q

True or False: Staphylococcus aureus produces most TSST (toxic shock syndrome toxins)

A

True

57
Q

TSST is a
A. Type 1 toxin
B. Type 2 toxin
C. Type 3 toxin

A

A. Type 1 toxin
- supertoxin

58
Q

What is the target cell for TSST (Toxic shock syndrome toxin-1)?
A. T Cells
B. B cells
C. Both B and T Cells
D. Macrophages

A

T cells

59
Q

True or False: TSST causes non-specific binding of T cells macrophages, elicits cytokine production by T cells, and produces fever

A

True

60
Q

Which toxin produces Pasturellosis? Is it gram (+) or gram (-)?

A

Pasteurella multocida toxin (PMT) - gram negative

61
Q

True or False: Pasteurella multocida toxin causes bone/weight loss, as well as lung destruction

A

True

62
Q

Which toxin binds the gangliosides receptor and enters cell via receptor mediated endocytosis?
A. TSST
B. Diptheria
C. Clostridium dificil
D. Pasteurella multocida toxin

A

Pasteurella multocida toxin

63
Q

True or False: Pasteurella multocida toxin turns the G protein OFF, which permanently disrupts regulation of cellular activities

A

False - Pasteurella multocida toxin turns the G protein ON, which permanently disrupts regulation of cellular activities

64
Q

True or False: Pasteurella multocida toxin is a type III toxin

A

True

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