Dr. Zhanel - Intro to Ab Flashcards
What is selective toxicity?
The ideal antimicrobial kills the harmful pathogen without damaging the human host
_____ are synthesized in the lab
Antimicrobials
______ are produced by bacteria and fungi
Antibiotics
Describe “therapeutic index”
-It is a measure of safety
Upper limit - dose at which you get toxicity
Lower limit - dose at which you get therapeutic effect
Do antimicrobial, antibiotic, antibacterial, and anti-infective have different meanings?
No, all mean the same thing
Selective toxicity is often expressed as the ____ _____
therapeutic index
Large therapeutic window = ____ drug
safe
Define “broad spectrum”
Defines antibiotics that act against different kinds of pathogens (gram positives, gram negatives, typical and atypical bacteria, aerobes and anaerobes)
What other categories can antibiotics be classified as ?
antibacterial, anti fungal, antiviral, antiparasitic
When is bactericidal > bacteriostatic?
- Pt is immunocompromised
- More than 1 infection
- Infection in the brain (immune system does not help)
- Infection in heart tissue
Bactericidal
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.
Bacteriostatic
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
What is MIC (minimum inhibitory concentration) ?
- 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.
What is MBC (minimum bactericidal concentration)?
-The MBC is the lowest concentration that kills (> 3 log10 reduction in original inoculum over 24 hours) the organism
A ____ agent demonstrates a MBC/MIC of 2-4
bactericidal
A _____ agent displays a very high MBC/MIC ratio (if it kills at all)
bacteriostatic
Determining antibiotic susceptibility is performed by one of two ways: what are they?
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.
Indifference
Addition of the killing effects
Synergy
You get more activity using 2 drugs than when you use each of them separately
Antagonism
One drug inhibits the other from working. Results in less activity when using 2 drugs than when you use them separately
List some mechanisms of action of antibiotics
- Inhibit cell wall synthesis
- Inhibit protein synthesis
- Inhibition of enzymatic activity by antimetabolites
- Inhibition of nucleic acid synthesis
