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Mechanism of Drug Action (Drugs) > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

What are the mechanisms of antibiotic action?

A
  1. Inhibition of cell wall synthesis
  2. Disruption of membrane
  3. Inhibition of folic acid synthesis
  4. Inhibition of protein synthesis
  5. Inhibition of DNA replication/repair/transcription
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2
Q

What are the major antibiotics that inhibit cell wall biosynthesis?

A
  • β-lactam antibiotics
  • Vancomycin
  • D-cycloserine
  • Fosfomycin
  • Bacitracin
  • Isoniazid
  • Extended spectrum cephalosporin
  • Teixobactin
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3
Q

What are the β-lactam antibiotics?

A
  • Penicillin
  • Ampicillin
  • Amoxicilin
  • Methicillin
  • Extended spectrum cephalosporin
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4
Q

What is the mechanism of action of β-lactam antibiotics?

A

Inhibits the action of pepidoglycan transpeptidase by acting as a pseudosubstrate which is very slow to hydrolyse.

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5
Q

What is the mechanism of action of D-cycloserine?

A
  • Structural analogue of D-Ala.
  • Inhibits action of:
    1. L-Ala racemase
    2. D-Ala-D-Ala synthetase
    3. D-Ala-D-Ala muramyl tripeptide ligase
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6
Q

What is the mechanism of action of fosfomycin?

A

Inhibits action of pyruvyl transferase (converts NAG to NAM).

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7
Q

What is the mechanism of action of bacitracin?

A

Forms tight complex with Mg2+ and bactoprenol pyrophosphate and thus inhibits its action.

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8
Q

What is the mechanism of action of vancomycin?

A

Binds to D-Ala-D-Ala and inhibits cross-link formation.

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9
Q

What is the mechanism of action of isoniazid?

A

Inhibits synthesis of mycolic acids in cell envelope of M. tuberculosis.

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10
Q

What is the mechanism of action of teixobactin?

A

Binds to lipid II in peptidoglycan synthesis pathway and so inhibits synthesis of peptidoglycans.

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11
Q

What are the major antibiotics that inhibit/alter protein synthesis?

A
  • Chloramphenicol
  • Tetracycline
  • Macrolides
  • Fusidic acid
  • Aminoglycoside antibiotics
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12
Q

What are the antibiotics that act on 30S subunit of bacterial ribosomes?

A
  1. Tetracyclines
  2. Spectinomycin
  3. Aminoglycosides
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13
Q

What are the antibiotics that act on the 50S subunits of bacterial ribosomes?

A
  1. Chloamphenicol
  2. Lincosamides
  3. Linezolid
  4. Macrolides
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14
Q

What is the mechanism of action of chloramphenicol?

A

Blocks binding of aminoacyl-tRNA to 50S subunit of ribosomes.

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15
Q

What is the specificity of chloramphenicol?

A

Broad spectrum

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16
Q

What is the mechanism of action of tetracyclines?

A

Binds to 16S rRNA in 30S subunit of ribosomes and inhibits polypeptide synthesis by blocking entry of aminoacyl-tRNA into A-site on ribosome.

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17
Q

What are examples of tetracyclines?

A

Minocyclin

Doxycyclin

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18
Q

What is the specificity of tetracyclines?

A

Broad spectrum

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19
Q

What is the mechanism of action of macrolides?

A

Binds to 23S rRNA in 50S subunit of ribosomes and blocks polypeptide exit tunnel.

20
Q

What are examples of macrolides?

A

Erythromycin

Clathrinomycin

Azithromycin

Tylosin

21
Q

What is the specificity of macrolides?

A

Narrow spectrum (Gram +ve)

22
Q

What is the mechanism of action of fusidic acid?

A

Inhibits action of elongation factor G, thus inhibiting movement of 30S subunit along mRNA during translation.

23
Q

What is the specificity of fusidic acid?

A

Narrow spectrum (Gram +ve)

24
Q

What is the mechanism of action of aminoglycosides?

A
  • In uninitiated state, these antibiotics freeze the met-tRNA pre-initiation complex on the 30S subunit, preventing initiation and peptide synthesis.
  • In initiated state, they bind to 30S subunit and decreases the fidelity of ribosomes, causing mistakes to be made in reading of mRNA.
25
Q

What are the aminoglycoside antibiotics?

A
  • Streptomycin
  • Gentamycin
26
Q

What is the specificity of aminoglycosides?

A

Narrow spectrum (Gram +ve)

27
Q

What is the mechanism of action of lincosamides?

A

Binds to 23S RNA of 50S subunit and interacts with P- and A-sites. Acts as competitive inhibitor for aminoacyl-tRNA and peptidyl-tRNA at these positions.

28
Q

What are examples of lincosamides?

A
  1. Lincomycin
  2. Clindamycin
29
Q

What are the major antibiotics that inhibit DNA replication/repair/transcription?

A
  • Fluoroquinolones
  • Rifampin
  • Daunomycin
  • Bleomycin
  • Mitomycin
30
Q

What is the mechanism of action of fluoroquinolones?

A

Inhibits action of type II topoisomerase DNA gyrase, possibly by binding to ATP binding site and inhibitng ATP entry.

31
Q

What are the fluoroquinolones?

A
  • Ciprofloxacin
  • Levofloxacin
32
Q

What is the specificity of quinolones?

A

Broad spectrum

33
Q

What is the mechanism of action of rifampin?

A

Binds to β-subunit of DNA-dependent RNA polymerase and blocks exit of RNA chain during transcription.

34
Q

What is the clinical use of rifampin?

A

Mycobacteria (e.g. TB)

35
Q

What is the mechanism of action of daunomycin?

A

Intercalates into dsRNA and causes unwinding of double helix and inhibits DNA replication and transcription.

36
Q

What is the mechanism of action of bleomycin?

A

Chelates Fe ions and generates superoxide and hydroxyl radicals that cause DNA damage.

37
Q

What is the mechanism of action of mitomycin C?

A

Alkylates and cross-links DNA double strand. This inhibits DNA replication and transcription.

38
Q

What are the major antibiotics that inhibit folic acid synthesis?

A
  • Sulfamethoxazole
  • Trimethoprim
  • Co-trimoxazole
39
Q

What is the mechanism of action of sulfamethoxazole?

A

Inhibits action of dihydropteroate synthase (DHPS) in tetrahydrofolate synthesis.

40
Q

What is the mechanism of action of trimethoprim?

A

Inhibits action of dihydrofolate reductase in tetrahydrofolate synthesis.

41
Q

What is the mechanism of action of co-trimoxazole?

A

Combination of sulfamethoxazole and trimethoprim.

42
Q

What are the major antibiotics that disrupt cell membranes?

A
  • Valinomycin
  • Gramicidin A
  • Polymixins
43
Q

What is the mechanism of action of valinomycin?

A

Facilitates K+ diffusion across membrane and disrupts K+ gradient.

44
Q

What is the mechanism of action of gramicidin A?

A
  • Dimerisation allows formation of ion channel allowing H+ in particular to cross membranes.
  • Disrupts [H+] gradient. Reduces ATP synthesis and also disrupts function of many H+-dependent co-transporters.
45
Q

What is the mechanism of action of polymixin?

A
  • Integrates into cell membrane and interacts with constituent phospholipids.
  • Causes aggregation of lipids into ‘micelle-like aggregations’ and disrupts membrane permeability.

Mechanism of Drug Action (Drugs) (26 decks)

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