Clinical Use of Abx Flashcards
Describe why endocarditis is considered to be in a protected local environment. Tx?
fibrin/platelet mixture protects from host defense mechs; bactericidal therapy
Describe why intracellular infections are considered to be in a protected local environment. Tx?
some bugs thrive intracellularly; need to penetrate these cells eg rifampin, tetracycline, erythromycin
What is a consideration for drugs and the bladder? What drugs should be used?
- some drugs concentrate there, changing susceptibility - quinolones as a group are good EXCEPT moxifloxacin
What does susceptible (S) mean?
bacteria will probably respond to the Abx
Describe why abscesses are considered to be in a protected local environment. Tx?
drugs can’t penetrate; need surgical drainage
Name 3 susceptibility tests.
- broth dilution 2. disk diffusion (Kirby-Bauer) 3. E test
What is the MBC?
the lowest conc of the Abx that kills 99.9% of the initial inoculum
_____ Abx have MBC concentrations many fold higher than the MIC concentration.
Bacteriostatic
What is the MIC?
the lowest concentration of Abx that prevents visible bacterial growth
Bacteriostatic Abx have MBC concentrations ____ than the MIC concentration.
many fold higher
Describe why meningitis is in a protected local environment. Tx?
within the BBB and protected from host defense mechs; bactericidal therapy
What does resistance (R) mean?
infection will probably not respond to the Abx
What is the E test?
strip containing a gradient of Abx is plated with a bug- clearing makes ellipse shape- where ellipse point meets the strip is the MIC
At ____, the Abx should have a maximal serum conc that exceeds the MIC of the bacteria (Cp>MIC).
normal doses
What is the MBC used to determine?
bactericidal vs bacteriostatic
Bacteriostatic Abx have _____ many fold higher than the MIC concentration.
MBC concentrations
What is broth dilution?
serial dilutions of Abx in liquid medium that are inoculated with standard #s of bugs- incubated- check growth- look at lowest conc of Abx that prevented growth (MIC)
What does MIC stand for?
minimum inhibitory concentration
Describe why foreign bodies are considered to be in a protected local environment. Tx?
they impair host defense mechs and promote attachment/biofilms; remove the foreign body
What does MBC stand for?
minimum bactericidal concentration
At normal doses, the Abx should have a _____ that exceeds the MIC of the bacteria.
maximal serum conc
How should a chemo pt’s bacterial infection be treated and why?
with bactericidals bc they have decreased neutrophils
What does intermediate (I) mean?
indeterminate or uncertain response given standard dosing
Describe why bone infections are considered to be in a protected local environment. Tx?
protected from opsonophagocytosis; prolonged therapy with drugs that concentrate in bone eg fluoroquinolones
When would you use empiric therapy?
- life threatening infections 2. outpatient tx
What local factor considerations should be made before giving an Abx to a pt?
- distribution 2. protected local environments 3. the bladder 4. daptomycin and pulmonary surfactant
Bactericidal Abx have _____ that are equal to or barely higher than the MIC.
MBC concentrations
What is the relationship btw daptomycin and S. pneumoniae?
does not treat well bc it’s inactivated by pulmonary surfactant
At normal doses, the Abx should have a maximal serum conc that exceeds the ____ of the bacteria.
MIC
What is an antibiogram?
a yearly summary of local susceptibility patterns for common pathogens
_____ Abx have MBC concentrations that are equal to or barely higher than the MIC.
Bactericidal
What does Susceptible-dose dependent (SDD) mean?
susceptibility depends on dosing regimen (need higher drug exposure)
Bactericidal Abx have MBC concentrations that are ______ than the MIC.
equal to or barely higher
What is the disk diffusion/Kirby-0Bauer test?
suspension of bug is plated and Abx disks placed on top- look for diameter of clearing around the disk
What 7 host factors need to be considered when giving a drug to a pt?
- hx of reactions to Abx 2. renal/liver function 3. age (fetus/neonates/young children) 4. genetic/metabolic factors (G6PD, diabetes) 5. pregnancy 6. drug interactions 7. immune status
What is empiric therapy?
initiation of therapy before a specific diagnosis is made
