Antibiotics That Inhibit Protein Synthesis

Question 1

Which organelle is responsible for all protein synthesis in a cell?

Answer 1

Ribosome

Question 2

What percentage of the dry weight of a bacterial cell do ribosomes make up?

Answer 2

30%

Question 3

What are ribosomes made of?

Answer 3

55 proteins and 3 strands of RNA

Question 4

Why is protein synthesis a huge drug target?

Answer 4

Because it is always needed to sustain life

Question 5

How are tetracyclines synthesised?

Answer 5

They are biosynthesised from acetate by several species of streptomyces.

Question 6

How do tetracyclines inhibit protein synthesis?

Answer 6

By binding to ribosomes near the small protein subunit S10

Question 7

Why are tetracyclines contra indicated in children?

Answer 7

Because they stain growing tooth enamel

Question 8

Give two examples of aminoglycoside antibiotics

Answer 8

Gentamicin and streptomycin

Question 9

True or false, aminoglycosides have a very narrow therapeutic window?

Answer 9

True

Question 10

What is the mechanism of action of streptomycin?

Answer 10

It binds to 16S RNA in 30S ribosomal subunit so the binding of aminoacyl-tRNA is inhibited and the genetic code is misread

Question 11

Which aminoglycoside is inhaled by CF patients to treat infections?

Answer 11

Tobramycin

Question 12

True or false, linezolid is active against MRSA?

Answer 12

True

Question 13

Give a disadvantage of linezolid

Answer 13

It is toxic to mitochondria

Question 14

Which ribosomal subunit do the macrolides inhibit?

Answer 14

50s

Question 15

Which type of bacteria are the macrolides most active against?

Answer 15

Gram positive

Question 16

Which macrolide is used as first line treatment for penicillin allergic patients?

Answer 16

Erythromycin

Question 17

Give 3 problems associated with macrolides?

Answer 17

They are metabolised by the cytochrome P450 enzyme which gives rise to drug interactions, they can cause stomach upsets and their taste is bitter and foul

Question 18

What is the mechanism of action of erythromycin?

Answer 18

It blocks the exit tunnel of the bacterial ribosome in the 50s subunit

Question 19

What is erythromycin ethyl succinate and what is it used for?

Answer 19

It is a prodrug of erythromycin which is hydrolysed in the blood stream to erythromycin. It is used for paediatric patients as it is taste free.

Question 20

Give a disadvantage of erythromycin ethyl succinate

Answer 20

It is unstable so hydrolyses in the medicine bottle therefore it needs to be kept in the fridge

Question 21

Why is chloramphenicol not usually taken orally? Give an exception to this.

Answer 21

Because it can cause aplastic anaemia which is likely to kill. The only exception is in the treatment of typhoid as the benefits outweigh the risk

Question 22

Give two examples of lincosamides.

Answer 22

Clindamycin and lincomycin

Question 23

Which class of antibiotics has the same mechanism of action as the macrolides?

Answer 23

The lincosamides