Antibiotics

Question 1

What are the 5 major categories of antibiotic mechanism?

Answer 1

Cell wall synthesis inhibitors, protein synthesis inhibitors, nucleic acid synthesis inhibitors, cell membrane disrupters, and antimycobacterials

Question 2

What classes of drugs are cell wall synthesis inhibitors?

Answer 2

Beta-lactams and Glycopeptides (Vancomycin)

Question 3

What are the subclasses of beta-lactam drugs?

Answer 3

Penicillins, cephalosporins, carbapenems, and monobactams

Question 4

What are the different categories of penicillins and what is the prototypial example of each?

Answer 4

Natural penicillins (Penicillin G); Aminopenicillins (ampicillin); penicillinase-resistant penicillins (nafcillin); and ureidopenicillins (piperacillin-tazobactam)

Question 5

What is the mechanism of action of beta-lactams?

Answer 5

They interfere with transpeptidases involved in cell wall synthesis

Question 6

What is the mechanism of resistance to beta-lactams?

Answer 6

Beta-lactamases; Altered affinity of transpeptidase or penicillin-binding proteins, efflux pumps, or decreased membrane permeability to the drugs

Question 7

How are the cephalosporins grouped? What is the prototype of each group?

Answer 7

1st Gen: Cefazolin; 2nd Gen: Cefoxitin; 3rd Gen: Ceftriaxone; Other Gen: Cefipime

Question 8

What class of drug is imipenem?

Answer 8

A carbapenem beta-lactam

Question 9

What class of drug is aztreonam?

Answer 9

Monobactam beta-lactam

Question 10

What is the mechanism of resistance against vancomycin?

Answer 10

R-plasmid codes for VanH (converts pyruvate to D-Lac) and VanA (binds D-Ala to D-Lac). When incorporated into the bacterial cell wall, vancomycin cannot bind

Question 11

What are the four major classes of antibiotic protein synthesis inhibitors? What are the prototypes of each class?

Answer 11

Aminoglycosides (Gentamycin), Macrolides (Azithromycin), Lincosamides (Clindamycin), and Tetracyclines (Minocycline)

Question 12

What is the mechanism of action of gentamycin?

Answer 12

Binds to 30S subunit of ribosome, halting translation

Question 13

What is the mechanism of resistance against gentamycin?

Answer 13

Enzymatic modification; decreased uptake, mutation in the ribosome

Question 14

What is the mechanism of action of azithromycin and clindamycin?

Answer 14

Prevent translocation of polypeptide chain

Question 15

What is the mechanism of resistance against azithromycin?

Answer 15

Efflux, ribosomal protection by methylation, esterase degradation of the drug, ribosomal mutations

Question 16

What is the mechanism of action for minocycline? The mechanism of resistance against minocycline?

Answer 16

Minocycline inhibits translocation by blocking the A site; Decreased uptake, active efflux, production of protection protein, and enzymatic inactivation all contribute to resistance

Question 17

What are the major categories of nucleic acid synthesis inhibiting antibiotics? What is the prototype of each?

Answer 17

Fluoroquinolones (Ciprofloxacin); Rifamycin (Rifampin); Nitroimidazoles (Metronidazole); and Sulfamides (trimethoprim-sulfamethoxazole)

Question 18

What is the mechanism of Ciprofloxacin’s action? Resistance against it?

Answer 18

Ciprofloxacin targets DNA gyrase (G-) and topoisomerase IV (G+)

Question 19

What is the mechanism of rifampin’s action? Resistance against it?

Answer 19

Rifampin inhibits DNA-dependent RNA polymerase; Altered target

Question 20

What is the mechanism of metronidazole’s action?

Answer 20

The prodrug gets an electron from ferredoxin to make a reactive nitro radical ion which targets and damages DNA

Question 21

What is the general mechanism of sulfonamides’ action? Resistance against it?

Answer 21

Sulfonamides are competitive inhibitors of dihydropteroate synthase (block folate synthesis); Altered affinity of enzymes for drug, decreased intake, active efflux, alternate pathway for folic acid synthesis

Question 22

What are the major antimycobacterials?

Answer 22

Isoniazid, Ethambutol, and Pyrazinamide