PHRD5915 Drug Design Lecture 11 - Pathogen Drug Targets: Bacteria and Fungi

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PHRD5915 Drug Design Lecture 11 - Pathogen Drug Targets: Bacteria and Fungi
2014-05-12 05:32:58
Pathogen Drug Targets

Pathogen Drug Targets Bacteria and Fungi
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  1. average mutation rate for bacteria
  2. transformation
    donor bacterium dies & fragments of the genome are picked up by the recipient
  3. transduction
    viruses (bacteriophages) pick up a piece of the genome  by accident & insert it into the recipient upon infection
  4. conjugation
    (bacterial sex) donor & recipient form a physical bridge between cytoplasms & F plasmid is copied & transferred to recipient
  5. F plasmid
    bacterial fertility factor that expresses all the genes necessary for sexual conjugation
  6. 5 mechanisms of bacterial resistance
    • 1) altered drug target
    • 2) eliminated drug target
    • 3) restrict access or pump out abx
    • 4) express inactivating enzyme
    • 5) produce access restricting biofilm
    • 6) enter state of quiescence
  7. target of -lactam ring abx
    penicillin binding proteins (PBP's)
  8. cell wall permeable to small molecules
  9. cell wall w/ external membrane containing pumps
  10. allows bacterial to create rigidity & maintain shape in many different osmolar environments
    cross-linked peptidoglycans
  11. proteins that build & repair the bacterial cell wall
  12. PBP-1
    transamidase that crosslinks peptidoglycan strands
  13. penicillin MOA
    takes place of D-ala-D-ala in PBP-1 active site -> when tried to convert it, -lactam ring breaks & attaches permanently to enzyme
  14. major form of resistance for -lactam ring abx
    ability of bacteria to express an enzyme that cleaves the ring (-lactamases)
  15. functional group that determines the specific type of penicillin
    side chain at C6
  16. type of penicillin that is more acid stable
    Penicillin V
  17. Augmentin MOA
    • amoxicillin is a broad spectrum penicillin
    • clavulanic acid inhibits -lactamases
  18. major reason 6-8% of the US pop is allergic to penicillins
    they can form haptens
  19. MOA of synthetic antimicrobials (sulfonamides, trimethoprim, quinolones, nitroheteroaromatics)
    inhibit various aspects of nucleic acid (RNA & DNA) biosynthesis & fcn
  20. sulfonamide MOA
    inhibitor of dihydropteroate synthase to affect bacterial DNA synthesis pathway
  21. quinolone MOA
    inhibitor of bacterial DNA gyrase & Topo IV
  22. these compounds need to be activated by an enzyme unique to anaerobic organisms to fcn
    nitroheteroaromatic compounds
  23. examples of protein synthesis inhibitors (2)
    • gentamycin
    • erythromycin
  24. MOA of protein synthesis inhibitors
    bind to bacterial ribosomal subunits to block translation & incorporate incorrect amino acids
  25. serious potential side effects of animoglycosides (protein synthesis inhibitor)
    • destruction of cells in the ear required for balance
    • necrosis of kidney tubules
  26. considered some of the safest of the abx
    macrolides (protein synthesis inhibitor)
  27. bacterial cyclic peptide MOA
    inhibit cell wall synthesis
  28. examples of bacterial cyclic peptides (2)
    • vancomycin
    • daptomycin
  29. constructed from amino acids by enzyme complexes & contain both normal and modified animo acids
    bacterial cyclic peptides
  30. vancomycin MOA
    binds D-ala-D-ala terminals of peptidoglycan & blocks PBP from crosslinking peptidogylcan strands
  31. what have vancomycin-resistant bacteria substituted D-ala-D-ala with?
  32. penicillin vs vancomycin
    • penicillin inhibits the enzyme
    • vancomycin masks the substrate
  33. polyene MOA
    insert into the ergosterol-containing membrane, rendering it leaky
  34. examples of polyenes
    • amphotericin B
    • Nystatin
  35. ring structures (macrocyclic lactones) w/ distinct hydrophilic & hydrophobic regions
  36. azole MOA
    inhibit essential enzyme in the ergosterol biosynthetic pathway (14 demethylase)