Antibiotics That Inhibit Protein Synthesis Flashcards
Which organelle is responsible for all protein synthesis in a cell?
Ribosome
What percentage of the dry weight of a bacterial cell do ribosomes make up?
30%
What are ribosomes made of?
55 proteins and 3 strands of RNA
Why is protein synthesis a huge drug target?
Because it is always needed to sustain life
How are tetracyclines synthesised?
They are biosynthesised from acetate by several species of streptomyces.
How do tetracyclines inhibit protein synthesis?
By binding to ribosomes near the small protein subunit S10
Why are tetracyclines contra indicated in children?
Because they stain growing tooth enamel
Give two examples of aminoglycoside antibiotics
Gentamicin and streptomycin
True or false, aminoglycosides have a very narrow therapeutic window?
True
What is the mechanism of action of streptomycin?
It binds to 16S RNA in 30S ribosomal subunit so the binding of aminoacyl-tRNA is inhibited and the genetic code is misread
Which aminoglycoside is inhaled by CF patients to treat infections?
Tobramycin
True or false, linezolid is active against MRSA?
True
Give a disadvantage of linezolid
It is toxic to mitochondria
Which ribosomal subunit do the macrolides inhibit?
50s
Which type of bacteria are the macrolides most active against?
Gram positive
Which macrolide is used as first line treatment for penicillin allergic patients?
Erythromycin
Give 3 problems associated with macrolides?
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
What is the mechanism of action of erythromycin?
It blocks the exit tunnel of the bacterial ribosome in the 50s subunit
What is erythromycin ethyl succinate and what is it used for?
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.
Give a disadvantage of erythromycin ethyl succinate
It is unstable so hydrolyses in the medicine bottle therefore it needs to be kept in the fridge
Why is chloramphenicol not usually taken orally? Give an exception to this.
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
Give two examples of lincosamides.
Clindamycin and lincomycin
Which class of antibiotics has the same mechanism of action as the macrolides?
The lincosamides
