Mechanisms of Antibiotic Action

Question 1

B-lactams: cephalosporins, penicillins, carbapenems, monobactams

Answer 1

Interfere with cell wall cross-linking through interaction with penicillin-binding proteins (transpeptidases); autolysis

Question 2

Glycopeptides: Vancomycin

Answer 2

Interfere with incorporation of new subunits into growing murein chains

Question 3

Imidazoles: fluconazole, itraconazole, voriconazole, posaconazole

Answer 3

Blocks synthesis of ergosterol required for fungal cell wall integrity

Question 4

Echinocandins: caspofungin, micafungin

Answer 4

Blocks B-glucan synthesis, a major constituent of fungal cell walls

Question 5

Lipopeptide antibiotics: daptomycin

Answer 5

Forms channels in cell membranes of gram-positive bacteria resulting in K+ leakage and metabolic death

Question 6

Polyene: amphotericin B

Answer 6

Bind to sterols in eukaryotic cell membranes, leading to membrane leakiness and, at high levels lysis

Question 7

Sulfonamides: sulfamethoxazole

Answer 7

Competitive inhibitor of dihydropteroate synthesis; blocks synthesis of tetrahydrofolate and sulfadiazine cell-linked metabolic pathways

Question 8

Trimethoprim

Answer 8

Inhibition of bacterial dihydrofolate reductatse

Question 9

Aminoglycosides: gentamycin, tobramycin, streptomycin, amikacin, neomycin

Answer 9

Bind to 30S subunit of bacterial ribosomes; cause translational misreading and inhibit elongation of protein chains; kill by blocking initiation of protein synthesis

Question 10

Macrolides: erythromycin, azithromycin, clarithromycin, clincamycin

Answer 10

Bind to ribosome 50S subunit; inhibit protein synthesis at chain elongation step

Question 11

Ketolides: telithromycin

Answer 11

Bind to ribosome 50S subunit; inhibit protein synthesis at chain elongation step

Question 12

Streptogramins: dalfopristin, quinopristin

Answer 12

Bind to ribosome 50S subunit; inhibit protein synthesis at chain elongation step

Question 13

Chloramphenicol

Answer 13

Bind to ribosome 50S subunit; inhibit protein synthesis at chain elongation step

Question 14

Rifampin

Answer 14

Binds to bacterial RNA polymerase and blocks transcription at initiation step

Question 15

Metronidazole, nitrofurans

Answer 15

Partially reduced nitro groups give addition products on DNA that lead to cidal strand breakage

Question 16

Flouroquinolones: ciprofloxacin, levofloxacin, gatifloxacin, moxifloxacin, gemifloxacin

Answer 16

Interfere with DNA replication by inhibiting the action of DNA gyrase or topoisomerase

Question 17

Nalidixic acid

Answer 17

Interfere with DNA replication by inhibiting the action of DNA gyrase or topoisomerase