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Term 4: Infectious Diseases > Antimicrobial Agents > Flashcards

Antimicrobial Agents Flashcards

1
Q

What enzyme do B-lactams inhibit, and what does it do?

A
  • blocks transpeptidase
  • normally cross-links Muramic acid via their D-ala-D-ala portions (peptidoglycans)
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2
Q

What, on bacteria, does penicillin look like?

A

D-ala-D-ala

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3
Q

TEM

A

B-lactamase

TEM TEM TEM

TEM TEM

TEM

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4
Q

What are the glycopeptide antimicrobials?

A
  • Vancomycin
  • teicoplanin
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5
Q

What type of bacteria are intrinsically resistant to Vancomycin?

A

Gram (-) bacteria

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6
Q

What does Vancomycin bind to?

A

D-ala-D-ala

-Blocks cross-linking reaction

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7
Q

What is the phenotype of vancomycin resistance?

A

D-ala-D-ala → D-ala-D-lac

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8
Q

What is Vancomycin Intermediate S. aureus (VISA)?

A
  • Characterized by thickening of cell wall.
  • Thicker cell wall has more D-ala-D-ala in outer layer of peptidoglycan which can trap vancomycin.
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9
Q

What is cycloserine?

A
  • cell wall synthesis inhibitor
  • blocks D-ala ligase

*needs to enter cytoplasm

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10
Q

Which antibiotics inhibits the 30s segment of bacterial ribosomes?

A
  • Aminoglycosides
  • Tetracyclines
  • Tigecycline
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11
Q

How do aminoglycosides work?

A

-Bind to 30 S subunit of ribosome and prevent formation of initiation complex

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12
Q

How is bacterial resistance to aminoglycocides mediated?

A
  • Enzymatic inactivation of the drug
  • A set of plasmid encoded enzymes can adenylate, phosphorylate or acetylate aminoglycosides
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13
Q

How do tetracyclines work?

A

Attach to 30 S subunit to prevent binding of incoming aminoacyl-tRNA

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14
Q

How is bacterial resistance to tetracyclines work?

A
  • active efflux of the drug out of the bacteria
  • also by a plasmid-encoded tetracycline binding protein
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15
Q

How do macrolides work?

A

Bind 50S subunit and block translocation.

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16
Q

How do lincosamides work?

A

Bind 50S subunit and block translocation.

17
Q

What classes of antibiotics bind the 50s subunit of bacterial ribososmes?

A
  • Macrolides
  • Lincosamides
  • spectinomycin
  • Chloramphenicol
  • oxazolidinomes
18
Q

What is the bacterial mechanism for resistance to macrolides and lincosamides?

A

-altered target site

19
Q

How does chloramphenicol work?

A
  • binds 50s subunit of ribosome
  • inhibits peptidyl transferase to block peptide bond formation
20
Q

What is the bacterial mechanism of resistance to chloramphenicol?

A

-enzymatic inactivation

21
Q

How do oxazolidinones work?

A

-Binds 50S subunit and prevents association with 30S subunit

22
Q

What antibiotic classes inhibit bacterial folic acid metabolism?

A
  • Sulfonamides
  • Trimethoprim
23
Q

How do sulfonamides work?

A
  • inhibit bacterial purine/pryimidine synthesis
  • blocks dihydropteroate synthetase
24
Q

How does trimethoprim work?

A
  • inhibits bacterial purine/pyrimidine synthesis
  • inhibits DHFR
25
Q

How is bacterial resistance of sulfonamides mediated?

A

By pass the blocked pathway

26
Q

How is bacterial resistance of trimethoprim mediated?

A

Bypass the blocked pathway

27
Q

What class of antibiotics are nucleic acid synthesis inhibitors?

A
  • Quinolones
  • Rifampicin
28
Q

How do quinolones work?

A

-block DNA gyrase

& topoisomerase IV

29
Q

How is bacterial resistance to quinolones mediated?

A
  • mutations in gyrase and topo IV genes is the most common mechanism of resistance
  • Efflux
  • Qnr produced and binds/protects DNA gyrase
30
Q

How does rifampicin work?

A

Blocks beta-subunit of the bacterial RNA polymerase enzyme

31
Q

How is bacterial resistance to rifampicin mediated?

A

mutations in the gene for the beta-subunit of RNA Polymerase

32
Q

What antibiotics work via bacterial membrane disruption?

A
  • Polymixins
  • Daptomycin
33
Q

How do polymixins work?

A

-act like a detergent and disrupt cytoplasmic membrane

*used topically due to toxicity

*resistance is rare

34
Q

How does Daptomycin work?

A
  • dysrupts cell membrane
  • Depolarizes bacteria resulting in bacterial death from release of intracellular ions
35
Q

Combinations of penicillins and ____________ because penicillins allow increased passage of __________.

A

aminoglycosides

Term 4: Infectious Diseases (21 decks)

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