Antibiotics III

Question 1

3 Steps of Peptidoglycan/Cell Wall Synthesis

Answer 1

1. Monomer biosynth/transport from cyt to periplasm
2. Monomer polymerization/transglycosidase
3. Polymer cross-linking/transpeptidation

Question 2

6 3rd Phase/Transpeptidation Inhibitors

Answer 2

Penicilliins
Methicillin
Ampicillin
Cephalosporins
Carbapenems
Monobactams

Question 3

1 2nd Phase/Transglycosidase Inhibitor

Answer 3

Vancomycin

Question 4

3 1st Phase Inhibitor (1st 2 biosynth 2nd transport)

Answer 4

Fosfomycin
Cycloserine
Bacitracin

Question 5

2 Inhibitors of Beta Lactamases

Answer 5

Clavulanic Acid

Sulbactam

Question 6

3 Aspects about Cell Wall Synth Inhibitors

Answer 6

Bactericidal
Require bacterial growth to be effective
Mechanism of death is autolysis (imbalance bw cell wall synth and degradation)

Question 7

2 Factors that Determine Spectrum

Answer 7

Hydrophilicity (ability to penetrate outer membrane and cell wall, more better)
Ability to Bind Specific Transpeptidases (bac have different ones)

Question 8

Mech of Beta Lactam Inactivation of Transpeptidases

Answer 8

Suicide substrate inhibition: covalent bond to enzyme

Question 9

Most Common Side Effect w/ Beta Lactams

Answer 9

Hypersensitivity from rxn to serum prots. If have to one beta lactam, don’t use others

Question 10

Most Common Resistance(s) to Beta Lactams

Answer 10

Plasmid-borne beta-lactamase (although intrinsic transpeptidase muts do occur)

Question 11

Penicillin G vs. V

Answer 11

G is acid labile, injected, while V is acid stable, oral

Question 12

Methicillin (2)

Answer 12

Beta-lactam refractor to beta-lactamase hydrolysis bc of steric hindrance of protective side chains
Only works for S. aureus

Question 13

Ampicillin

Answer 13

Broad spectrum penicillin bc has charged amino group that allows it to pass through membranes of G-

Question 14

Solution to Lack of Broad Spectrum Beta-Lactamase Refractory Penicillin

Answer 14

Combine broad spectrum penicillin w/ Beta-lactamase inhibitor

Question 15

MRSA

Answer 15

Methicillin resistant, still can’t hydrolyze but other intrinsic mechs on transposon easily transmitted w/ other resistance genes. Resistance often variable

Question 16

Cephalosporins (2)

Answer 16

R side chain makes them less of target for Beta-lactamases

Developed progressively to wider spectrum including G-s

Question 17

Carbepenems

Answer 17

Broad spectrum but not MRSA< C. dificile, or Legionella

Question 18

Monobactam (2)

Answer 18

Aztreonam active against G- but not G+. Nasty side effects

Question 19

Vancomycin (2m, ra, t, re, sf)

Answer 19

m - Inhibits peptidoglycan synth in 2 ways: inhibits NAM/NAG polymer synth & inhibits cross linking
ra - G+/MRSA
t - red man syndrome
re - VanA depsipentapeptide where crosslink chain is Lactate instead of Ala
sf - antibiotic of last resort

Question 20

Fosfomycin

Answer 20

Broad-spectrum MurA inhibitor effective on G- UTI

Question 21

Cycloserine

Answer 21

D-Ala analogue used against M. tuberculosis

Question 22

Bacitracin

Answer 22

Bactoprenol inhibitor used topically

Question 23

Daptomycin

Answer 23

Lipopeptide useful for G+/VRSA via cytoplasmic membrane depolarization