Antimicrobials, Principles of Use and Antimicrobial Stewardship

Question 1

What is Antimicrobial Chemotherapy?

Answer 1

Use of drugs to combat infectious agents

Question 2

What are some examples of antiinfective agents?

Answer 2

Antivirals, antifungals, antibacterials, antiparasitic

Question 3

What does the concept of differential toxicity rely on?

Answer 3

the drug is more toxic to the infecting organism than to the host

Question 4

Most of the antibiotics currently are based on..?

Answer 4

naturally occurring compounds

- some may be synthetic or semi synthetic

Question 5

What is spectrum of activity and what are the two subtypes?

Answer 5

Refers to the killing ability of the antibiotic

• Narrow: kills only a few bacteria
• Broad: kills many organisms

Question 6

What is Minimum Inhibitory Concentration (MIC)?

Answer 6

minimum concentration of antibiotic required to inhibit the growth of the test organism.

Question 7

What is Minimum Bactericidal Concentration (MBC)?

Answer 7

The minimum concentration of antibiotic required to kill the test organism

Question 8

What does bacteriostatic mean? what is the relationship between MBC and MIC?

Answer 8

at therapeutic concentrations, the organism is inhibited

-MBC is often higher than the MIC

Question 9

What does bacteriocidal mean? What is the relationship between MBC and MIC?

Answer 9

at therapeutic concentrations, the organism is killed

-MIB and MBC are often the same

Question 10

What is prophylaxis?

Answer 10

When antimicrobial agents are administered to prevent infection

Question 11

What is “treatment”

Answer 11

When antimicrobial agents are administered to cure existing or suspected infection

Question 12

What is the therapeutic index?

Answer 12

The range of dosage amounts over which the drug is safe. Calculate by: Toxic dose (TD) / Effective dose (ED)

Question 13

What drug and what class of drugs have a narrow therapeutic index?

Answer 13

aminoglycosides, vancomycin

Question 14

What are 7 features that make an ideal antibiotic?

Answer 14

1. No / low toxicity to the host, well tolerated.
2. Low propensity for development of resistance.
3. Does not induce hyper-sensitivities in the host.
4. Rapid and extensive tissue distribution
5. Relatively long half-life.
6. Free of interactions with other drugs.
7. Convenient for administration / relatively inexpensive

Question 15

What is empiric therapy?

Answer 15

Treating patient with drug prior to getting lab results when they present with an infection needing immediate treatment

• based off of symptoms and most likely cause
• usually start with a broad acting agent and can narrow down with subsequent lab results

Question 16

What are 4 advantages to combination therapy?

Answer 16

1. Treating polymicrobial infections
2. Initial empiric therapy - broad coverage
3. Synergy
4. May prevent the emergence of resistance

Question 17

What are 4 disadvantages to combination therapy?

Answer 17

1. Antagonism
2. Cost
3. Increased risk of side effects / drug-drug interactions
4. Usually not necessary for maximal efficacy

Question 18

What is resistance?

Answer 18

the inability to kill or inhibit the organism with clinically achievable (or therapeutic) drug concentrations

Question 19

What are 2 ways in which resistance can be acquired?

Answer 19

1. Mutations in the genome

2. Acquisition of foreign DNA

Question 20

What are the 3 ways in which bacteria can obtain foreign DNA?

Answer 20

1. transformation: uptake of naked DNA
2. Transduction infected with phage
3. Conjugation: transfer of plasmid DNA

Question 21

What is the relationship between antibiotics and resistance?

Answer 21

select for resistance in a population of bacteria

- they are not mutagens

Question 22

There are 7 factors that might contribute to the development of resistance…

Answer 22

1. inadequate levels of antibiotics at the site of infection
2. duration of treatment too short / long
3. overwhelming numbers of organisms
4. overuse / misuse of antibiotics
5. poor quality counterfeits - animal husbandry
6. no prescription requirement (OTC)
7. frequent exposure – same class