(Lecture) Actions of Antimicrobials

Question 1

Chemical substances that are produced by microorganisms that has the capacity to inhibit or kill other microorganisms.

Answer 1

Antibiotics

Question 2

The lowest concentration of a drug that can inhibit bacterial growth.

Answer 2

Minimum-Inhibitory Concentration (MIC)

Question 3

The lowest concentration of a drug that can still kill bacteria.

Answer 3

Minimum-Bactericidal Concentration (MBC)

Question 4

Ratio of a toxic dose to the therapeutic dose; the higher the index, the more effective the chemotherapeutic agent.

Answer 4

Therapeutic Index

Question 5

Characteristics of Antimicrobial Agents

Answer 5

● The agent must be in active form.
● The agent must be able to achieve concentration at the site of infection that is higher than the pathogen’s MIC to be effective.
● Must have selective toxicity.

Question 6

_____ inhibit cell wall synthesis by binding to the end of the peptidoglycan, preventing transpeptidation.

Answer 6

Glycopeptides

Question 7

Glycopeptides inhibit cell wall synthesis by binding to the end of the peptidoglycan, preventing _____

Answer 7

Transpeptidation

Question 8

Glycopeptides inhibit cell wall synthesis by binding to the end of the _____, preventing transpeptidation

Answer 8

Peptidoglycan

Question 9

What type of Antimicrobial Agents is this based on the description?

● Selective antibiotics with high therapeutic index
● Interferes with the biosynthesis of peptidoglycan
● The beta-lactam antibiotics form covalent complexes with enzymes that generate mature peptidoglycan molecule (transpeptidase enzymes that mediate peptidoglycan cross-linking)
● The active component of the beta-lactam family of drugs is the beta-lactam structure.
● Glycopeptides inhibit cell wall synthesis by binding to the end of the peptidoglycan, preventing transpeptidation.

Answer 9

Cell Wall Inhibitors

Question 10

_____ prevents the formation of dihydropteroate through competitive inhibition of para-aminobenzoic acid with the enzyme dihydropteroate synthase

Answer 10

Sulfamethoxazole/SMZ

Question 11

Sulfamethoxazole/SMZ (a sulfonamide) prevents the formation of dihydropteroate through competitive inhibition of para-aminobenzoic acid with the enzyme _____

Answer 11

Dihydropteroate synthase

Question 12

Sulfamethoxazole/SMZ (a sulfonamide) prevents the formation of _____ through competitive inhibition of para-aminobenzoic acid with the enzyme dihydropteroate synthase

Answer 12

Dihydropteroate

Question 13

_____ blocks the formation of the tetrahydrofolate by inhibiting dihydrofolate reductase.

Answer 13

Trimethoprim

Question 14

Trimethoprim blocks the formation of the _____ by inhibiting dihydrofolate reductase.

Answer 14

Tetrahydrofolate

Question 15

Trimethoprim blocks the formation of the tetrahydrofolate by inhibiting _____

Answer 15

Dihydrofolate reductase

Question 16

What type of Antimicrobial Agents is this based on the description?

● The folic acid pathway provides essential precursor molecules needed for DNA biosynthesis
● Sulfamethoxazole/SMZ (a sulfonamide) prevents the formation of dihydropteroate through competitive inhibition of para-aminobenzoic acid with the enzyme dihydropteroate synthase
● Trimethoprim blocks the formation of the tetrahydrofolate by inhibiting dihydrofolate reductase.

Answer 16

Inhibitors of Folate Synthesis

Question 17

These are necessary for DNA replication

Answer 17

Topoisomerases I, II, III, and IV

Question 18

_____ affect DNA replication by targeting topoisomerases II (DNA gyrase) in Gram-negative bacteria and Topoisomerase IV in Gram-positive bacteria

Answer 18

Quinolones

Question 19

Quinolones affect DNA replication by targeting _____ in Gram-negative bacteria and _____ in Gram-positive bacteria

Answer 19

Topoisomerases II
Topoisomerases IV

Question 20

What type of Antimicrobial Agents is this based on the description?

● Topoisomerases I, II, III, and IV are necessary for DNA replication
● Quinolones affect DNA replication by targeting topoisomerases II (DNA gyrase) in Gram-negative bacteria and Topoisomerase IV in Gram-positive bacteria

Answer 20

Agents that Interfere with DNA Replication

Question 21

_____ of DNA into RNA is mediated by RNA polymerase

Answer 21

Transcription

Question 22

Transcription of DNA into RNA is mediated by _____

Answer 22

RNA polymerase

Question 23

_____ targets the RNA polymerase subunit, blocking RNA chain elongation.

Answer 23

Rifampin

Question 24

What type of Antimicrobial Agents is this based on the description?

● Transcription of DNA into RNA is mediated by RNA polymerase
● Rifampin targets the RNA polymerase subunit, blocking RNA chain elongation.

Answer 24

Agents that Interfere with DNA Transcription

Question 25

List down some of the antibiotics that target the 30S ribosomal subunit.

Answer 25

Aminoglycosides Spectinomycin Tetracyclines Glycylcyclines

Question 26

List down some of the antibiotics that target the 50S ribosomal subunit.

Answer 26

Macrolides Lincosamides Chloramphenicol Oxazolidinones Streptogramins

Question 27

Only _____ are bactericidal; the rest are bacteriostatic

Answer 27

Aminoglycosides

Question 28

Antibiotics that have side effects

Answer 28

Aminoglycosides, Chloramphenicol, and Tetracycline

Question 29

What type of Antimicrobial Agents is this based on the description? ● Some antibiotics target the 30S ribosomal subunit (aminoglycosides, spectinomycin, tetracyclines, glycylcyclines) ● Others target the 50S ribosomal subunit (macrolides, lincosamides, chloramphenicol, oxazolidinones, streptogramins) ● Only aminoglycosides are bactericidal; the rest are bacteriostatic ● Aminoglycosides, chloramphenicol, and tetracycline have side effects.

Answer 29

Agents that Inhibit Protein Synthesis

Question 30

_____ serve as outer membrane channels that permit the influx of nutrients and efflux of waste products.

Answer 30

Porins

Question 31

_____ are found in bacteria and function as transporter proteins for the extrusion of toxic substances and antibiotics from the interior of the cell to the external environment.

Answer 31

Efflux Pumps

Question 32

_____ are enzymes that hydrolyzes beta-lactams, preventing the antibiotic’s ability to bind transpeptidase enzymes

Answer 32

Beta-lactamases

Question 33

Beta-lactamases are enzymes that hydrolyzes beta-lactams, preventing the antibiotic’s ability to bind _____

Answer 33

Transpeptidase enzymes

Question 34

The inhibitors that bind beta-lactamases and reduces their detrimental effects on the beta-lactam antibiotics.

Answer 34

Clavulanic acid Sulbactam Tazobactam

Question 35

_____ compete with dihydropteroate synthase enzymes to block the formation of nucleotide precursors.

Answer 35

Sulfonamides