Microbio antibiotics general

Question 1

Trimethoprim resistance

Answer 1

Plasmid-coded, trimethoprim-resistant dihydrofolate reductase.

Question 2

Penicilllin resistance

Answer 2

Hydrolysis of ß-lactam ring by ß-lactamase enzyme; decreased Cephalosporins permeability of bacteria to the antibiotic; altered penicillin binding proteins

Question 3

Methicillin resistance

Answer 3

Altered penicillin binding proteins (not in ß-lactamase). (a ß-lactamase-resistant penicillin).

Question 4

Aminoglycosides resistance

Answer 4

Enzymatic modification of drug by plasmid-coded enzyme; decreased permeability of bacteria to the antibiotic; mutation alters site to which antibiotic normally binds (e.g. S12 ribosomal protein for streptomycin).

Question 5

Tetracyclines resistance

Answer 5

Interference with transport of drug into cell.

Question 6

Chloramphenicol resistance

Answer 6

Detoxification of drug by acetylation of hydroxyl.

Question 7

Erythromycin resistance

Answer 7

Enzymatic methylation of 23S ribosomal RNA.

Question 8

Ciprofloxacin, Rifampin resistance

Answer 8

Altered target enzymes (gyrase, RNAP)

Question 9

Vancomycin resistance

Answer 9

Alteration of cell wall precursor target.

Question 10

antimetabolites (sulfonamides, trimethoprim) mechanism of action

Answer 10

Inhibit synthesis of dihydrofolate, ultimately nucleic acid synthesis.

Question 11

Antimetabolite (flucytosine) mechanism of action

Answer 11

inhibits thmidylate synthetase and ultimately DNA synthesis

Question 12

Isoniazid mechanism of action

Answer 12

Inhibits synthesis of mycolic acid (specific for Mycobacteria).

Question 13

b-Lactams (penicillins, cephalosporins) mechanism of action

Answer 13

Interfere with cell wall biosynthesis. Inhibition of transpeptidation weakens cell wall. Autolytic enzymes of bacteria then promote lysis.

Question 14

Glycopeptides (cycloserine, bacitracin, vancomycin, teichoplanin, caspofungin) mechanism of action

Answer 14

Interfere with cell wall biosynthesis.

Question 15

Polymyxins and polyenes (nystatin, amphotericin B daptomycin) mechanism of action

Answer 15

Disrupt membrane integrity.

Question 16

Aminoglycosides (streptomycin) mechanism of action

Answer 16

Inhibit protein synthesis by binding to a specific protein of 30S ribosomal subunit.

Question 17

Aminoglycosides (gentamicin, kanamycin neomycin, amikacin tobramycin) mechanism of action

Answer 17

Bind to 30S ribosomal subunit at multiple sites. Inhibit protein synthesis.

Question 18

tetracyclines mechanism of action

Answer 18

Block protein synthesis by inhibiting binding of amino-acyl t-RNA to 30S subunit.

Question 19

Macrolides (Erythromycin, azithromycin), clindamycin, chloramphenicol mechanism of action

Answer 19

bind to 50S ribosomal subunit. Inhibit protein synthesis at chain
elongation step.

Question 20

Oxazolidinones (linezolid) mechanism of action

Answer 20

Bind rRNA on both ribosomal subunits (new)

Question 21

Streptogramins (dalfopristin, quinupristin) mechanism of action

Answer 21

Bind to 50S ribosomal subunit (new)

Question 22

Mupirocin mechanism of action

Answer 22

Binds isoleucyl tRNA synthetase, preventing charging of Ile-tRNA and thus affecting protein synthesis.

Question 23

Fluoroquinolones ciprofloxacin mechanism of action

Answer 23

Inhibit bacterial DNA gyrase.

Question 24

Nitroimidazoles mechanism of action

Answer 24

fragments DNA

Question 25

Rifampin mechanism of action

Answer 25

binds to bacterial RNA polymerase and blocks transcription

Question 26

Azoles (fluconazole, ketoconazole) mechanism of action

Answer 26

Inhibit ergosterol synthesis.

Question 27

Ethambutol mechanism of action

Answer 27

unknown, anti-TB

Question 28

Pyrazinamide mechanism of action

Answer 28

unknown, anti-TB