Gram-Positive Agent Characteristics

Question 1

What five classes/antibiotics demonstrate concentration-dependent bactericidal activity?

Answer 1

Aminoglycosides, daptomycin, fluoroquinolones, metronidazole, lipoglycopeptides

Question 2

What are the four resistance mechanisms found in streptococcus pneumoniae and what antibiotics are affected?

Answer 2

Changes in PBP: beta-lactam antibiotics (except ceftriaxone, cefotaxime)
ermB gene: changes in ribosome (clindamycin + macrocodes)
gyrase change: fluoroquinolone
Efflux (mefA): macrolide resistance only

Question 3

What major drug interaction is observed with Quinupristin/dalfopristin?

Answer 3

CYP 3A4 inhibitor

Question 4

What major drug interaction is observed with the oxazoledinones (linezolid/tedezolid)?

Answer 4

MAO inhibitor – risk of serotonin syndrome and pressor response

Question 5

What is the major drug interaction with daptomycin?

Answer 5

Statins – may synergistically increase risk of myopathy

Question 6

What two drugs have a drug-lab interaction and what is that interaction?

Answer 6

Telavancin and oritavancin; coagulation tests PT, aPTT, INR

Question 7

What agents (exam 1) have activity versus anaerobes?

Answer 7

piperacillin, Zosyn, Unasyn, Augmentin, Timentin, cefoxitin, cefotetan, carbapenems, and vancomycin (gram-positive)

Question 8

What are the major adverse effects of vancomycin?

Answer 8

nephrotoxicity, ototoxicity, red man syndrome, interstitial nephritis, and thrombophlebitis

Question 9

What are the risk factors for nephrotoxicity with vancomycin?

Answer 9

Renal insufficiency, prolonged therapy, high dose, high trough level, concurrent use of other nephrotoxic agents

Question 10

What are the primary adverse effects associated with Synercid?

Answer 10

myalgia, arthralgia, venous irritation

Question 11

What are the primary adverse effects associated with linezolid/tedezolid?

Answer 11

Optic and peripheral neuropathy, thrombocytopenia (don’t start if plt <50), anemia

Question 12

What are the primary adverse effects associated with daptomycin?

Answer 12

Acute eosinophilic pneumonia, myopathy with CPK elevation

Question 13

What are the primary adverse effects associated with telavancin?

Answer 13

QTc prolongation, taste disturbance, nephrotoxicity, red man syndrome (only one shared with other lipoglycopeptides)

Question 14

According to Erdman, what is the PKPD characteristic that predicts efficacy for linezolid?

Answer 14

T > MIC, bacteriostatic

Question 15

What two antibiotics cover VRSA?

Answer 15

Daptomycin, linezolid

Question 16

What VRE-targeting antibiotic only covers E. faecium and not E. faecalis?

Answer 16

Synercid

Question 17

What agents cover PRSP (so far)?

Answer 17

Ceftriaxone, cefotaxime, cefepime, ceftaroline, vancomycin, linezolid, daptomycin, synercid, lipoglycopeptides

Question 18

What agents cover MRSA (so far)?

Answer 18

Ceftaroline, vancomycin, synercid, linezolid, daptomycin, lipoglycopeptides

Question 19

What agents cover VRE?

Answer 19

Synercid (if faecium), linezolid, daptomycin, oritavancin, and telavancin/dalbavancin (only against some b/c same MOR)

Question 20

What agents (so far) cover pseudomonas?

Answer 20

Penicillin: Ticarcillin, piperacillin, Timentin, Zosyn
Ceph: ceftazidime, cefoperazone, combo with BL
Carbapenem: all except ertapenem
Aztreonam

Question 21

What gram-positive agents can penetrate into the CSF?

Answer 21

Vancomycin variable, linezolid 30%

Question 22

What gram-positive agents must be adjusted in renal insufficiency?

Answer 22

vancomycin, daptomycin, dalbavancin, telavancin

Question 23

What gram-positive agents are removed by hemodialysis?

Answer 23

if new dialyzer, vancomycin can be removed a small amount (30%).
Linezolid/tedezolid are removed

Question 24

What drugs can demonstrate cross-resistance with vancomycin?

Answer 24

Telavancin and dalbavancin – also inhibited when D-Ala-D-Ala changes to D-Ala-D-Lac. Oritavancin is not.

Question 25

What is the mechanism of resistance behind VISA?

Answer 25

Thickening of the staph aureus cell wall. increases the MIC to vancomycin.

Question 26

What gram-positive antibiotic inhibits the formation of the ribosomal 70S complex?

Answer 26

Linezolid/tedezolid

Question 27

What gram-positive antibiotic aggregates in the cell walls of bacteria, poking holes in the wall?

Answer 27

Daptomycin

Question 28

Is Synercid bacteriostatic or bacteriocidal?

Answer 28

By using quinupristin/dalfopristin together, Synercid can be bactericidal (per Cushman) for some organisms (per Erdman)

Question 29

What are the only gram-positive targeting abx that are available orally?

Answer 29

Linezolid/tedezolid

oral vancomycin for c. diff

Question 30

What are the only differences between linezolid and tedezolid?

Answer 30

Tedezolid has greater potency against MRSA and has once daily dosing. Otherwise, less evidence base.