Antibacterial Antibiotics

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Anonymous
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14115
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Antibacterial Antibiotics
Updated:
2010-04-12 17:11:04
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Medchem
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antibacterial antibiotics
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  1. Antibiotic
    • Product of metabolism
    • synthetic product produced as a structural analog of a naturally occurring compound
    • antagonizes growth of microorganisms
    • effective in low concentrations
    • selective toxicity
    • sufficient chemical stability
    • elimination of the antibiotic must be slow to allow a convenient dosing schedule
  2. Antibiotics in feed
    increase meat production in many animals
  3. Commercial production of antibiotics (6)
    • isolation of pure culture of antibiotic producing organism
    • fermentation
    • isolation of the antibiotic from culture medium
    • purification
    • assay for potency, sterility...
    • formulation into acceptable and stable dosage form
  4. Mechanisms of Action
    • Interfere with cell wall biosynthesis
    • Interfere with microbial protein synthesis
    • Interfere with Nucleic Acid synthesis
  5. Cell Wall Biosynthesis Inhibitors
    Bacteriocidal
  6. Protein Biosynthesis Inhibitors
    Bacteriostatic except aminoglycosides
  7. Nosocomial
    hospital acquired
  8. B-Lactam Antibiotics
    • Gram + Bacteria
    • -Cidal Action with low toxicity
  9. MoA of B-Lactams
    • inhibition of bacterial cell wall synthesis
    • Acylate active site serine in Penicillin binding proteins
  10. 1 Oxford Unit
    amount of PCN that will inhibit the growth of a strain of staph in 50mL of culture medium
  11. 1 Unit Pure PCN
    0.6 mcg PCN G
  12. USP Numbering System
    • N=1
    • S=4
  13. Chemical stability of B-Lactams
    • lactam ring sensitive to acidic conditions
    • Oxidizing agents inactivate PCN by oxidizing the S atom
    • Prolonged heating will inactivate
    • e- withdrawing group added = increased stability
  14. PCN Allergy
    • caused by formation of antigenic penicilloyl proteins formed in vivo by the reaction of nucleophillic groups on specific proteins with B-lactam carbonyl group
    • #1 problem with PCNs
    • between 1-10% of population
  15. PCN Resistance (4)
    • B-Lactamase
    • decreased permeability (esp. in G-)
    • Intrinsic Resistance (affinity of PBP for PCN)
    • Tolerance (bacteria sense B-Lactam and stop growth to prevent lysis)
    • Methicillin
    • steric hinderance
  16. Increase activity against gram negative bacilli
    • ionized or polar group into a-position
    • Increased hydrophilicity to pass through pores in cell membrane
    • also more oral bioavailability
  17. Ampicillin***
  18. Carbenicillin***(3)
    • pseudomonas
    • klebsielia
    • Non-toxic, ionized at phys pH
  19. PCN and Aminoglycosides
    • incompatible, both will inactivate
    • good combo therapy
  20. Penicillin G***
  21. Amoxicillin
    • Piperacillin
    • acyl urido substituent
  22. Class I B-Lactamase inhibitors
    • clavulanic acid
    • sulbactam
    • tazobactam
    • suicide substrates
  23. Class II B-lactamase inhibitors
    • "slow" Substrates
    • carbapenemsm (imipenem)
  24. Clavulanate***
    • Imipenam
    • destroyed in kidney if administered alone
    • cilastatin inhibits DHP1
  25. Cephalosporins
    • similar to PCN but have a 6 membered ring rather than 5 attached to B-Lactam
    • slightly more stable than PCNs
  26. Oral Cephalosporins
    • increased acid stability of lactam ring resulting from presence of protonated amino group on 7-acylamino portion of molecule
    • absence of leaving group in 3 position
  27. Cephalosporin spectrum
    • broad spectrum
    • more resistant to B-lactamase (esp. G+)
  28. Cephalosporin B-Latamase Resistance
    • Increased by 7-methoxyl substituent
    • Increased by alkoximino in aminoacyl group
  29. Adverse reactions and Drug Interactions of Cephalosporins
    • #1: Allergic Reaction (3-7% allergic to both Cephs and PCNs)
    • Cephalosporins with N-methyl 5-thiotetrazole (MTT) at 3 position increase incidence of hypoprothrombinemia due to inhibition of Vit. K requiring enzymes
    • Treat with Vit. K
    • MTT group also causes intolerance to alcohol
  30. Cephalexin***
    • Homolog of Ampicillin
    • Cefadroxil
    • Homolog of amoxicillin
  31. Monobactams
    • Single ring system
    • Aztreonam
    • Aztreonam
    • G- Bacteria
  32. Aminoglycosides (4)
    • Oto- and nephrotoxicity
    • not distributed to CNS, Bone, fatty or connective tissues
    • aerobic gram-negative bacilli
    • act on bacterial ribosome to inhibit protein synthesis and interfere with fidelity of translation
  33. Aminoglycoside Resistance Mechanisms (3)
    • acetylating
    • phosphorylating
    • adenylylating
  34. Tetracylines (5)
    • broad spectrum
    • amphoteric compounds
    • Strong acids and bases will inactivate
    • di-tri-valent metals will form a complex and inhibit absorption
    • bacteriostatic
  35. Three biochemically distinct mechanisms of resistance to tetracyclines
    • 1. Efflux
    • 2. Ribosomal protection
    • 3. Enzymatic oxidation
  36. Macrolides
    • Inhibitors of protein biosynthesis
    • Bacteriostatic
    • 1. large lactone ring
    • 2. ketone group
    • 3. glycosidically linked amino sugar
  37. Macrolide Spectrum of Activity
    • generally effective agains most G+
    • some G- cocci (neisseria)
    • mycoplasma
    • chlamydia
    • campylobacter
    • legionella
  38. Erythromycin
  39. Lincomycins
    • Sulfur containing antibiotics
    • resemble macrolides in spectrum
    • static or cidal
    • clindamycin
  40. Clindamycin
  41. Polypeptides
    • Renal toxicity
    • Vancomycin
    • 1. several strucurally similar entities
    • 2. most are cyclic
    • 3. frequently contain D-amino acids
    • 4. many contain non-amino acid moities
  42. Bacitracin and Vancomycin
    • Interfere with cell wall synthesis
    • effective only against Gram +
  43. Gramicidins and polymyxins
    interfere with cell membrane functions
    • Vancomycin
    • Binds to D-Ala, D-Ala terminus
    • Resistance if D-Ala, D-Lac
    • Chloramphenicol
    • First broad spectrum antibiotic
    • inhibits protein synthesis
    • synthetic
  44. Novobiocin
    inhibitor of DNA gyrase

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