Test 2: antibiotics

Question 1

Penicillin and Cephalosporins

Answer 1

Cell wall synthesis inhibitor: Blocks transpeptidation; extracellular

Question 2

Bacitracin

Answer 2

Cell wall synthesis inhibitor: Complexes with inactive lipid, causes dolichol-P recycling; extracellular

Question 3

Vancomycin

Answer 3

Cell wall synthesis inhibitor: Blocks elongation of peptidoglycan backbone; extracellular

Question 4

Cycloserine

Answer 4

Cell wall synthesis inhibitor: D-ala analog interferes with transpeptidation; cytoplasm

Question 5

Phsophonomycin

Answer 5

Cell wall synthesis inhibitor: PEP analog inhibits conversion of NAM to NAG; cytoplasm

Question 6

Isoniazid (INH) and ethionamide

Answer 6

inhibits mycolic acid (TB drug that disrupts mycobacterial cell wall synthesis)
-similar structure to nicotinamide

Question 7

Ethambutol

Answer 7

TB drug disrupting cell wall: inhibits arabinogalactan synthesis (major component of mycobacterial cell wall)

Question 8

Aminoglycosides (streptomycin, gentomycin, neomycin)

Answer 8

Protein syntehsis inhibitor: blocks initiation of protein syntehsis; targets S12 of 30s subunit; targets polysomes, bactericidal

Question 9

Macrolides (erythromycin, azithromycin)

-linezolid (new drug)

Answer 9

Protein syntehsis inhibitor: inhibits initiation complex formation, targets 50s; both cidal and static

Question 10

Tetracycline

Answer 10

Protein syntehsis inhibitor: inhibits attachment of charged aminoacyl-tRNA, bacteristatic

Question 11

Chloramphenicol

Answer 11

Protein syntehsis inhibitor: Inhibits peptidyl transferase on 50s; bacteristatic

Question 12

Rifamycins (rifampin)

Answer 12

nucleic acid inhibitor: Inhibits DNA-dependent RNA polymerase, bactericidal that disrupts transcription, also anti TB therapy

Question 13

Quinolones (Cipro) and Levoquin

Answer 13

nucleic acid inhibitor: Inhibits DNA gyrase and regulation, disrupts replication; bactericidal

Question 14

Metronidazole/Flagyl

Answer 14

nucleic acid inhibitor: metabolites cause DNA strand breaks; induces fragmentation; bactericidal

Question 15

Polyenes (Nystatin, amphoteracin B)

Answer 15

Cell membrane inhibitor: antifungals that complex with ergosterol

Question 16

Imidazoles (miconazole and ketoconazole)

Answer 16

Cell membrane inhibitor: antifungal; blocks ergosterol synthesis

Question 17

Polymyxins

Answer 17

Cell membrane inhibitor: targets gram negative organisms; acts like a detergent and makes membranes leaky

Question 18

Sulfonamides (SMX)

Answer 18

antimetabolic: competes with PABA in folate biosynthetic pathway

Question 19

Trimethoprim (TMP)

Answer 19

Antimetabolic: Inhibits dihydrofolate reductase; bacteriostatic

Question 20

Penicillin+Streptomycin

Answer 20

penicillin enhances uptake of streptomycin

Question 21

Trimethoprom+sulfamethoxazole

Answer 21

blocks consecutive steps in folate metabolism

Question 22

Augmentin (amoxicillin+clavulonic acid)

Answer 22

clavulinic acid is beta lactamase inhibitor, used to help with MRSA

Question 23

Ideal antibiotic characteristics

Answer 23

• Bactericidal
• non-resistant
• non-allergenic
• stable under physiologic conditions
• SELECTIVE

Question 24

Therapeutic margin

Answer 24

Effective dose/toxic dose

Question 25

MOST important characteristic of an effective antibiotic?

Answer 25

Selective toxicity

Question 26

Penicillin binding proteins (PBPs)

Answer 26

-carboxypeptidase, amidases/glycosidases, and transpeptidases are bound by penicillin and inactivated–>autolysis

Question 27

Penicillin allergy

Answer 27

drug complexes with serum albumin and induces anaphylactic response

Question 28

How does a protoplast form?

Answer 28

In hypertonic environment bacteria does not lyse and will persist until drug is discontinued

Question 29

Streptomycin

Answer 29

good for CNS, can cause aplastic anemia

Question 30

Why do we use multiple drugs?

Answer 30

• prophy for immunocompromised
• chronic infection can lead to resistance
• broad spectrum used for unidentified organism
• mixed infections
• treat organisms that we know are hard to kill like TB