Inhibitors of protein synthesis Flashcards
Protein synthesis must continue even when cells are dormant. True or false?
True
Which drug is biosynthesised from acetate by several species of streptomyces?
Tetracycline
Tetracycline binding to nucleic acid inhibits cellular function. True or false?
False - only ribosome binding does
Tetracycline is contraindicated in children. Why?
Stain tooth enamel
Oxytetracycline is used to treat conjunctivitis in cats. True or false?
False - used to treat acne
Which tetracycline is used to treat lyme disease?
Demeclocycline
Which tetracycline is an antibacterial also used in prophylaxis of malaria?
Doxycycline
Minocycline is broader spectrum than other tetracyclines and can treat Neisseria meningitidis. True or false?
True
Streptomycin, gentamycin, kanamycin and neomycin belong to which group of drugs?
Aminoglycosides
Which ribosomal subunit does streptomycin bind?
30S
Aminoglycosides are active against gram negative bacteria. True or false?
True
Aminoglycosides show nephrotoxicity. True or false?
True
Gentamicin is derived from streptomyces. True or false?
False - derived from micromonospora
Which aminoglycoside binds to both ribosomal subunits, preventing them combining?
Tobramycin
Amikacin is arrived from which other aminoglycoside?
kanamycin
Paramomycin is used to treat a protozoal infection. Which ribosomal subunit does is interact with?
30S
What is the name of the only clinically available oxazolidinone?
Linezolid
Linezolid is not active against MRSA. True or false?
False
Linezolid is used against hospital acquired gram positive infections. True or false?
True
Which ribosomal subunit does linezolid bind to?
50S
Linezolid is toxic to mitochondria. True or false?
True
What is the soil bacterium that produces erythromycin?
Saccharopolyspora erythraea
Structure of erythromycin A is based on proprionate. True or false?
True
In what way are the structures of erythromycin and tetracycline similar?
both polyketides
Erythromycin is a macrolide. True or false?
True
Macrolides are first-line treatment in patients that are allergic to ______
penicillin
Macrolides are gut motilide agonists. What is meant by this?
Sensitised patients find that erythromycin and food do not sit well - taste and bitter is foul and cannot be masked
Macrolides give rise to a number of DDI. What is the reason for this?
They are metabolised by CYP450 3A4 in the liver
What is the mode of action of erythromycin?
Blocks protein synthesis after several rounds and oligopeptides are released from the ribosome.
It blocks the exit tunnel of the bacterial ribosome
What is the paediatric erythromycin that is used called and how does it work?
Erythromycin ethyl succinate - taste-free prodrug which hydrolyses in the blood.
Paediatric erythromycin needs to be stored in the fridge. True or false?
True - hydrolyses in the bottle
Are second generation macrolides more or less stable than erythromycin A?
More stable - so better in the stomach
Second generation macrolides are more hydrophilic than erythromycin A. True or false?
False - more hydrophobic
What is the half life of clarithromycin at pH 2.5 and 37 degrees?
310 mins
What is the half life of erythromycin at pH 2.5 and 37 degrees?
<10 mins
What is the only ketolide that is clinically used at the moment?
Telithromycin
What are some mechanisms of macrolide resistance?
Modification of ribosomal proteins
Efflux pumps, pumping macrolides out of cell
Methylation of adenine 2058 in 23S RNA
Chloramphenicol is only used to treat gram positive bacteria. True or false?
False - gram positive and gram negative
How many chiral centres does chloramphenicol have?
2 - but only one is active
Why is chloramphenicol not usually given internally and how is it mainly given?
Because it can cause aplastic anaemia.
It is typically found in eye drops
Of the four possible stereoisomers of chloramphenicol, how many are active?
One
Lincomycin is a natural product. True or false?
True
How is resistance to lincomycin and clindamycin induced?
Methylation of adenine 2058 in 23S RNA - so assumed that mode of action is similar to macrolides
Clindamycin is generally superior to lincomycin. True or false?
True
Clindamycin can be used to treat both aerobic and anaerobic infections. True or false?
True
Clindamycin is used in the treatment of toxic shock syndrome, often in combination with ________
vancomycin
Fusidic acid is a fungal product. True or false?
True
Fusidic acid is used to treat gram negative infections. True or false?
False - gram positive
Fusidic acid is most commonly seen in eye drops. It cannot be given as tablets. True or false?
False - can be given as tablets
What is the mode of action of fusidic acid?
Binds to EFG.GTP
the ternary complex binds to ribosome as normal
GTP is hydrolysed EFG.GDP is unable to leave the ribosome and protein synthesis is therefore stalled