25. Antibiotics

Question 1

PG monomer is made of repeating units of _____ and _____ + ________

Answer 1

NAM and NAG + pentapeptide

Question 2

Between G+/G-, what part of PG monomer is conserved?

Answer 2

D-Ala-D-Ala

Question 3

What 2 types of activities do PBPs have?

Answer 3

Transpeptidase, transglycosylase

Question 4

Transglycosylase activity = what linkage?

Answer 4

NAM-NAG

Question 5

Transpeptidase activity = what linkage?

Answer 5

G+ = pentapeptides via pentaglycine
G- = direct linkage

Question 6

Target of transpeptidases/PBPs?

Answer 6

D-Ala-D-Ala

Question 7

____% bacteria are resistant to beta-lactams

Answer 7

> 80%

Question 8

2 examples of beta-lactamases inhibitors?

Answer 8

Clavulanic acid, sulbactam

Question 9

Beta-lactamases hydrolyze ______ in the beta-lactam ring

Answer 9

C-N bond

Question 10

2 ways antibiotic resistance arise

Answer 10

Mutations, mobile genetic elements

Question 11

Antibiotics are classified based on what 4 things?

Answer 11

• Bacterial spectrum
• Route of admin
• Type of activity (bacterio-cidal/static)
• Chemical structure (beta-lactam..)

Question 12

4 strategies used to resist antibiotics?

Answer 12

• Restric access/efflux pumps
• Modify antibiotic
• Modify antibiotic target
• Immunity and bypass

Question 13

Glycopeptides are used for gram-____ bacteria because..?

Answer 13

Gram-positive

Can’t penetrate G- OM

Question 14

Which 2 antibiotics affect folic acid synthesis (THF pathway)?

Answer 14

Trimethoprim, sulfonamide

Question 15

2 things bacteria can produce to be resistant to beta-lactams?

Answer 15

• beta-lactamases (modify antibiotic)

- altered PBPs (modify antibiotic target)

Question 16

beta-lactams mimic D-Ala-D-Ala and inhibits activity of what?

Answer 16

Transpeptidase activity of PBPs

Question 17

What class of antibiotics are carbapenems?

Answer 17

beta-lactams

Question 18

2 antibiotics that bind to 30S subunit?

Answer 18

Aminoglycosides, tetracycline

Question 19

Mechanism of aminoglycosides?

Answer 19

Incorrect incorporation of aa (distorts 30S = wrong tRNA binds)

Inhibits intiation and elongation of protein

Question 20

Mechanism of tetracycline?

Answer 20

Inhibit tRNA binding at “A” site by distorting it = block peptide synthesis

Question 21

Mechanism of chloramphenicol? Specifically, what does it prevent?

Answer 21

Binds ribosomal peptidyltransferase on 50S (no peptidyl transfer step)

Prevents peptide BOND formation

Question 22

Which 3 antibiotics inhibit the translocation step of protein synthesis? How?

Answer 22

Macroslides
Lincosamides
Streptogramins

Bind to 50S to prevent translocation

Question 23

Sulfonamides are competitive inhibitors of what?

Answer 23

Pteridine synthase in bacteria

Question 24

Trimethoprim is structurally similar to _____ and acts as a competitive inhibitor of what microbial (but not human_ enzyme?

Answer 24

DHF

DHF reductase