Antibiotic Mechanisms of Action

Question 1

Penicillin

Answer 1

Bind penicillin-binding proteins (transpeptidases) preventing cross-linking of peptidoglycan), activate autolytic enzymes

Question 2

Penicillinase-resistant penicillins

Answer 2

Same as penicillin, penicillinase resistant because of bulkier R group

Question 3

Aminopenicillins

Answer 3

Same as penicillin, penicillinase sensitive - so combine with clavulanic acid, amoxicillin has better oral bioavailability than ampicillin

Question 4

Antipseudomonals

Answer 4

Same as penicillin, Penicillinase sensitive - use with clavulanic acid

Question 5

Beta-lacatamase inhibitors

Answer 5

Added to penicillin antibiotics to protect the antibiotic from destruction by Beta-lactamase

Question 6

1st generation cephalosporins

Answer 6

Bactericidal, Beta-lactam drugs (bind to PBP’s) that inhibit cell wall synthesis but are less susceptible to penicillinases

Question 7

2nd generation cephalosporins

Answer 7

Bactericidal, Beta-lactam drugs (bind to PBP’s) that inhibit cell wall synthesis but are less susceptible to penicillinases

Question 8

3rd generation cephalosporins

Answer 8

Bactericidal, Beta-lactam drugs (bind to PBP’s) that inhibit cell wall synthesis but are less susceptible to penicillinases

Question 9

4th generation cephalosporins

Answer 9

Bactericidal, Beta-lactam drugs (bind to PBP’s) that inhibit cell wall synthesis but are less susceptible to penicillinases

Question 10

Aztreonam

Answer 10

Monobactam resistant to Beta-lactamases, prevents peptidoglycan cross-linking by binding to PBP3, synergistic with aminoglycosides

Question 11

Carbapenems

Answer 11

Broad spectrum Beta-lactamase resistant antibiotic, imipenim administered with cilastatin to inhibit renal inactivation by renal dehydropeptidase

Question 12

Vancomycin

Answer 12

Inhibits cell wall peptiodglycan formation by binding D-ala D-ala portion of cell wall precursors

Question 13

Aminoglycosides

Answer 13

Bactericidal; inhibits formation of intiation complex at 30s subunit of ribosomes, causing misreading of mRNA and blocking translocation; require O2 for uptake (ineffective against anaerobes!)

Question 14

Tetracyclines

Answer 14

Bacteriostatic, bind to 30S to prevent attachment of aminoacyl-tRNA, accumulates intracellularly

Question 15

Macrolides

Answer 15

Bacteriostatic, inhibit protein synthesis by blocking translocation, bind to 23S rRNA of 50S ribosomal unit

Question 16

Chloramphenicol

Answer 16

Bacteriostatic, blocks peptidyltransferase at 50S ribosomal subunit

Question 17

Clindamycin

Answer 17

Bacteriostatic, blocks translocation at 50S ribosomal subunit

Question 18

Sulfonamides

Answer 18

Bacteriostatic,, PABA antimetabolites inhibit dihydropteroate synthase (conversion of PABA+pteridine to DHF - eventually converted to THF)

Question 19

Trimethoprim

Answer 19

Bacteriostatic, inhibits bacterial dihydrofolate reductase (inhibiting conversion of dihydrofolic acid to tetrahydrofolic acid), used in combination with sulfonamides causing sequntial block of folate synthesis

Question 20

Fluoroquinolones

Answer 20

Bactericidal, inhibit DNA gyrase (topoisomerase II) and topoisomerase IV