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233 FINAL > Antimicrobial 2: Agents that Target Bacterial Protein Synthesis > Flashcards

Antimicrobial 2: Agents that Target Bacterial Protein Synthesis Flashcards

1
Q

Antibiotics Targeting Protein Synthesis

Antibiotics/ antimicrobials that inhibit protein synthesis and are primarily bacteriostatic include drugs in the which classes?

A
  • Tetracyclines
  • Aminoglycosides
  • Macrolides
  • Chloramphenicol
  • Oxazolidinones
  • Fusidic Acid
  • Streptogramins
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2
Q

Protein Synthesis

Describe the steps in Protein Synthesis:

A

DNA –> (transcription) –> RNA –> mRNA –> (translation) –> protein

(see slide 5 picture for details)

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3
Q

Bacterial Ribosome

what are the components?

A

See slide 6 picture

50S: 2 ribosomal rRNA (5S rRNA, 23S rRNA)
30S: 16S rRNA

forms 70S complex

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4
Q

Tetracyclines (bacteriostatic)

Drugs

See slide 7 for molecular structure.

A
  • Tetracycline
  • Oxytetracycline
  • Demeclocycline
  • Doxycycline
  • Minocycline - BEST FOR CNS
  • Tigecycline

bacteriostatic

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5
Q

Tetracyclines (bacteriostatic)

Effective against gram-positive & gram-negative bacteria:

A

Mycoplasma
Rickettsia
Chlamydia
Also effective against protozoa

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6
Q

Tetracyclines (bacteriostatic)

MOA

A
  • Are taken up into susceptible organisms by active
    transport and inhibit protein synthesis
  • Tetracyclines bind reversibly to the 16S subunit of the
    30S ribosomal subunit and inhibit translation
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7
Q

Tetracyclines (bacteriostatic)

AE

A
    • Staining of teeth & dental hypoplasia
    • Bone deformities
      Chelating calcium: stay in deposits of bones and teeth
  • GI disturbances (initially via direct irritation and
    followed by modification of the gut flora)
  • Vitamin B complex deficiency
  • Hepatotoxicity
  • Phototoxicity (demeclocycline)
  • Vestibular disturbances (minocycline)
  • Anti-anabolic actions in the host Bone marrow
    depression

**Contraindicated in pregnant women, nursing mothers and children

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8
Q

Aminoglycosides (bactericidal in high doses & bacteriostatic)

Drugs

See slide 10 for molecular structure.

A
  • Gentamicin
  • Streptomycin
  • Amikacin
  • Tobramycin
  • Neomycin
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9
Q

Aminoglycosides (bactericidal & bacteriostatic)

Characteristics

A
  • Are more effective against gram-negative bacteria
  • Their penetration through the cell membrane
    depends on oxygen-dependent active transport
    (minimal action against anaerobic bacteria)
  • Have both bacteriostatic and bactericidal actions
  • Amikacin was designed as a poor substrate for
    microbial enzymes that inactivate aminoglycosides
    (to counteract aminoglycoside resistance)
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10
Q

Aminoglycosides (bactericidal & bacteriostatic)

MOA

A
  • Bind irreversibly to the 30S ribosomal subunit and
    inhibit protein synthesis (trap ribosomes at the AUG
    start codon)
  • As cationic molecules they create fissures and pores
    in the outer cell membrane, causing leakage of
    intracellular contents and enhancing antibiotic
    uptake
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11
Q

Aminoglycosides (bactericidal & bacteriostatic)

AE

A
    • Ototoxicity
    • Nephrotoxicity
    • Paralysis via neuromuscular blockade (rare)
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12
Q

Macrolides (bacteriostatic)

Drugs

See slide 13 for molecular structure.

A

• Macrolides are lactone rings attached to deoxysugars
and include the following:

  • Erythromycin
  • Clarithromycin
  • Azithromycin
  • Telithromycin
  • Have similar antimicrobial spectrum to that of
    Penicillins, and are thus safe alternatives for
    individuals showing hypersensitivity to penicillins

bacteriostatic

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13
Q

Macrolides (bacteriostatic)

MOA

SIGNIFICANT CYP450 INHIBITORS

A
  • Bind the 23S rRNA molecule of the 50S ribosomal
    subunit and inhibit peptidyl transferase (block transfer of new amino acids onto the growing peptide chain)

Blocks the exit channel

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14
Q

Macrolides (bacteriostatic)

AE

A
    • Cholestatic jaundice (treatment > 2 wks)
      bile can’t flow from liver to duodenum
  • GI disturbances
  • Hypersensitivity reactions (rash and fever)
  • Transient hearing disturbances
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15
Q

Chloramphenicol (bacteriostatic)

Characteristics

See slide 16 for molecular structure

A
  • Chloramphenicol was originally isolated from cultures
    of Streptomyces
- Is bacteriostatic against Gram-negative and Gram- 
  positive organisms and should be reserved for serious 
   infections Meningitis (when penicillin cannot be used)
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16
Q

Chloramphenicol (bacteriostatic)

MOA

A
  • (same as macrolides) bind the 23S rRNA molecule of
    the 50S ribosomal subunit and inhibit peptidyl
    transferase (block transfer of new amino acids onto
    the growing peptide chain)
17
Q

Chloramphenicol (bacteriostatic)

AE

A
    • ‘grey baby’ syndrome, grey colour of skin, vomiting, diarrhea, mortality
  • Severe depression of bone marrow causing
    • pancytopenia, decrease in all blood cells
18
Q

Oxazolidinedione (bacteriostatic)

Consider the first truly new class of antibacterials to reach the market -

Drug

See slide 18 for molecular structure

A

Linezolid

19
Q

Oxazolidinedione (bacteriostatic)

Charactistics

A
  • Active against wide variety of Gram-positive bacteria
    and useful against drug-resistant bacteria such as
    MRSA
20
Q

Oxazolidinedione (bacteriostatic)

MOA

A
  • Inhibit bacterial protein synthesis via a novel
    mechanism involving antagonism of the N-
    formylmethionyl-tRNA binding to the 70S ribosome
21
Q

Oxazolidinedione (bacteriostatic)

PK?

A
  • Linezolid has 100% oral bioavailability

- Linezolid is also a weak monoamine oxidase inhibitor

22
Q

Oxazolidinedione (bacteriostatic)

AE

A
    • Thrombocytopenia
    • Serotonin syndrome
    • Hyperlactatemia
  • Diarrhea
  • Nausea
  • Rash
  • Dizziness
23
Q

Other Agents Targeting Protein Synthesis

Fusidic Acid (bacteriostatic)

MOA

See slide 21 for molecular structure

A
  • Steroid antibiotic against Gram-positive bacteria that
    inhibits bacterial protein synthesis by interfering with translation
  • steroid backbone
24
Q

Other Agents Targeting Protein Synthesis

Fusidic Acid

AE

A
    • Jaundice

- GI disturbances

25
Q

Other Agents Targeting Protein Synthesis

Streptogramins (Quinupristin & Dalfopristin) -

(bacteriostatic)

MOA

See slide 22 for molecular structure

A
  • Cyclic peptides that inhibit bacterial protein synthesis
    by binding to the 50S subunit of the bacterial ribosome
    (Gram-positive organisms)
26
Q

Other Agents Targeting Protein Synthesis
Streptogramins (Quinupristin & Dalfopristin) -

(bacteriostatic)

AE

A
  • Inflammation at infusion site (*arthralgia and *myalgia)

- Nausea, vomiting & diarrhea

27
Q

Other Agents Targeting Protein Synthesis

Clindamycin (a lincosamide) - (bacteriostatic)

MOA

See slide 23 for molecular structure

A
  • Same as macrolides & chloramphenicol
  • Inhibit bacterial protein synthesis
  • Bind the 23S rRNA molecule of the 50S ribosomal
    subunit and inhibit peptidyl transferase (block transfer
    of new amino acids onto the growing peptide chain)
28
Q

Other Agents Targeting Protein Synthesis

Clindamycin (a lincosamide) - (bacteriostatic)

AE

A
    • Potentially lethal psuedomembranous colitis (toxin-
      forming C. difficile)
  • GI disturbances (uncomfortable diarrhea)
29
Q

Quinolones (Bactericidal)

Drugs

Effective against both Gram-positive & Gram-negative bacteria

See slide 24 for molecular structure

A 
Quinolones are broad-spectrum fluorinated) and include;
• Nalidixic Acid
• Ciprofloxacin
• Levofloxacin
• Ofloxacin
• Norfloxacin
• Moxifloxacin

good for UTI

30
Q

Quinolones (Bactericidal)

MOA

A
  • Inhibit topoisomerase II (bacterial DNA gyrase which cuts open DNA and reseals it) and topoisomerase IV
  • Prevent negative supercoiling of DNA (required to
    allow transcription or replication of DNA) by DNA
    gyrase.
  • Prevent topoisomerase IV mediated decatenation of
    daughter DNA molecules.
31
Q

Quinolones (Bactericidal)

AE

A
  • *Arthropathy
  • *Convulsions (can be exacerbated with concurrent use of theophyllines)
  • due to point mutations of DNA gyrase enzyme
  • high conc in kidneys for excretion
  • GI disturbances
  • Hypersensitivity reactions (rashes)
  • Headache and dizziness
32
Q

Summarize Antibacterials that interfere with bacterial protein synthesis : (6)

A
  • Tetracyclines bind reversibly to the 16S subunit of the
    30S ribosomal subunit and inhibit translation
  • Aminoglycosides bind irreversibly to the 30S ribosomal
    subunit and inhibit protein synthesis (trap ribosomes at
    the AUG start codon)
  • Macrolides bind the 23S rRNA molecule of the 50S
    ribosomal subunit and inhibit peptidyl transferase
    (block transfer or new amino acids onto the growing
    peptide chain)
  • Chloramphenicol & clindamycin have a similar
    mechanism of action as the macrolide antibiotics
  • Oxazolidinones are the newest class of antibacterials,
    which inhibit bacterial protein synthesis via a novel
    mechanism involving antagonism of the N-
    formylmethionyl-tRNA binding to the 70S ribosome
  • Quinolines, which inhibit topoisomerase II (bacterial
    DNA gyrase) and thereby prevent supercoiling of
    DNA, leading to cessation of transcription/replication
    of DNA
33
Q

why do antibiotics have hard time targeting G- bac ?

A
  • outer membrane makes it hard for drugs to reach bacterium

- outer membrane has porin channels that prevent entry of chemicals

233 FINAL (15 decks)

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