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STEP > ID 4 > Flashcards

ID 4 Flashcards

1
Q

c perfringens toxin

A

alpha toxin

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2
Q

alpha toxin mechanism

A

phospholipase (lecithinase) that degrades tissue and cell membranes

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3
Q

Alpha toxin manifestation on agar

A

hemolytic “double zone” of hemolysis on blood agar

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4
Q

what does alpha toxin lead to?

A

myonecrosis (“gas gangrene”)

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5
Q

strep pyogenes toxin?

A

streptolysin O

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6
Q

streptolysin O MOA

A

protein that degrades cell membrane, thus lysing RBCs

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7
Q

what do you use to diagnose ARF?

A

antistreptolysin o antibodies (ASO)

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8
Q

staph aureus toxin?

A

Toxic shock syndrome toxin (TSST-1)

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9
Q

strep pyogenes toxin?

A

Exotoxin A

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10
Q

TSST-1/exotoxin A MOA?

A

Bind to MHC II and TCR outside of antigen binding site to cause overwhelming release of IL-1, IL-2, IFN gamma, and TNF-alpha –> shock

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11
Q

staph aureus toxin causing scalded skin syndrome?

A

exfoliative toxin

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12
Q

staph aureus toxin causing food poisoning?

A

enterotoxin

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13
Q

LPS components

A

O antigen + core polysaccharide + lipid A

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14
Q

How is endotoxin released?

A

Upon cell lysis or *by living cells by blebs detaching from outer surface membrane.

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15
Q

main effects of endotoxin

A

1) macrophage activation (TLR4)
2) complement activation
3) tissue factor activation
* extremely heat stable

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16
Q

what other cytokine contributes to fever?

A

TNF-alpha

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17
Q

Macrophage cytokines causing hypotension?

A

TNF-alpha + nitric oxide

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18
Q

endotoxin and DIC mechanism

A

endotoxin –> tissue factor activation –> coagulation cascade –> DIC

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19
Q

how do you differentiate between alpha and beta-hemolysis on culture?

A

beta-hemolytic shows a clear area surrounding colony (see FA 119)

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20
Q

food poisoning scenario for staph aureus and why

A

Rapid-onset food poisoning. It’s preformed toxin that has a short incubation period (2-6 hr)

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21
Q

What is MRSA resistant to?

A

methicillin and *nafcillin because of altered penicillin-binding protein

22
Q

Labs in staphylococcal toxic shock syndrome

A

1) increased AST + ALT

2) increased bilirubin

23
Q

Differentiating staphylococcal toxic shock syndrome from streptococcus pyogenes TSS

A

1) staphylococcal presentation = fever + vomiting + rash + desquamation + shock + end-organ failure.
2) strep pyogenes toxic shock-like syndrome = painful skin infection

24
Q

S aureus food poisoning presentation

A

Non bloody diarrhea and emesis

25
Q

Problem with s aureus food poisoning

A

It’s a heat stable enterotoxin that isn’t destroyed by cooking.

26
Q

What is a staph abscess?

A

staph forms a fibrin clot around it’s itself.

27
Q

saprophyticus appearance

A

cocci in clusters

28
Q

Where is saprophyticus normally found?

A

Flora of female genital tract and perineum.

29
Q

second most common cause of uncomplicated UTI in young women?

A

saprophyticus

30
Q

Cause of sepsis in patients with sickle cell disease?

A

strep pneumo

31
Q

virulence factor of strep pneumo?

A

Capsule. Without it’s capsule, strep pneumo is not virulent.

32
Q

sputum with strep pneumo?

A

“rusty”

33
Q

viridans group streptococcus causing endocarditis

A

s sanguinis (sanguinis means blood)

34
Q

how do viridans group adhere to valves?

A

makes dextrans, which bind to fibrin-platelet aggregates on damaged heart valves.

35
Q

scarlet fever toxin

A

erythrogenic toxin

36
Q

How do you test for GBS

A

1) produces CAMP factor, which enlarges the area of hemolysis formed by S aureus (*NOT cAMP)
2) Hippurate test positive

37
Q

GBS prophylaxis?

A

intrapartum penicillin

38
Q

streptococcus bovis structure

A

gram positive cocci

39
Q

what is s gallolyticus?

A

S bovis biotype 1

40
Q

enterococci?

A

E faecalis
E faecium
VRE

41
Q

where are enterococci found?

A

normal colonic flora

42
Q

enterococci characteristisc?

A

penicillin G resistant

43
Q

VRE primary concern?

A

impt cause of nosocomial infection

44
Q

enterococci cause…

A

1) UTI
2) biliary tract infections
3) subacute endocarditis (*following GI/GU procedures)

45
Q

enterococci testing…

A

1) PYR positive
2) variable hemolysis
3) can grow in 6.5% NaCl
4) can grow in bile

46
Q

enterococci structure

A

Gram positive cocci in chains

47
Q

Unique thing about bacillus anthracis

A

Only bacterium with a polypeptide capsule (contains D-glutamate)

48
Q

cutaneous anthrax..

A

rarely progresses to bacteremia and death.

49
Q

cutaneous anthrax description

A

painless papule surrounded by vesicles that leads to ulcer with black eschar (painless, necrotic)

50
Q

pulmonary anthrax pathogenesis

A

inhalation of spores –> flu-like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis, and shock.

STEP (85 decks)

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