Antibiotics

Question 1

Antimicrobial therapy relies on what principle tenet?

Answer 1

Selective toxicity

Question 2

What contributes to antibiotic resistance?

Answer 2

Genetic mutation and/or acquisition of genetic elements from other bacteria carrying resistance genes

Question 3

What are the mechanisms of antibiotic resistance?

Answer 3

1. Breakdown2. Chemical modification 3. Alteration4. Altered permeability, decreased influx or increased efflux5. Lack of target

Question 4

What is bacteriostatic activity?

Answer 4

Level of antimicrobial activity that INHIBITS growth

Question 5

What is the MIC?

Answer 5

1. Minimum inhibitory concentration2. Lowest concentration of antibiotic that inhibits growth

Question 6

What is bactericidal activity?

Answer 6

Level of antibiotic that KILLS

Question 7

What is the MBC?

Answer 7

1. Minimum bactericidal concentration2. Lowest concentration of antibiotic that kills 99.9%

Question 8

What tests can give you the MIC?

Answer 8

1. Disk diffusion assay (circles)2. E-test (leaves)3. Broth culture

Question 9

What are characteristics of cell wall active antibiotics?

Answer 9

1. Disrupts peptidoglycan synthesis2. Effective against actively dividing bacteria

Question 10

What are characteristics of membrane active antibiotics?

Answer 10

1. Disrupts or interferes with membrane integrity / synthesis2. Effective against resting and actively dividing bacteria

Question 11

How do B-lactams inhibit cell wall synthesis?

Answer 11

1. Bind to PBPs or other transpeptidases (cover active serine site)2. Prevents addition of another peptidoglycan sheet to growing wall

Question 12

How is B-lactam resistance conferred?

Answer 12

1. Mutation so that B-lactams can no longer bind to active serine site of PBPs2. Pumped out of periplasmic space3. Altered permeability involving porins

Question 13

How does vancomycin inhibit bacterial growth?

Answer 13

1. Recognizes and binds to two D-ala residues on peptide chains2. Prevents peptide chains from interacting properly with transpeptidase3. Cross links cannot be formed

Question 14

How are bacteria resistant to vancomycin?

Answer 14

D-ala residue replaced by a D-lactate

Question 15

How does bacitracin inhibit bacterial growth?

Answer 15

1. Inhibits cycling of peptidoglycan to outer leaflet2. Double phosphorylated bactoprenol builds up and cannot be used by cell

Question 16

What are characteristics of tetracyclines?

Answer 16

1. Bacteriostatic2. Bind 30S subunit3. Broad spectruum

Question 17

What are characteristics of aminoglycosides?

Answer 17

1. Generally bactericidal2. Bind 30S subunit3. Oxygen dependent4. Effective only against aerobic organisms

Question 18

What are characteristics of macrolides?

Answer 18

1. Bind 50S ribosome2. Used as an alternate for individuals with penicillin allergy

Question 19

What are characteristics of quinolones?

Answer 19

1. Bactericidal2. Inhibits DNA replication, recombination, and repair

Question 20

What are characteristics of rifampin and rifabutin?

Answer 20

Bind to DNA dependent RNA polymerase and inhibits initiation of RNA synthesis

Question 21

What are characteristics of metronidazole?

Answer 21

Reduced by bacteria = toxic compounds that damage DNA

Question 22

What are characteristics of antimetabolites?

Answer 22

1. Target folate metabolism2. Sulfonamides, trimethoprim