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Pharmacology > Antibiotics Effective Against MRSA and VRE > Flashcards

Antibiotics Effective Against MRSA and VRE Flashcards

1
Q

What occurs in MRSA?

A

Organism acquires resistance via another mechanism besides production of beta-lactamase. By altering its PCN binding protein, the protein which beta-lactams bind to, these medications to have no effect on this type of S. Aureus.

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2
Q

MRSA is a Gram ___ bacteria.

A

+

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3
Q

Which is the only beta-lactam that MRSA is not resistant to?

A

Ceftaroline

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4
Q

How is infection vs colonization of MRSA treated?

A

Infection: treat
Colonization: isolation

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5
Q

Which drugs are usually used to treat S. Aureus and why?

A

Methicillin, oxacillin, dicloxicillin, nafcillin

They are beta-lactamase resistant organisms

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6
Q

VRE can be either entercoccus faecium and/or faecalis and are both Gram _____ .

A

+
Faecalis is more common but not always vanco resistant
Faecium more likely to be resistant

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7
Q

What is the mainstay treatment of MRSA and enterococcus?

A

Vancomycin

not susceptible to beta-lactamase and binds to a different site than other PCN making is effective against MRSA

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8
Q

What is vancomycin’s MOA?

A

Inhibits cell wall synthesis

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9
Q

Is vancomycin bacteriostatic or bacteriocidal?

A

Cidal

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10
Q

How is vanco administered and why?

A

Large glycopeptide that has poor oral absorption so is primarily used IV

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11
Q

When would vanco be given PO?

A

C.diff d/t its local antibacterial effects

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12
Q

Vancomycin’s spectrum of action is against Gram ____ and what organisms?

A

+

MRSA, STACN, S. pneumoniae including pen-R

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13
Q

AE of vancomycin include:

A

Ototoxicity
Nephrotoxicity
Hypersensitivity
Red Man’s syndrome

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14
Q

How can Red Man’s Syndrome d/t vancomycin infusion be controlled?

A

Slow infusion rate
premedicate with antihistamine
(not an allergy)

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15
Q

How is vanco cleared from the body?

A

Renally

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16
Q

What are some instances when you would check a vanco trough?

A
  • Anticipated IV therapy for >4days (mod/severe inf)
  • Unstable renal function
  • Burns, morbidly obese, significant edema, cystic fibrosis
  • Pts on other nephrotoxic drugs (amphotericin B, aminoglycosides, cyclosporin)
  • Dialysis
  • Poor clinical response to vanco
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17
Q

What type of vanco level should be obtained in patients undergoing dialysis?

A

Random

18
Q

Why do we check troughs in patients taking vancomycin?

A

Vanco exhibits time dependent killing
Troughs are checked to see if the dose is above MIC or high enough. If the trough is within normal limits this means the patient had a high enough concentration for the entire dosing interval and therefore a high enough dose.

19
Q

When might a peak be recommended in patients taking vanco?

A

To confirm high serum concentrations to ensure adequate penetration into certain sites of infection (osteomyelitis, endocarditis, CNS infections)
**generally not required

20
Q

When is a vanco trough typically drawn and why?

A

30mins prior to the 3rd dose so that the drug has time to reach a steady state (if drawn during redistribution phase, may get a falsely high level)

21
Q

What is the suggested goal trough level of vanco?

A

Most inf: 5-15mcg/mL

CNS inf, MRSA HAP/VAP: 15-20mcg/mL

22
Q

What type of Streptogramin is used to treat MRSA and VRE (E. faecium) and what is its MOA, static/cidal, route of administration?

A

Synercid (Quinupristin/dalfopristin)
MOA: Inhibition of protein synthesis via action of 50S subunit
Cidal
IV

23
Q

AE and DI of Synercid:

A

AE: Infusion site effects, arthralgias, myalgias, increased transaminases
DI: Inhibition of CYP3A4

24
Q

Which drug used to treat VRE and MRSA acts to inhibit protein synthesis via inhibition of the 70S ribosomal initiation complex?

A

Linezolid

25
Q

What is one advantage of Linezolid?

A

PO in addition to IV

and effective for MRSA and both strains of VRE

26
Q

What AE and DI are associated with Linezolid?

A

AE: N/V/D, thrombocytopenia, elevated transaminases, leukopenia
DI/food: Inhibition of MAO= severe HTN if taken with tyramine rich foods and Serotonin Syndrome if taken with SSRI’s

27
Q

How does Daptomycin causes cell death?

A

Binds to cell membranes and causes cell death via rapid depolarization

28
Q

Daptomycin is used for the treatment of:

A

Broad spectrum

Gram + :MRSA, VRE (E. faecalis and faecium)

29
Q

Daptomycin may interact with what other type of drugs?

A

Statins (HMG CoA reductase inhibitors) causing increased myopathy, elevated CPKs

30
Q

AE of Daptomycin include:

A

N/V/C/D, dizziness, HA, insomnia, pruritis, rash

31
Q

What is the synthetic derivative of vanco and what is it used for?

A

Telavancin(IV)

MRSA complicated skin/subQ tissue infections

32
Q

How is televancin different from vanco?

A

Exhibits concentration dependent killing

33
Q

What type of patients should televancin never be used in?

A

Pregnancy

Black box warning, all women of child-bearing potential should be tested prior to administration

34
Q

What type of MRSA infections is ceftaroline (5th gen) recommended for?

A

skin infections

35
Q

How is ceftaroline (5th gen) similar to ceftriaxone (3rd gen)?

A

Both have good Gram - and even better Gram + coverage

usually 3rd gen abx do not have good Gram + coverage

36
Q

Which drug is similar structurally to tetracyclines and has good Gram + and - coverage and activity against MRSA?

A

Tigecycline

37
Q

How does Tigecycline work and is it cidal/static?

A

Inhibits protein synthesis by binding to the 30S subunit

Static

38
Q

AE of Tigecycline and patient population the drug should not be used in:

A

GI side effects

teeth discoloration and bone effects in children- do not use in pediatrics

39
Q

Which drugs can be used on an outpatient basis, usually for comm acquired MRSA?

A 
Clindamycin 
Bactrim (at higher doses than UTI)
Minocycline 
Doxycycline 
Mupirocin (topically)
Levofloxacin
40
Q

Why would Daptomycin not be given in patients with MRSA pneumonia?

A

Poor lung penetration

Pharmacology (48 decks)

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