Antibiotics: Classes and Mechanisms

Question 1

What is the general spectrum of penicillin G and V? How are they administered?

Answer 1

Narrow spectrum (Strep, oral anaerobes, syphilis); G is i.v. and V is oral

Question 2

What is the general spectrum of oxacillin and dicloxacillin? How are they administered?

Answer 2

Very narrow spectrum (Strep, MSSA); oxacillin is i.v. and dicloxacillin is oral

Question 3

What is the general spectrum of ampicillin and amoxicillin? How are they administered?

Answer 3

Broad spectrum (Strep, MSSA, H. flu, anaerobes); ampicillin is i.v. and amoxicillin is oral

Question 4

What is the general spectrum of piperacillin? How is it administered?

Answer 4

Extended spectrum (Strep, MSSA, anaerobes, Gram(-) rods); given i.v.

Question 5

Name the 2 first generation cephalosporins. How are they administered?

Answer 5

Cefazolin (i.v.) and cephalexin (oral)

Question 6

Name the second generation cephalosporin. What protein does it bind to inhibit cell wall synthesis?

Answer 6

Cefuroxime; binds PBP2x

Question 7

Name the 3 third generation cephalosporins. Which one is given orally?

Answer 7

Ceftazadime, ceftriaxone, and cefpodoxime; cefpodoxime is oral

Question 8

Name the fourth generation cephalosporin.

Answer 8

Cefepime

Question 9

What are the 2 PBP-binding β-lactams that are neither penicillins nor cephalosporins? Which one only works on Gram(-) aerobic rods like Pseudomonas?

Answer 9

Imipenem (a carbapenem) and aztreonam (a monobactam); aztreonam targets Gram(-) aerobes

Question 10

What is the glycopeptide that works by inhibiting transpeptidation? What amino acid does it bind to?

Answer 10

Vancomycin; binds alanine (in the D-ala-D-ala group of the cell wall)

Question 11

Cilastatin is given with what antibacterial drug to prevent overly rapid degradation and formation of toxic metabolites?

Answer 11

Imipenem

Question 12

Name the 2 cell membrane toxin antibacterials. In what kind of bacteria does each one form a channel/pore to allow leakage of intracellular ions?

Answer 12

Daptomycin - kills Gram(+) cocci like VRE and VRSA, and colistin - kills Gram(-) like Pseudomonas

Question 13

Name the 2 aminoglycosides. What subunit and function of the bacterial ribosome do they affect?

Answer 13

Gentamicin and tobramycin; bind the 30S subunit to cause codon-anticodon misreading (and to prevent initiation of transcription)

Question 14

Name the tetracycline antibiotic. What subunit and function of the bacterial ribosome does it affect?

Answer 14

Doxycycline; binds the 30S subunit to inhibit tRNA attachment to the ribosome

Question 15

Which 2 antibiotics bind the 50S subunit to inhibit tRNA translocation from the “A” to “P” site? Which one is a macrolide?

Answer 15

Azithromycin (macrolide) and clindamycin

Question 16

Which antibiotic has replaced chloramphenicol, which had a high rate of aplastic anemia? What subunit and function of the bacterial ribosome does it affect?

Answer 16

Linezolid; binds the 50S subunit to inhibit peptidyl transferase

Question 17

Which antibiotic is most strongly associated with C. difficile infection? Specifically, how does it inhibit tRNA translocation?

Answer 17

Clindamycin; inhibits peptide bond formation by binding the 50S subunit at the “A” site

Question 18

Name the first and second generation fluoroquinolones. What enzymes do they inhibit?

Answer 18

Ciprofloxacin (1st); levofloxacin (2nd); inhibit DNA gyrase (at lower doses) and topoisomerase IV (only levo, at higher doses)

Question 19

What kind of environment activates metronidazole, and how does it inhibit bacterial growth?

Answer 19

Is reduced to a free radical in an anaerobic environment, which directly damages DNA

Question 20

Name the two drugs that make Bactrim. What enzymes do they inhibit?

Answer 20

TMP-SMX, trimethoprim-sulfamethoxazole; inhibit DHFR (DHF–> THF) and dihydropterate synthase (pteridine + PABA –> dihydropteric acid)

Question 21

What 4 drugs are used to treat active TB?

Answer 21

Isoniazid, rifampin, pyrazinamide, ethambutol

Question 22

Which 2 TB drugs inhibit mycolic acid synthesis? Which is a prodrug and B6 cogener?

Answer 22

Isoniazid and pyrazinamide; isoniazid is the prodrug/B6 cogener

Question 23

Which TB drug is a nucleic acid synthesis inhibitor that targets DNA-dependent RNA polymerase?

Answer 23

Rifampin

Question 24

Which TB drug inhibits arabinogalactan synthesis for the mycobacterial cell wall by blocking arabinosyl transferases?

Answer 24

Ethambutol