Antibiotics (Exam 1)

Question 1

Beta-lactams, glycopeptides, polypeptides, and others all act on what part of the bacteria?

Answer 1

disrupt the bacterial cell wall

Question 2

Fosfomycin prevents…

Answer 2

addition of NAG to NAM-UDP

Question 3

Cyclserine prevents…

Answer 3

addition of alanine subunits to NAM (to form the polypeptide chain) while IN THE CYTOPLASM

Question 4

Vancomycin prevents…

Answer 4

addition of the NAM-NAG repeat unit to the peptidoglycan chain IN THE PERIPLASM

Question 5

Penicillin prevents…

Answer 5

transpeptidation cross linking between peptide chains IN THE PERIPLASM

Question 6

Beta-lactams inhibit….

Answer 6

transpeptidation (mimics D-ala-D-ala structure which blocks the peptide chains from crosslinking)

Question 7

Cephalosporin has similar action to….

Answer 7

penicillin (beta lactams)

Question 8

Calvulanic acid, sulbactam, and tazobactam are all…

Answer 8

beta-lactamase inhibitors

Question 9

What is the action of bacitracins?

Answer 9

prevent recycling of the bactoprenol (lipid carriers) that transport NAM-NAG repeat units to the periplasm

Question 10

What do polymixins do?

Answer 10

bind phospholipids and disrupt outer and inner membranes of cells so better for gram negative bacteria. General mode of action harms human cells so more toxic

Question 11

Isoniazid, ethionamide, and ethambutol all act on…

hint: mycobacteria

Answer 11

mycolic acid (wax in cell wall of mycobacteria)

Question 12

Basic mechanism of oxazoladinones, tetracyclines, aminoglycosides, chloramphenicol, lincosamides, and macrolides antibiotics?

Answer 12

Inhibition of protein synthesis

Question 13

Mechanism of action of oxazolidinones?

Answer 13

-bind 23s rRNA of 50s subunit and prevents 70s initiation complex

Question 14

Mechanism of action of tetracyclines?

Answer 14

-binds 16s rRNA of 30s subunit and prevents binding of aa-tRNA to A site

Question 15

Mechanism of action of aminoglycosides?

Answer 15

-binds to 30s subunit and distorts A site, causing translation misreading

Question 16

Mechanism of action of chloramphenicol and lincosamides?

Answer 16

-bind to 50s subunit and inhibit peptidyltransferase activity

Question 17

Mechanism of action of macrolides?

Answer 17

• binds 23s rRNA in the 50s subunit and block translocation reaction
• also prevents formation of 50s subunit

Question 18

Basic mechanism of action of quinolones, rifampin/rifabutin, and metronidazole?

Answer 18

inhibition of nucleic acid synthesis

Question 19

Mechanism of action of quinolones? (aka ciprofloxacin and other floxacins)

Answer 19

• interferes with Type II topoisomerases (DNA gyrase or topoisomerase IV) and stabilize DNA double strand breaks
• cell can’t rejoin double strand breaks*

Question 20

Mechanism of action of rifampin/rifabutin?

Answer 20

-binds to bacterial RNA polymerase and prevents initiation of transcription

Question 21

Mechanism of action of metronidazole?

Answer 21

• produces DNA-damaging radicals under anaerobic conditions via enzymes functioning in anaerobes and microanaerobes (aka in the gut)
• prodrug with no inherent antimicrobial activity*

Question 22

Basic mechanism of action of sulfonamides, trimethoprim, dapsone, and p-aminosalicylic acid?

Answer 22

antimetabolites

Question 23

Resistance mechanism to penicillins and cephalosporins?

Answer 23

hydrolysis of beta-lactam ring by beta-lactamase

Question 24

Resistance mechanism to methicillin?

Answer 24

change in penicillin-binding protein

Question 25

Resistance mechanism to tetracyclines?

Answer 25

efflux pump pushes drug out of the cell

Question 26

Resistance mechanism to oxazolidinones?

Answer 26

mutations in the 23s rRNA

Question 27

Resistance mechanism to quinolones?

Answer 27

mutations in genes encoding DNA gyrase and topoisomerase IV

Question 28

Resistance mechanism to vancomycin?

Answer 28

change in binding site in peptidoglycan target. (D-ala-D-ala change to D-ala-D-lactate)