Antimicrobial Agents & Resistance

Question 1

Antibacterial agents that inhibit protein synthesis (7)

Answer 1

1. Aminoglycosides
2. Tetracyclines
3. Macrolides
4. Oxazolidenones
5. Streptogramins
6. Lincosamides
7. Chloramphenicol

ALMOST C

Question 2

Bacterial Ribosome Units

Answer 2

50S & 30S (70S)

Question 3

30S protein synthesis inhibitors

Answer 3

Aminoglycosides
Tetracyclines

A(lmos)T (c)

Question 4

50S protein synthesis inhibitors

Answer 4

Chloramphenicol
Macrolides
Lincosamides
Streptogramins
Oxazolidinones

(a)LMOS(t) C

Question 5

Aminoglycosides: function

Answer 5

Bactericidal, Gram - rods
Bind 30S
Disrupt LPS in outer membrane

Question 6

Aminoglycosides: examples

Answer 6

Streptomycin

Gentamicin

Question 7

____ are intrinsically resistant to aminoglycosides

Answer 7

Anaerobes

Question 8

Aminoglycosides: resistance

Answer 8

1. Enzymatically inactivate drug (with modification)
2. Alter drug target (methylation of rRNA, mutation of ribosomal protein)
3. Alter drug exposure (decrease uptake, increase efflux)

Question 9

Aminoglycosides: combination therapy

Answer 9

+ beta-lactams; aminoglycosides give beta-lactams greater access to PBPs

Question 10

Tetracyclines: function

Answer 10

Bacteriostatic, G-/+, mycoplasma, and intracellular bacteria
Bind 30S subunit
Selectivity for bacteria vs host cell

Question 11

Tetracyclines: examples

Answer 11

Tetracycline

Doxycycline

Question 12

Tetracycline: contraindications/limits

Answer 12

Contraindicated in pregnancy & young children (inhibition of bone growth)
Ca2+ and Mg2+ inhibit absorption in GI tract (avoid antacids and milk)

Question 13

Should avoid combinations of Tetracycline and ____

Answer 13

Bactericidal agents; beta-lactams (penicillin)

Question 14

Tetracyclines: resistance

Answer 14

1. Alter drug exposure (efflux pumps)

2. Alter drug target (ribosome protection proteins)

Question 15

Chloramphenicol: function

Answer 15

Bacteriostatic, binds 50S subunit

Question 16

Chloramphenicol is bactericidal against ____

Answer 16

Important encapsulated organisms

Question 17

Chloramphenicol: resistance

Answer 17

Enzymatically inactivate drug (modification by acetyl transferases)

Question 18

Macrolides: function

Answer 18

Bacteriostatic, mostly G+

Bind 50S subunit

Question 19

Macrolides: examples

Answer 19

Erythromycin

Azithromycin

Question 20

Macrolides: resistance

Answer 20

erm genes –> modify 50S subunit with methylation to prevent macrolide binding

Question 21

Lincosamides: function

Answer 21

Bacteriostatic, G+/- anerobes

Bind 50S subunit

Question 22

Lincosamides: example

Answer 22

Clindamycin

Question 23

Lincosamides are associated with what disease?

Answer 23

C. difficile-associated pseudomembranous colitis

Question 24

Streptogramins A & B: function

Answer 24

Individually ‘static, together ‘cidal
A: stops peptide-bond formation
B: stops chain elongation

Question 25

MLS(B) resistance

Answer 25

Resistance to Macrolides, Lincosamides & Streptogramins B
Cross-resistance, altered drug target (erm gene –> ribosomal methylation)

Question 26

erm expression can be ___ or ____ in _____

Answer 26

constitutive, inducible, staphylococci

Question 27

D-test results

Answer 27

D shape around lincosamide (CL) next to constitutively resistant ERY = inducibly resistant

Question 28

Oxazolidinones: function

Answer 28

Bacteriostatic, G+

Bind to 23S RNA in 50S subunit

Question 29

Oxazolidinones: example

Answer 29

Linezolid

Question 30

Oxazolidinones: resistance

Answer 30

Alter drug target: mutations in 23S rRNA gene

Question 31

Antibiotics that inhibit peptidoglycan synthesis (5)

Answer 31

1. Phosphomycin
2. Cycloserine
3. Bacitracin
4. Glycopeptides
5. Beta-lactams

Question 32

Antibiotics that inhibit peptidoglycan synthesis

Answer 32

1. Isoniazid (inh mycolic acid synthesis)

2. Ethambutol (inh arabinotransferases)

Question 33

Lipopeptides: function/example

Answer 33

disrupt cell membrane of G+ bacteria; bind phosphatidyl glycerol
1. Daptomycin

Question 34

Folate synthesis inhibitors

Answer 34

1. Trimethoprim

2. Sulfonamides

Question 35

DNA synthesis inhibitors

Answer 35

1. Fluoroquinolones

Question 36

RNA synthesis inhibitors

Answer 36

1. Rifamycins

Question 37

Agents that damage DNA

Answer 37

1. Nitroimidazoles

Question 38

Two types of Vancomycin resistance in enterococci/staphylococci

Answer 38

1. VanA locus: constitutive resistance

2. VanB locus: inducible resistance