7 Antibiotic Reactions, Use, and Resistance Flashcards
Name three adverse rxns associated w/ antibiotic use.
- Toxicity/intolerance
- Allergic rxns
- Disruption of “normal flora”
Of the three adverse rxns due to antibiotic use, THIS one is very rare.
Allergic rxns (anaphylaxis)
Three types of antibiotic therapy:
- Empiric therapy (broad spectrum)
- Definitive (or targeted) therapy (narrow-spectrum)
- Prophylactic therapy
What factors must be considered when choosing an appropriate antibiotic?
- Pt factors
- Pharmacological factors
- Microbiological factors
If a pt is immunocompromised, would a bacteriostatic or bactericidal antibiotic be more appropriate?
Bactericidal since bacteriostatic antibiotics depend on the pt’s immune sys to clear the bacteria.
These 4 pharmacological factors must be considered before choosing an appropriate antibiotic.
- Absorption
- Distribution
- Metabolism
- Excretion
What is antibiotic resistance?
When a bacteria that was previously able to be killed or inhibited by an antibiotic is no longer affected by it
How can we know that bacteria are resistant?
- Pt doesn’t respond to antibiotic therapy
2. Lab testing
Two methods to determine antibiotic resistance:
- Disk-diffusion method
2. Tube-dilution method
In the disk-diffusion method, what does a large zone of inhibition mean?
It means that the bacteria are more susceptible to the antibiotic.
Term for the lowest concentration of antibiotic that’ll prevent bacterial growth (using the tube-dilution method)
“Minimum Inhibitory Conc” (MIC)
This method of determining antibiotic resistance is useful for proper dosing.
Tube-dilution method
This method of determining antibiotic resistance is useful for determining whether antibiotic resistance is present or absent.
Disk-diffusion method
Using the MIC as a reference, what should the body fluid conc of the antibiotic be?
3-5x higher than the MIC.
A higher MIC indicates…
higher bacterial resistance
Bacteria “A” has an ampicillin MIC measured to be 8 ug/ml. Bacteria “B” has an ampicillin MIC measured to be 16 ug/ml. Which bacteria will be more susceptible (sensitive) to ampicillin?
Bacteria A
In the tube-dilution method, clear tubes mean…
growth inhibition
Tube-dilution method, cloudy tubes indicate…
growth
What do you use if, while knowing the identity of the bacteria, you need to initiate therapy BEFORE the MIC info is available?
Consult your local or regional “Antibiogram”
Three biological mechanisms of antibiotic resistance:
- Direct breakdown of antibiotic by bacterial enzymes.
- Promote excretion or prevent uptake of antibiotic
- Alter (or bypass) the target of the antibiotic
How do bacteria become resistant?
- Spontaneous mutation in DNA
2. Obtain new resistance genes
Where are resistant genes often found?
Plasmids
How’re plasmids transferred to other bacteria?
Conjugation
Spontaneous mutation and proliferation of resistant mutant is…
a) Vertical evolution
b) Horizontal evolution
a)
Plasmid transference and subsequent resistant bacteria is…
a) Vertical evolution
b) Horizontal evolution
b)
Continual exposure to an antibiotic creates a strong selective pressure on bacteria to become ______.
resistant
Where does the antibiotic selective pressure that causes bacterial resistance come from? (3)
- Ubiquitous non-human use of antibiotics
- Increased use/overuse of antibiotics in human medicine
- Pt non-compliance
What is MRSA?
Methicillin-resistant Staphylococcus aureus
How can antibiotic resistance be combatted?
- Find/develop new antibiotics to replace those lost to resistance
- Manage current antibiotics better
