Lecture 13: Mechanisms of Action of Antibiotics

Question 1

To choose an appropriate antimicrobial therapy, what two factors relating to the infecting species must be known?

Answer 1

Identity

Suscpetibility

Question 2

What is empiric therapy?

Answer 2

If/when the identity of the infecting organism cannot be identified
Goes with most likely to cause infection, most likely susceptible

Question 3

What is AST? Why is it performed?

Answer 3

Antimicrobial sensitivity testing

Choose best drug

Question 4

What factors about the patient must be considered in choosing an appropriate antimicrobial therapy?

Answer 4

History (adverse reaction to drug), Age (and related symptoms/complications), pregnancy, renal and hepatic function (filtration), site of infection

Question 5

What are pharmacodynamics? What four stages does it include?

Answer 5

How the body manipulates drug
Absorption
Distribution
Metabolism
Excretion

Question 6

What are pharmacodynamics?

Answer 6

Biochemical and physiologic effects of drug

mechanism of action on bacteria

Question 7

What are bacteriostatic agents?

Answer 7

stop growth; don’t kill

Question 8

What are bacteriocidal agents?

Answer 8

irreversible damage; death

Question 9

What class of agent are Beta-lactam antibiotics?

Answer 9

Bacteriocidal

Question 10

What does the Minimal Inhibitory Concentration (MIC) of an antimicrobial agent mean?

Answer 10

Can be bacteriostatic at low concentrations, but bacteriocidal at higher concentrations

Question 11

What do broad spectrum antibiotics target?

Answer 11

both G+ and G-

Question 12

How are broad spectrum antibiotics used?

Answer 12

Empirically before causative bacteria is known

Question 13

What is an example of a narrow spectrum antibiotic?

Answer 13

Vancomycin - G- only

Question 14

What are the two most common antibiotic mechanisms of action?

Answer 14

1. Inhibit peptidoglycan synthesis (cell wall)

2. Interfere with protein synthesis

Question 15

What do antibiotic inhibitors of cell wall assembly interfere with?

Answer 15

Peptidoglycan synthesis

murein assembly

Question 16

What do Beta-lactam antibiotics inhibit?

Answer 16

Cell wall synthesis

Question 17

What are examples of beta-lactam antibiotics

Answer 17

penicillins
cephalosporins
monobactams
carbapenems

Question 18

What does vancomycin inhibit?

Answer 18

Cell wall synthesis

Question 19

What is the repeating unit of peptidoglycan?

Answer 19

NAG-NAM

Question 20

What enzyme catalyzes cell wall synthesis and is a target of some antibiotics? What kind of enzyme is it?

Answer 20

Penicillin Binding Proteins (PBP)

Transpeptidase enzyme

Question 21

How do beta-lactam antibiotics work?

Answer 21

mimics residue which would normally bind to active site of Penicillin Binding Proteins (transpeptidase enzyme)
irreversible

Question 22

What are extended-spectrum cephalosporins?

Answer 22

resistant to destruction by most beta-lactamases

Question 23

How are cephalosporins categorized by generation?

Answer 23

each generation has increased spectrum of activity

each generation has increased resistance to destruction to destruction to beta-lactamase enzymes

Question 24

What kind of bacteria produce beta-lactamase enzymes?

Answer 24

G-

Question 25

Which generations of cephalosporins are extended spectrum?

Answer 25

3 and 4

Question 26

What does ESBL stand for?

Answer 26

Estended Spectrum Beta-Lactamase

Question 27

Which two classes of antibiotics are resistant to destruction (effective against) EBSLs?

Answer 27

3rd and 4th generation cephalosporins

carbapenems

Question 28

What are the 5 main mechanisms of antibiotics? (Interfere with…)

Answer 28

cell wall synthesis
protein synthesis
cytoplasmic membrane function
nucleic acid synthesis
matabolic pathway

Question 29

What are the three ways antibiotics can inhibit protein synthesis?

Answer 29

interfere with formation of 30S initiation complex
interfere with formation of 70S ribosome
block elongation process of making peptide