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HDID Block 2 > L35 > Flashcards

L35 Flashcards

1
Q

What is the microscopic morphology of staph?

A

GP - thick peptidoglycan layer

Cocci in clusters (grapes)

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2
Q

Is SA catalase positive or negative?

A

Positive

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3
Q

Is SA coagulase positive or negative?

A

Positive

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4
Q

Does SA have a polysaccharide capsule or slime layer?

A

Both
Capsule - protection from phagocytosis
Slime - adherence

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5
Q

What color is SA on blood agar?

A

Yellow/gold

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6
Q

What are the 6 virulence factors for SA?

A
  1. Capsule
  2. Protein A
  3. MSCRAMM surface adhesion proteins
  4. Enzymes for tissue destruction
  5. Toxin mediated tissue destruction
  6. Penicillinase/antibiotic resistance
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7
Q

What is protein A?

A

Cell wall protein that binds IgG @ Fc so the Abs can’t mark the bug for phagocytosis
Also binds VWB factor to help with platelet adhesion for increased virulence

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8
Q

What are some examples of enzymes SA uses for virulence?

A

Coagulase - microthrombus formation
Catalase - inactivates Hperoxide (killing mechanism)
Lipases & nucleases that hydrolyze lipids & DNA

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9
Q

How do the cytotoxins SA produces help its survival?

A

Cytotoxins are always produced (vs cytolytic peptides = sometimes)
Lyse cell membranes to destroy immune cells

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10
Q

What toxin does SA produce yielding scalded skin syndrome?

A

Exfoliative toxins

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11
Q

What toxin does SA produce yielding food poisoning?

A

Enterotoxin

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12
Q

What toxin does SA produce yielding shock?

A

Toxic shock syndrome toxin 1

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13
Q

What are the mechanisms by which SA is drug resistant?

A
  1. Penicillinase vs beta lactams

2. mecA –> PBP2a –> methicillin & semi-synthetic penicillins (nafcillin & dicloxacillin) resistance

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14
Q

How can SA become VISA?

A

= vanco resistance
Acquired from VRE (vanA to alter binding site)
See thickened cell wall that vanco gets stuck in

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15
Q

Is SA colonization common?

A

30% population

Nose

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16
Q

What skin/ST infections might present due to SA?

A

Pyogenic infections:

  • Impetigo
  • Folliculitis
  • Furuncle (boils)
  • Carbuncles
  • Wounds post surgery
17
Q

What metastatic infections may present due to SA?

A 
BACTEREMIA!!! 
Pneumonia
Osteomyelitis
Septic arthritis
Endocarditis
18
Q

What are the main virulence factors for coag negative staph?

A

Slime layer
Enzymes like SA
- But no toxins!

19
Q

What coag-neg staph typically infects prosthetic material?

A

S. epidermidis

20
Q

Which coag-neg staph causes UTIs?

A

S. saprophyticus

21
Q

Which coag-neg staph causes native valve endocarditis?

A

S. lugdenensis

22
Q

How do you diagnose SA?

A

Culture

  • See in blood = BAD, always assume it is real & treat it
  • Skin site only if near/at the site of infection (will be negative if the infection source is not there)
23
Q

How do you diagnose coag-neg staph?

A

Blood culture
- Could be false positive b/c went through the skin where colonies are normally high to take sample
- Need multiple positive samples to get conclusive diagnosis this way
Direct sample from prosthetic

24
Q

Quickly, you need to start treating a patient for staph infection before the cultures come back. What do you assume about the staph?

A

Assume penicillin & methicillin resistant

25
Q

You’re starting initial antibiotics for staph infection. If the patient is obviously sick - what are you choosing?

A

VANCO
Could go with dapto BUT not if the presentation is pneumonia
2nd choices: linezolid, ceftraroline

26
Q

You’re starting initial antibiotics for staph infection BUT patient isn’t super sick. Aka you can send them home with something PO. So what are you picking?

A 
Clindamycin 
TMP/SMX 
Doxycycline 
MRSA
Linezolid
27
Q

Cultures are back. The infection is serious & SUSCEPTIBLE. Which antibiotic are you going with?

A 
Anti-staph penicillins:
- Nafcillin 
- Cefazolin 
2nd choice if resistant/allergic:
- Vanco
- Dapto (if not pneumo)
28
Q

What is your choice for outpatient management of staph?

A 
1st = penicillins
- Dicloxacillin
- Cephalexin
2nd = resistant or allergic
- Clindamycin
- TMP/SMX - but may not cover strep
- Doxycyline for CA MRSA

HDID Block 2 (39 decks)

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