More antibiotics

Question 1

Which macrolide is contraindicated during pregnancy?

Answer 1

clarithromycin

Question 2

Name all the macrolides.

Answer 2

erythromycin, clarithromycin, dirithromycin, troleandomycin, azithromycin

Question 3

Which two macrolides do not inhibit cyto-P450 enzyme?

Answer 3

azithromycin and dirithromycin

Question 4

Macrolides can cause what serious side effect?

Answer 4

prolongation of QT interval; cardiac arrhythmias

Question 5

Which macrolide is acid unstable and therefore is enteric coated?

Answer 5

erythromycin

Question 6

What is the mechanism of action of macrolides?

Answer 6

blocks 2 steps; translocation of A site to P site and transpeptidation of nascent polypeptide chain

Question 7

Name the lincosamides.

Answer 7

Lincomycin; clindomycin

Question 8

Name the macrolide spectrum.

Answer 8

intermediate, static, 50s

Question 9

Name the lincosamide spectrum

Answer 9

narrow, static, 50s

Question 10

What is the mechanism of action of lincosamides?

Answer 10

same as macrolides (blocks translocation of a site to p site; blocks transpeptidation of polypeptide chain). Also on same binding site on 50s

Question 11

What are the toxicological effects of lincosamides?

Answer 11

hepatotoxicity, GI irritation (less so with clindamycin)

Question 12

What is the MoA of dalfopristin?

Answer 12

Binds to a nearby site, causing a conformational change and enhancing the binding of quinupristin. Also interferes with polypeptide-chain formation

Question 13

How does quinupristin work?

Answer 13

binds to the same location on the 50s as macrolides and lincosamides

Question 14

What is the mechanism of resistance against quinupristin specifically?

Answer 14

production of lactamases to inactivate quinupristin, ribosomal alteration so it can’t bind

Question 15

What is the mechanism of resistance against dalfopristin specifically?

Answer 15

production of acetyltransferases to inactivate it, production of ATP binding efflux proteins

Question 16

What do streptogrammins inhibit?

Answer 16

the drug metabolizing enzyme CYP3A4

Question 17

What is the activity of streptogrammins

Answer 17

CIDAL on 50s (spectrum possibly broad)

Question 18

What are streptogrammins indicated for?

Answer 18

VREF (vancomycin-resistant enterococcus faecium) and resistant staph infections

Question 19

Describe the activity of the ketolides

Answer 19

intermediate spectrum, cidal, 50s

Question 20

Name the ketolides

Answer 20

telithromycin ONLY

Question 21

What is the indication for telithromycin?

Answer 21

community-aquired ammonia of mild to moderate severity

Question 22

How does the mechanism of resistance affect ketolides?

Answer 22

because telithromycin binds at two different spots on the 50s rRNA, methylases do not inhibit their activity; they only affect the site that telithromycin shares with erythromycin. Telithromycin retains its activity against gram + cocci

Question 23

Why do ketolides have a higher risk of side effects?

Answer 23

they inhibit the CYP3a4 isozyme, which results in increased plasma levels of the drug and increases the side effects

Question 24

Ketolides have what specific side effects?

Answer 24

prolonged Q-T interval and ventricular arrhythmias (DO NOT mix with macrolides), acute liver failure and severe liver injury, visual disturbances, transient loss of consciousness

Question 25

Ketolides are poor substrates for

Answer 25

bacterial protein pumps that mediate active efflux of macrolides

Question 26

Describe the activity of Chloramphenicol

Answer 26

static, broad, 50s

Question 27

What population is chloramphenicol contraindicated for and why?

Answer 27

newborns; they lack the glucuronyl transferase enzyme - the enzyme that metabolizes the drug. This enzyme is present in the liver

Question 28

What is the MoA of chloramphenicol?

Answer 28

inhibits transpeptidation (same as macrolides and lincosamides), but it binds to a site near them, so they are allosteric antagonists

Question 29

Describe the toxicity of chloramphenicol.

Answer 29

Inhibits vitamin K production, increases EtOH intolerance, immunodepression, bone marrow depression, aplastic anemia

Question 30

Describe the activity of the oxazolidinones

Answer 30

static, gram + only, 50s

Question 31

Name the oxazolidinones

Answer 31

linezolid, tedizolid

Question 32

What is the MoA of oxazolidinones?

Answer 32

bind to the P-site - preventing the formation of the ribosomal-fMET-tRNA complex and inhibiting the ribosome assembly step

Question 33

What is the mechanism of resistance against the oxazolidinones?

Answer 33

mutation of the binding site (linezolid)

Question 34

What is the toxicity of the oxazolidinones?

Answer 34

PMC (pseudomembranous colitis) and thrombocytopenia

Question 35

What should not be taken with linezolid?

Answer 35

antidepressants, MAOIs, adrenergic agents

Question 36

What are the oxazolidinones indicated for?

Answer 36

VREF, nosocomial pneumonia, community acquired pneumonia caused by staph infections

Question 37

Name the pleuromutilins.

Answer 37

retapamulin only

Question 38

Describe the activity of the pleuromutilins

Answer 38

static (low concentrations) cidal at high, 50s

Question 39

What are the pleuromutilins indicated for?

Answer 39

skin infections caused by strep and staph aureus - topical

Question 40

What is the MoA of retapamulin?

Answer 40

inhibits p-site interactions, inhibits the enzyme peptidyl transferase, prevents formation of normal acting 50s

Question 41

What is the mechanism of resistance against retapamulin?

Answer 41

ribosomal alteration, active efflux *no cross resistance*