Antibacterial antibiotics Mechanism of action - USMLE Forums
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  #1  
Old 01-07-2010
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Biochemistry Antibacterial antibiotics Mechanism of action

This is commonly asked in USMLE
Here's a quick review:

  • Macrolides and Clindamycin ----> blocking the trans-location step of translation (50S subunit); streptogramins may also work on the extrusion of the completed peptide.
  • Aminoglycosides ----> Prevent initiation complex by causing misreading of the mRNA code (30S subunit)
  • Chloremphenicol and cycloheximides ----> inhibit peptidyl transferase (50S subunit)
  • Tetracyclines, Streptogramins, and Linezolid ----> inhibit initiation complex formation by inhibiting the attachment of tRNA to the A site (30S subunit for tetracylin :50S subunit for streptogramins and linezolid)
  • Pencillins and cephalosporins ----> bind to PBP and inhibit transpeptidation of the cell wall
  • Flouroquinolones ----> inhibit topoisomeras II (DNA gyrase) and topoisomerase IV
  • Sulfonamides ----> blocking dihydropterate synthetase
  • Trimethoprim and pyrimethamine ----> blocks dihydrofolate reductase
  • Vancomycin ----> binds to D-Ala-D-Ala muramyl pentapeptide and halt transglycosylation of the peptidoglycan elongation in bacterial cell wall
  • Metronidazole ----> free radicals formation (needs oxygen to work)
  • Polymyxins ----> damages the membrane osmotic properties
  • INH ----> inhibit synthesis of mycolic acid
  • Rifampin ----> works on sigma factor needed for initiation of transcription
  • Ethambutol ----> inhibit synthesis of arabinogalactan a cell wall component of mycobacterium
  • Puromycin ----> attaches to A site and premature termination of translation
If you know of any high yield antibacterials to be added, please add to the list.
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  #2  
Old 01-07-2010
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This "theme" is so confusing and conflicting, you never get consistent information:

Tetracycline----> attaches to A site in 30s (Thirty) subunit, initiation and elongation inhibition
Linezolid: initiation inhibition through 50s
Streptogramins: as macrolides
Sulfonamides: blocking dihydropterate synthetase only, they act in synergism with Trimethoprim or Pyrimethamine which block DHF reductase.
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Old 01-08-2010
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Quote:
Originally Posted by DrSeddik View Post
This "theme" is so confusing and conflicting, you never get consistent information:

Tetracycline----> attaches to A site in 30s (Thirty) subunit, initiation and elongation inhibition
Linezolid: initiation inhibition through 50s
Streptogramins: as macrolides
Sulfonamides: blocking dihydropterate synthetase only, they act in synergism with Trimethoprim or Pyrimethamine which block DHF reductase.
Thanks DrSeddik, I edited the main post to reflect your notes
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