Antibiotic Action

Question 1

beta-lactams (penicillin, cepalosporin)

Answer 1

inhibit the final transpeptidation reaction in cross-linking of peptidoglycan

Question 2

Vancomycin

Answer 2

inhibit the polymerization of NAM and NAG onto peptidoglycan

Question 3

Cycloserine

Answer 3

inhibits the isomerization from L to D aa

Question 4

Cell-wall active antimicrobials?

Answer 4

beta lactams (penicillin, cepalosporin…), vancomycin, cycloserine

Question 5

Outer and cytoplasmic membrane-active antimicrobials?

Answer 5

Polymyxin

Question 6

Polymyxin

Answer 6

cationic surfactants disrupting bacterial outer and cytoplasmic membrane

Question 7

Which one inhibits protein synthesis at the ribosomal level?

Answer 7

Aminoglycoside, tetracylines, chloramphenicol, macrolides

Question 8

How aminoglycosides and tetracylcines, etc… prevent from harming human protein synthesis?

Answer 8

Selective toxicity is due to difference between bacterial and mammalian ribosomes.

Question 9

Aminoglycoside representative drugs?

Answer 9

streptomycin
kanamycin
gentamicin
neomycin
tobramycin
amikacin

Question 10

Aminoglycoside action?

Answer 10

bind to specific target proteins in the 30S ribosomal subunit and inhibit protein synthesis

Question 11

Tetracycline

Answer 11

reversibly bind 30S ribosomal subunit and inhibit binding of aminoacyl tRNA

Question 12

Chloramphenicol

Answer 12

bind reversibly 50S ribosomal subunit

inhibit peptidyl transferase and peptide bond formation

Question 13

Macrolides and lincomycins representative drug?

Answer 13

Macrolides: erythromycin
Lincomycins: lincomycin and clindamycin

Question 14

Macrolides and lincomycins action?

Answer 14

bind 23S ribosomal RNA of the 50S subunit

inhibit peptidyl transferase

Question 15

Which drugs inhibit nucleic acid synthesis?

Answer 15

Quinolones

Rifampicin

Question 16

Quinolones

Answer 16

inhibit DNA gyrase & topoisomerase

interfere DNA replication

Question 17

Rifampicin

Answer 17

inhibits RNA polymerase

interfere with transcription initiation

Question 18

Which drugs are metabolic inhibitory antimicrobials?

Answer 18

Sulfonamide
Trimethroprim
Isoniazid
Metroniadazole

Question 19

Sulfonamide

Answer 19

(structural analog of p-aminobenzoic acid) competitively inhibit formation of folic acid, preventing nucleic acid synthesis

Question 20

How sulfonamide selective for bacteria?

Answer 20

only bacteria, NOT human, possess enzymes for making folic acid

Question 21

Trimethoprim

Answer 21

inhibiting enzyme dihydrofolate reductase

interfere with folate metabolism

Question 22

How trimethoprim selective for bacteria?

Answer 22

Both bacterial and human cells have dihydrofolate reductase. However, bacterial enzyme is 50000-fold greater sensitivity to the drug –> selective toxicity.

Question 23

Isoniazid

Answer 23

inhibit lipid synthesis

Question 24

Metronidazole

Answer 24

interfere with anaerobic metabolism

Question 25

Aerobe

Answer 25

+ Aerobic
- Anaerobic
Requires oxygen; can NOT ferment

Question 26

Anaerobe

Answer 26

• Aerobic
  + Anaerobic
  Killed by oxygen; fermentative metabolism

Question 27

Indifferent (aerotolerant anaerobe)

Answer 27

+ Aerobic
+ Anaerobic
Ferment w/ or w/o oxygen

Question 28

Faculative

Answer 28

+ aerobic
+ anaerobic
respire with oxygen
ferment w/o oxygen

Question 29

Microaerophilic

Answer 29

+/+
Grow best at low oxygen
Can grow w/o