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USMLE microbiology > virulence > Flashcards

virulence Flashcards

1
Q

which virulence factorr is key for staph aures ?

A

protein A

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2
Q

how does protein A work ?

A

inhibits phagocytosis by binding the Fc portion prevents the activation of the immune system and no opsonization happens and no compliment is activated

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3
Q

what bacteria are associated with the IgA protease cleavage factor ?

A

SHiN
s pneumonia
haemophilus influenza b
neisseria

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4
Q

how does IgA proteas works ?

A

cleavage of gA allows for thee invasion of mucosal surfaces

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5
Q

what bacteria uses thee M protein as a virulence factor ?

A

group A strep
associated with rheumatic fever
due too molecular mimicry

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6
Q

what are the post strep complicatons ?

A

rheumatic heat disease
glomerulonephritis

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7
Q

what determines what post strep complication you get ?

A

depends on he M protein subtype
strains that cause impetigo will result n GN
strains that cause pharyngitis will cause rheumatic fever

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8
Q

main differences between endo and exotoxins ?

A

endotoxins are only secreted by gram negative bacteria when they die (LPS)

exotoxins are proteins synthesised by bacteria

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9
Q

what are the feeatures associated with endotoxins ?

A

all produced by gram negative bacteria
all have a lipid a core
O antigen

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10
Q

how do endotoxin present as illness?

A

they allow for the release of IL 2 and TNF

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11
Q

why cant we make vaccines against endotoxins ?

A

weak antibody response

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12
Q

what are the immune responses associated with LPS ?

A

macrrophage - IL 1 , TNF and nitrric ooxide
complement - C3a releasee , C5a relas
tissuee factor - coagluation and DC

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13
Q

what is thee endotoxin receptor ?

A

CD14

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14
Q

what are the different mechanisms associated with exotoxins ?

A

inhibition of protein synthesis
increase fluid secretion
inhibit phagocytic ability
inhibit release of neurotransmitters

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15
Q

which bacteria are associated with exotoxins that inhibit protein synthesis ?

A

diphtheria
pseudomonas
shigella
enterohaemorrrhagic E coli

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16
Q

what are the toxins associated with diphtheria and pseudomonas and what is their mechanism of action ?

A

diphtheria toxin
exotoxin A
both allow for the ADP ribosylation off EE2F elongation factor

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17
Q

what is the toxin associated with shigella and what is thee mechanism of action ?

A

shiga toxin binds to the 60 S subunit off ribosomes
shiglla invadess thee host cell

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18
Q

what is the presentation off diphtheria ?

A

membranous lymphadenopathy
bulls neck

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19
Q

what is the presentation of shigella infection ?

A

infectious diarrhea

20
Q

what s thee virulence factor associated with E E.coli ?

A

shiga like toxin
also binds to 60 S portion of ribosomes
causes bloody diarrhea

21
Q

what are the two classic examples associated with systemic reactions to endotoxins ?

A

meningococcemia
gram negative sepsis

22
Q

what is the man mechanisms of disease n shigella vs in E.Ecoli?

A

shigella - invasion of inteestiinal cells
e.col - through toxn releasee

23
Q

what happens upon the release of shiga toxin into the blood ?

A

hemolytic uremic syndrome
only associated with E E coli

24
Q

what are the bacteria that release exotoxins that. increase fluid secretion ?

A

entrotoxigenic e coli
bacillus anthrax
cholera

25
Q

how do clls in the GI tract secrete fluids ?

A

the more chlorine out
the more water in

26
Q

what is the chlorine controlled by in the GI tract ?

A

CFTR gene

27
Q

what must bee done to increase chlorine secretion ?

A

activate Gs or AC

28
Q

what are the toxins associated with enterotoxigenic e coli ?

A

heat labile exotoxin - activate cAMP
heat stable exotoxin- activates cGMP

29
Q

what are the three proteins associated with bacillus anthrax ?

A

protective antigen
lethal factoor
edema factor

30
Q

what is the edma toxin compromised of ?

A

PA + EF

31
Q

what. does edema toxin mimic ?

A

adenyl cyclase

32
Q

what is the presentation of anthrax ?

A

lung affection - necrotizing pneumonia
skin affection - black escharin
GI - ulcers

33
Q

what is thee toxin associated with cholera ?

A

cholera toxin
overactivates cAMP
Gs is always active

34
Q

what are the bacteria that inhibit phagocytosis ?

A

bordatella pertussis
pertussis toxin G inhibitory protein inactivation so over activation of adenylate cyclase

35
Q

which bacteria are associated with the inhibition of neurotransmitters and the associated toxins ?

A

clostridium tetani - tetanospasmin
clostridium botulinum -botlinium toxin

36
Q

what is the mechanism of action associated with the toxins from bacteria that inhibt neurotransmitters ?

A

tetanospasmin - rigid paralysis
botulinim - flaccid paralysis

37
Q

what type of cells does tetanospasm work on ?

A

reenshaw cells

38
Q

what bacteria release exotoxins associated with the lysis of cell membrane and what are the toxins associated ?

A

clostridium perferengens - alpha toxin
strep pyogens - streptolysin O

39
Q

what is the mechanism of action off alpha toxin ?

A

phospholipase that degrades tissue and cell membranes
causes myonecrosis gas gangrene

40
Q

what is the mechanism off action of streptolysin O ?

A

protein that degrades cell memb

41
Q

what is seen on blood agar with strep pyogens ?

A

double zone of hemolysis

42
Q

what are the toxoid vaccines ?

A

DTaP
diphtheria and tetanus and acellular pertussis

43
Q

what are superantigens ?

A

a type of exotoxin that causes a huge recruitment of T cells
hue release of IL 2 and IFN gamma

44
Q

what are the 2 bacteria associated with superantigens ?

A

staph aureus TSST 1
strep pyogens A or C

45
Q

what clinical scenarios are associated with TSS ?

A

staph and packing
women with tampon
surgical wound with packing

46
Q

how can TSS seperated from sepsis ?

A

TSS , resemble a sunburn with desquamation of the hand ad the soles
diarrhea is also common in TSS but not in sepsis

47
Q

what is staph TSS commonly associated with ?

A

strep TSS

USMLE microbiology (9 decks)

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