Dr. Zhanel - Intro to Ab

Question 1

What is selective toxicity?

Answer 1

The ideal antimicrobial kills the harmful pathogen without damaging the human host

Question 2

_____ are synthesized in the lab

Answer 2

Antimicrobials

Question 3

______ are produced by bacteria and fungi

Answer 3

Antibiotics

Question 4

Describe “therapeutic index”

Answer 4

-It is a measure of safety

Upper limit - dose at which you get toxicity

Lower limit - dose at which you get therapeutic effect

Question 5

Do antimicrobial, antibiotic, antibacterial, and anti-infective have different meanings?

Answer 5

No, all mean the same thing

Question 6

Selective toxicity is often expressed as the ____ _____

Answer 6

therapeutic index

Question 7

Large therapeutic window = ____ drug

Answer 7

safe

Question 8

Define “broad spectrum”

Answer 8

Defines antibiotics that act against different kinds of pathogens (gram positives, gram negatives, typical and atypical bacteria, aerobes and anaerobes)

Question 9

What other categories can antibiotics be classified as ?

Answer 9

antibacterial, anti fungal, antiviral, antiparasitic

Question 10

When is bactericidal > bacteriostatic?

Answer 10

• Pt is immunocompromised
• More than 1 infection
• Infection in the brain (immune system does not help)
• Infection in heart tissue

Question 11

Bactericidal

Answer 11

Refers to the ability of an antibiotic to kill an organism (> 3 log10 reduction in original innoculum over 24 hours.

*3 log10’s = 99.9% of pathogen dead

This effect is often concentration dependent, species specific and media or biological fluid dependent.

Question 12

Bacteriostatic

Answer 12

Refers to reversibly inhibits growth (reduce < 3 log 10 over 24 hours). If the agent is removed, the organism regrows.

Complete eradication (all cells dead) of the pathogen frequently depends on the presence of the host’s immune system

Question 13

What is MIC (minimum inhibitory concentration) ?

Answer 13

• The activity of an antibiotic is often reported as the MIC (minimum inhibitory concentration) .
• The MIC is the lowest concentration of an antibiotic that prevents growth of the pathogen.

Question 14

What is MBC (minimum bactericidal concentration)?

Answer 14

-The MBC is the lowest concentration that kills (> 3 log10 reduction in original inoculum over 24 hours) the organism

Question 15

A ____ agent demonstrates a MBC/MIC of 2-4

Answer 15

bactericidal

Question 16

A _____ agent displays a very high MBC/MIC ratio (if it kills at all)

Answer 16

bacteriostatic

Question 17

Determining antibiotic susceptibility is performed by one of two ways: what are they?

Answer 17

1 - Dilution

• Test the bacteria’s susceptibility to the antibiotic by putting different strengths of antibiotic into tubes with the bacteria in it and see if the bacteria continues to grow.
• Doing this test, you determine the MIC

2 - Disk diffusion (Kirby bauer method)

• thin wafers containing antibiotic are placed onto cultured bacteria agar plates
• the zones of inhibition from the wafer are monitored to see if the bacteria are susceptible to the antibiotic or not.

Disk diffusion (E-test) 
*Instead of using a wafer, you use a strips and the antibiotic is leaked out of the strips to create zones of inhibition as well.

Question 18

Indifference

Answer 18

Addition of the killing effects

Question 19

Synergy

Answer 19

You get more activity using 2 drugs than when you use each of them separately

Question 20

Antagonism

Answer 20

One drug inhibits the other from working. Results in less activity when using 2 drugs than when you use them separately

Question 21

List some mechanisms of action of antibiotics

Answer 21

• Inhibit cell wall synthesis
• Inhibit protein synthesis
• Inhibition of enzymatic activity by antimetabolites
• Inhibition of nucleic acid synthesis