staphylococcus aureus Flashcards

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1
Q

Staph aureus is coagulase? and catalase?

A

catalase and coagulase +

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2
Q

how do colonies of stap aureus look like?

A

yellow colonies in mannitol salt agar

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3
Q

Staph aureus can tolerate high concentration of what substance?

A

salt

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4
Q

where does stap aureus ferment?

A

in mannitol

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5
Q

Staph aureus is resistant to what?

A

1) penicillin
2) methicillin
3) vancomycin

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6
Q

why is stap aureus resistant to penicillin?

A

it has penicillinase

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7
Q

what is used for treatment when there is resistance to penicillin?

A

oxacillin

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8
Q

why is staph aureus resistant to methicillin (MRSA)?

A

it modifies PBP which has low affinity for beta lactam drugs

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9
Q

how do you treat methicillin resistant staph aureus?

A

vancomycin

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10
Q

how does staph aureus become resistant to vancomycin (VRSA)?

A

converts D-Ala-D-Ala to D-Ala-D-Lac

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11
Q

what is used to treat VRSA?

A

quinupristin and dalfopristin

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12
Q

what illnesses are related to toxins from staph aureus? (3)

A

staph scalded skin syndrome = exfoliate toxin

food poisoning = enterotoxin

Toxic Shock Syndrome = TSST-1

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13
Q

what enzymes does staph aureus produce?

A

catalase

coagulase

protein A

cytolytic toxins

enterotoxins

exfoliative

toxic shock syndrome toxin-1 (TSST-1)

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14
Q

what is toxic shock syndrome toxin-1?

what is its onset?

what symptoms are seen?

A

it is a superantigen where there is non-specific activation of T lymphocytes and consequent release of a large number of cytokines

it has an acute onset

fever, hypotension, multiple system organ failure

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15
Q

what do the exfoliative enzymes of staph aureus cause?

what is seen with this?

what age must people have for this to happen?

what is a complication that can happen with the disease caused by exfoliative enzymes of staph aureus?

A

Staph scalded skin syndrome (SSSS),

A-B toxin targets epithelial cells and breaks it (targets tight junctions and desmosomes)

on children 6 or below

bullous impetigo (localized SSSS), will have impetigo but with fever

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16
Q

what will cytolytic toxins do?

A

will destroy cell membranes

17
Q

what will protein A do?

A

inhibit phagocytosis by binding to Fc portion

18
Q

what will coagulase secreted by staph aureus cause?

A

abcesses

19
Q

what will secreted enterotoxins by staph aureus cause?

what time does it take to incubate? how long until it resolves?

what foods can have staph aureus secreting enterotoxins

A

food poisoning (nausea, vomit, no poop)

incubation: 2-6 hrs
resolves: 24 hrs
foods: potato salad, custards, ham, ice cream

20
Q

what infections or diseases can be caused by staph aureus?

A

1) skin lesions
2) acute endocarditis
3) osteomyelitis
4) septic arthritis
5) pneumonia
6) nococomial infections

21
Q

what skin infections are caused by staph aureus?

A

abcesses, folliculitis, impetigo-> (superficial skin infections in kids)

22
Q

how does staph aureus cause acute endocarditis?

who is most at risk?

what part of the heart is most at risk with acute endocarditis?

A

by being prolonged to staph bacteremia

IV drug users

tricuspid valve

23
Q

what is the most common cause of septic shock in children and young adults?

A

staph aureus

24
Q

what is the most common cause of septic shock in sexually active individuals?

A

Nisseria gonorrhea

25
Q

what will osteomyelitis from staph aureus cause in adults?

A

flat bones

26
Q

what will osteomyelitis from staph aureus cause in children?

A

affect elongation of long bones

27
Q

what is the most common cause of osteomyelitis in people with sickle cell or thalassemia?

A

salmonella

28
Q

what is the most common cause of osteomyelitis?

A

staph aureus

29
Q

who gets pneumonia due to staph aureus?

A

predisposed people with diseases like: CGD (chronic granulomatous disease), CF (C. Fibrosis)

30
Q

if a patient has lobular pneumonia due to staph aureus, what will there be a high rate of?

A

abcess formation

31
Q

for Toxic shock syndrome, a blood culture will be + or -?

A

negative

32
Q
A
33
Q

how do you distinguish between bullous impetigo and staph scalded syndrome?

A

bullae from impetigo will have the bacteria as staph scalded s. will not have the bacteria present in lesions