Bacterial Protein Synthesis Inhibitors

Question 1

How does macrolide resistance come about?

Answer 1

1) Ribosomal methylation & reduced binding of macrolides to the 50S ribosomal subunit
2) Increased expression of efflux pumps

Question 2

What does Tetracyclines & Tigecyclines NOT cover?

Answer 2

Pseudomonas aeruginosa & Proteus

Question 3

MOA of Aminoglycosides

Answer 3

Block formation of initiation complex by causing misreading of codon

Question 4

Use of Aminoglycosides?

Answer 4

1) Empiric therapy for serious conditions
2) Aerobic Gram (-) & mycobacteria
3) 2nd line MDR tuberculosis

Question 5

Use of Tobramycin

Answer 5

Pseudomonas aeruginosa

Question 6

How are Aminoglycosides administered?

Answer 6

Parenterally (except Neomycin)

Question 7

ADE of Aminoglycosides

Answer 7

1) Nephrotoxicity & Ototoxicity
2) Neuromuscular paralysis
3) Hypersensitivity

Question 8

Use of Amikacin

Answer 8

WIDEST SPECTRUM
1) Proteus, P.aeruginosa, Enterobacter, E.coli,
Kebsiella (Gentamicin-resistant)
2) Mycobacterium TB

Question 9

How are Macrolides administered?

Answer 9

Oral/IV (Clarithromycin: Oral only)

Question 10

Coverage of Macrolides

Answer 10

Broad-spectrum, atypicals

Legionella, Chlamydia, Mycoplasma

Question 11

Use of Erythromycin

Answer 11

1) Community acquired pneumonia

2) S. pneumoniae

Question 12

Use of Clarithromycin

Answer 12

1) H.Pylori

2) Atypicals

Question 13

Use of Azithromycin

Answer 13

1) Respiratory infections
(H.influenzae, Moraxella catarrhalis)
2) STD (Chlamydia trachomatis, Neisseria gonorrhoea)

Question 14

Which of the bacterial protein synthesis inhibitors are safe for pregnancy?

Answer 14

Azithromycin, Erythromycin, Clindamycin

Question 15

Use of Clindamycin

Answer 15

Anaerobic, Gram (+) bacteria

1) Severe anaerobic conidtion
2) Clostridium perfringen
3) MRSA, Streptococcus
4) Dental

Question 16

Which agents can be used for MRSA?

Answer 16

1) Vancomycin
2) 5th gen cephalosporins (Ceftaroline, Ceftobiprole)
3) Doxycycline
4) Tigecycline
5) Clindamycin
6) Linezolid

Question 17

How are Macrolides cleared?

Answer 17

Hepatic

Question 18

ADE of Clindamycin

Answer 18

1) CDAD
2) Esophageal irritation
3) Skin rashes

Question 19

Coverage of Linezolid

Answer 19

Resistant Gram (+) strains
- MRSA, VRE, VRSA

Reserved for infections caused by multiple drug-resistant strains

Question 20

How is Tigecycline administered?

Answer 20

IV

Question 21

ADE of Linezolid

Answer 21

1) Bone marrow supression
2) GI effects
3) Serotonin syndrome
(avoid histamine & tyramine rich food)
4) Irreversible peripheral neuropathies

Question 22

Which agents can be used for community-acquired pneumonia?

Answer 22

1) Doxycycline
2) Tigecycline
3) Erythromycin

Question 23

What mechanisms of resistance were tigecycline designed to overcome?

Answer 23

1) Efflux pumps

2) Ribosomal protection

Question 24

How do bacteria gain macrolide resistance

Answer 24

1) ERM gene expression

2) Efflux pumps

Question 25

MOA of Tetracyclines

Answer 25

- Prevents binding of tRNA to A site of mRNA-ribosome complex -> Inhibiting protein synthesis

Question 26

Coverage of Tetracyclines

Answer 26

Broad spectrum (Gram (+) & (-)) - Atypical bacteria (Mycoplasma, Legionella, Chlamydia) - Spirochete bacteria - MRSA

Question 27

How should Tetracyclines be taken?

Answer 27

Oral (Empty stomach, avoid with dairy)

Question 28

ADE of Tetracyclines

Answer 28

- GI Discomfort - Effects on calcified tissues - Hepatotoxicity & Phototoxicity - Vestibular dysfunction - Superinfection

Question 29

Contraindications for Tetracyclines/Tigecycline

Answer 29

- Pregnancy - Breastfeeding - Child < 8yo

Question 30

How did resistance to Tetracyclines come about?

Answer 30

1) Efflux pumps | 2) Ribosomal protection

Question 31

What is Tigecycline used for?

Answer 31

* Broad-spectrum* 1) MRSA 2) MDR Enterococci 3) VRE 4) ESBL 5) Community-acquired pneumonia

Question 32

What is Minocycline used for?

Answer 32

RTI caused by H.influenzae Klebseilla spp Plague due to Yernia Pestis

Question 33

How is Tigecycline administered?

Answer 33

IV

Question 34

Use of Streptomycin

Answer 34

1) Enterococcal carditis (Gentamicin-resistant) | 2) M.TB/Other mycobacterial diseases

Question 35

Contraindications for Aminoglycosides

Answer 35

- Pregnancy - Renal impairment - Myasthenia gravis - Hearing defects

Question 36

Use of Gentamicin

Answer 36

``` More Gram (+) (+) Penicillin: Enterococcal endocarditis, Proteus, Pseudomonas, Klebsiella (+) Ceftriaxone: Staph endocarditis ```

Question 37

MOA of Macrolides

Answer 37

Binds reversibly to 50s subunit -> Inhibits protein synthesis (Bacteriostatic)

Question 38

Which of the bacterial protein synthesis inhibitors are cleared hepatically?

Answer 38

Macrolides, Clindamycin

Question 39

How is Clindamycin administered?

Answer 39

Oral/IV

Question 40

How is Linezolid administered?

Answer 40

Oral/IV

Question 41

Contraindications of Linezolid

Answer 41

- Pregnancy - Catheter-related infections - Not to be used within 2 weeks of MAO inhibitors