Antimicrobial Agents Flashcards Preview

Term 4: Infectious Diseases > Antimicrobial Agents > Flashcards

Flashcards in Antimicrobial Agents Deck (35):
1

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

-blocks transpeptidase

-normally cross-links Muramic acid via their D-ala-D-ala portions (peptidoglycans)

2

What, on bacteria, does penicillin look like?

D-ala-D-ala

3

TEM

B-lactamase

TEM TEM TEM

TEM TEM

TEM

4

What are the glycopeptide antimicrobials?

-Vancomycin

-teicoplanin

5

What type of bacteria are intrinsically resistant to Vancomycin?

Gram (-) bacteria

6

What does Vancomycin bind to?

D-ala-D-ala

-Blocks cross-linking reaction

7

What is the phenotype of vancomycin resistance?

D-ala-D-ala → D-ala-D-lac

8

What is Vancomycin Intermediate S. aureus (VISA)?


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

9

What is cycloserine?

-cell wall synthesis inhibitor

-blocks D-ala ligase

*needs to enter cytoplasm

10

Which antibiotics inhibits the 30s segment of bacterial ribosomes?

-Aminoglycosides

-Tetracyclines

-Tigecycline

11

How do aminoglycosides work?

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

 

12

How is bacterial resistance to aminoglycocides mediated?

-Enzymatic inactivation of the drug

-A set of plasmid encoded enzymes can adenylate, phosphorylate or acetylate aminoglycosides

13

How do tetracyclines work?

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

14

How is bacterial resistance to tetracyclines work?

-active efflux of the drug out of the bacteria

-also by a plasmid-encoded tetracycline binding protein

15

How do macrolides work?

Bind 50S subunit and block translocation.

16

How do lincosamides work?

Bind 50S subunit and block translocation.

17

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

-Macrolides

-Lincosamides

-spectinomycin

-Chloramphenicol

-oxazolidinomes

18

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

-altered target site

19

How does chloramphenicol work?

-binds 50s subunit of ribosome

-inhibits peptidyl transferase to block peptide bond formation

20

What is the bacterial mechanism of resistance to chloramphenicol?

-enzymatic inactivation

21

How do oxazolidinones work?

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

22

What antibiotic classes inhibit bacterial folic acid metabolism?

-Sulfonamides

-Trimethoprim

23

How do sulfonamides work?

-inhibit bacterial purine/pryimidine synthesis

-blocks dihydropteroate synthetase

24

How does trimethoprim work?

-inhibits bacterial purine/pyrimidine synthesis

-inhibits DHFR

25

How is bacterial resistance of sulfonamides mediated?

By pass the blocked pathway

26

How is bacterial resistance of trimethoprim mediated?

Bypass the blocked pathway

27

What class of antibiotics are nucleic acid synthesis inhibitors?

-Quinolones

-Rifampicin

28

How do quinolones work?

-block DNA gyrase

& topoisomerase IV

29

How is bacterial resistance to quinolones mediated?

-mutations in gyrase and topo IV genes is the most common mechanism of resistance

-Efflux

-Qnr produced and binds/protects DNA gyrase

30

How does rifampicin work?

Blocks beta-subunit of the bacterial RNA polymerase enzyme

31

How is bacterial resistance to rifampicin mediated?

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

32

What antibiotics work via bacterial membrane disruption?

-Polymixins

-Daptomycin

33

How do polymixins work?

-act like a detergent and disrupt cytoplasmic membrane

*used topically due to toxicity

*resistance is rare

34

How does Daptomycin work?

-dysrupts cell membrane

-Depolarizes bacteria resulting in bacterial death from release of intracellular ions

35

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

aminoglycosides