C.16. Clindamycin. Streptogramins. Oxazolidinones.

Question 1

what class of Ab does Clindamycin belong to?

Answer 1

Lincosamides

*lincomycin

Question 2

what is the mechanism of action of Clindamycin?

Answer 2

similar to macrolides
binds to the 50s subunit, blocks protein synthesis
bacteriostatic effect

Question 3

what is the spectrum and clincal use of Clindamycin?

Answer 3

narrow (9):

1. gram + cocci
2. staph and strep. skin and soft tissue infection
3. community-acquired MRSA
4. Osteomyelitis (by staph)
5. endocarditis prophylaxis
6. pneumonitis jirovecii, toxoplasmosis
7. polymicrobial infections of the GI and female genital tract (with Aminoglycosides)
8. B. fragilis infection (lung abscess) -anaerobe infections
9. acne (topical)

Question 4

what is the metabolism of Clindamycin?

Answer 4

hepatic

excreted in the bile and urine both intact and metabolized

Question 5

absorption of Clindamycin

Answer 5

80-90% , good

↑ concentration on abscess and bones

Question 6

what is the mechanisms of resistance of Clindamycin?

Answer 6

1. methylation of ribosomal binding site
2. enzymatic inactivation
3. poor penetration via the outer membrane of gram - bacteria (intrinsic resistant)

Question 7

side effects of Clindamycin

Answer 7

GI symptoms 
skin rash
Neutropenia
Hepatotoxicity
C. difficile superinfection (pseudomembranous colitis)

Question 8

mechanism of action of streptogramin (Quinuproistin, Dalfopristin)

Answer 8

binds to the 50s ribosomal subunit, blocking the exit channel on the ribosome, through which nascent polypeptides are extruded
Bactericidal effect

Question 9

what is the ratio of the combination of Quinupristin and Dalfoprisitn?

Answer 9

30:70
Quinupristin: Dalfopristin

Question 10

what is the clinical use of Quinupristin with Dalfopristin?

Answer 10

effective against MRSA, PRSP, VRSA, and resistant strains of E. faecium
*considered as ‘reserve antibiotics’ for complicated resistant infections

Question 11

what is the clinical use of Quinupristin with Dalfopristin?

Answer 11

effective against MRSA, PRSP, VRSA, and resistant strains of E. faecium
*considered as ‘reserve antibiotics’ for complicated resistant infections

Question 12

how are streptogramins given?

Answer 12

IV

Question 13

dynamic properties of streptogramins

Answer 13

inhibition of CYP450 enzymes

↑ level of Benzo, warfarin

Question 14

mechanism of resistance to streptogramins

Answer 14

efflux pump

*E. faecalis is resistant

Question 15

side effects of streptogramins

Answer 15

arthralgia-myalgia syndrome
GI problems
↑ bilirubin
allergy

Question 16

mechanism of action of Oxazolidinon (Linezolid)

Answer 16

binds to the 50s ribosomal subunit. inhibits the formation of initiation complex in bacterial translation system
Bacteriostatic effect

Question 17

Clinical use of Linezolid

Answer 17

effective against multidrug-resistant gram + cocci

MRSA, PRSP, VRE

Question 18

how is Linezolid given?

Answer 18

oral or Parenteral

Question 19

important properties of Linezolid

Answer 19

Inhibitor of MAO-A and MAO-B –> possible risk of cheese reaction!
T1/2 4-6 hours
hepatic metabolism

Question 20

mechanism of resistance of Linezolid

Answer 20

altered affinity to the binding site

*resistant strains are rare

Question 21

side effects of Linezolid

Answer 21

myelosuppression: thrombocytopenia, Neutropenia (weekly blood control is needed)
optic neuropathy
Serotonin Syndrome (in combination with SSRI’S)

Question 22

how can clindamycin be given?

Answer 22

oral, parenteral, and topical (acne)