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Medical Microbiology > Lecture 4 > Flashcards

Lecture 4 Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

Define “virulence factors”

A

pathogen-produced products that aid in the establishment and maintenance of infectious disease

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2
Q

What are some types of virulence factors?

A

siderphores, adhesins, toxins, proteolytic enzymes, LPS, capsules, peptidoglycan, and factors that will help them spread

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3
Q

What are adhesins?

A

mediate binding of microbe to some kind of surface

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4
Q

What are invasins?

A

type of adhesin that mediates binding and entry into host cell

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5
Q

What are microbial toxins?

A

product of microbial pathogen that can damage host

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6
Q

What are the 2 types of toxins and what are they based on?

A

based on location inside the cell = can be an endotoxin or exotoxin

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7
Q

What is an exotoxin?

A

made in cytoplasm –> released outside of bacterial cell

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8
Q

What is an endotoxin?

A

made in cytoplasm –> STAYS INSIDE of bacterial cell

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9
Q

What is a characteristic of endotoxins?

A

cell-bound; released in LARGE amounts ONLY when lysed; weak toxicity without being lysed

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10
Q

What is the most studied endotoxin?

A

lipopolysaccharide from gram–

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11
Q

What mode of action do endotoxins have and what does it mean? General or specific?

A

general = all of them work the same way and do the same thing

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12
Q

Are endotoxins ever released if not lysed? If so, how?

A

No, cannot be released without lysis

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13
Q

What part/domain is responsible for the endotoxin activity?

A

Lipid A (base of LPS)

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14
Q

What are symptoms caused by LPS?

A

low conc = fever and stimulates host cell’s immune system; high conc = toxic shock and death

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15
Q

What dictates the symptoms of LPS?

A

the concentration of LPS

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16
Q

What are characteristics of exotoxins?

A

found in all types of bacteria, actively secreted by bacteria

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17
Q

What mode of action do exotoxins have and what does it mean? General or specific?

A

specific and active mechanism

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18
Q

At least at what concentration are exotoxins highly toxic?

A

low concentrations

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19
Q

What are 4 ways exotoxins can be named?

A

based on target (ie:neurotoxin); species that made it (ie: tetanus toxin); activity (ie: proteolytic toxin); by letter (ie: exotoxin A)

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20
Q

What are the 3 different types of exotoxins?

A

super-antigen toxins (I); cytolytic toxins (II); A-B toxins (III)

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21
Q

What are super-antigen toxins?

A

they stay outside the host cell bound onto its surface; does not invade/enter cell

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22
Q

What mode of pathogenesis do super-antigen toxins take?

A

drive the host immune system to attack these host cells (host attacking itself)

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23
Q

What are cytolytic toxins?

A

enters and damages host-cell cytoplasmic membrane = makes an opening/pore –> allows release of cytosol = cell lysis

24
Q

What is an example of a cytolytic toxin?

A

hemolysins

25
Q

What mechanism of infection do cytolytic toxins do?

A

synthesized as a polymer then enters host cell and creates a polymer = forming a pore/opening = increaing permeability

26
Q

What are A-B toxins?

A

either whole or part of toxin will enter host cell

27
Q

What mechanism of infection do A-B toxins do?

A

A-domain enters host cell and B-domain stays on cell surface receptor; A-domain = exotoxin activity

28
Q

How many subunits can each domain have in A-B toxins?

A

from one to multi

29
Q

What are 4 cell damage/death mechanisms do toxins cause?

A

host cell lysis, induction of premature apoptosis, immunoresponse (ie: super-anitgen toxins), and change in metabolism

30
Q

What are 2 ways can bacteria lyse host cells?

A

destruction of cell membrane or over-multiplication of pathogen inside host cell

31
Q

How will lysing the host cell benefit bacteria? Is this lysis activity active or passive?

A

provides nutrients and space to grow for bacteria; passive activity, does not mean to kill cells

32
Q

On a blood agar plate, what would signify hemolysin activity?

A

a clearing around a bacterial colony

33
Q

Why would bacterial pathogens target RBCs?

A

they don’t necessarily target RBCs (passive activity); but it provides as a source of iron

34
Q

What is beneficial about using a blood agar plate assay?

A

to determine if bacteria produces a type II exotoxin (cytolytic exotoxin)

35
Q

What bacterial species produces diptheria toxin?

A

Corynebacterium diptheriae

36
Q

What type of toxin is diptheria toxin? How does it affect the host cell?

A

A-B toxin; premature stop in protein synthesis

37
Q

What is the mode of infection of diptheria toxins?

A

protease cleaves A-B domains and allows A-domain to enter cell –> A-domain targets and modifies EF2 of ribosome = inhibits tRNA binding to ribosome

38
Q

What is the mode of infection of botulinum toxin?

A

blocks and prevents release of Ach = reduces and inhibits muscle fiber contractions –> paralysis and death

39
Q

What species produces botulinum toxin and what kind of exotoxin is it?

A

clostridium botulinum; neurotoxin

40
Q

Where is diptheria toxin found?

A

viruses genome — bacteriophage which infects corynebacteria diptheriae

41
Q

How do we measure the lethality of a toxin?

A

based on its lethal dose by ng/kg (based on weight)

42
Q

What does LD50 stand for?

A

the lethal dose that killed 50% of people in a study

43
Q

What is the FIRST MOST lethal toxin in the world? What is the second?

A

Botulinum toxin, tetanus toxin

44
Q

What is the LD50 of botulinum toxin?

A

2ng/kg

45
Q

What kind of toxin is tetanus toxin and which species produce it?

A

neurotoxin, clostridium tetani

46
Q

What is the LD50 of tetanus toxin?

A

3ng/kg

47
Q

What is the mode of infection of tetanus toxin?

A

prevents release of glycine from neurons = can’t stop Ach release = can’t relax muscle = constant muscle contractions = paralysis/death

48
Q

What type of toxin is cholera enterotoxin and which species produces it?

A

A-B toxin by vibrio cholerae (gram–)

49
Q

How many subunits do the A and B domains of cholera enterotoxin have? What is significant about the A-domain?

A

1 A and 5 B; A-domain has adenyl cyclase activity

50
Q

Which part of the GI tract do enterotoxins act on?

A

intestines

51
Q

What is the main symptom caused by cholera enterotoxin?

A

watery diarrhea

52
Q

What is the mode of infection of cholera enterotoxin?

A

A-domain converts ATP to AMP = causes movement of ions from blood into lumen = changes concentration gradient = makes water move with ions into lumen = watery diarrhea

53
Q

What are 3 applications of toxins?

A

vaccine development (toxoid), medical uses (ie: botox); biological weapons

54
Q

The B portion of A-B toxins is being used as vaccine components without chemical treatment. Why is it safe to use the B portion as they are?

A

B-portion has no toxic activity

55
Q

Why is vaccination usually best way to prevent disease caused by A-B toxins?

A

You can use the A-B toxin as an antigen that your immune system will recognize and target this toxin

56
Q

Why is it better to create a vaccine to target toxins/virulence factors than against the bacteria itself

A

you may kill/lyse bacteria = release endotoxins; targeting virulence factors decreases the symptoms of the disease

57
Q

How does diptheria toxin contribute to bacterial pathogenesis?

A

inhibits/prematurely stops protein syntheses

Medical Microbiology (20 decks)

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