Principles of Antimicrobial Therapy Flashcards
(26 cards)
What is the primary goal of antimicrobial therapy?
to kill the infectious organism WITHOUT harming the host
What is the difference between empiric, definitive and prophylactic antimicrobial therapy.
Empiric: when you give a pt an Abx because you THINK they have an bacterial infection
Definitive: when you give a pt an Abx because you KNOW they have an bacterial infection
Prophylaxis: Give an Abx to PREVENT a bacterial infection
What ranges between the dose necessary to inhibit/kill infectious organism and the dose that causes harm to the patient?
Selective Toxicity
What refers to the # and variety of infectious organism the drug is active against?
Spectrum of activity
What is the difference between bactericidal and bacteriostatic antibiotics?
- Bactericidal: cause DEATH and disrupt the bacterial cell
* Bacteriostatic: inhibit bacterial replication without killing
Post antibiotic effect?
Continued growth suppression of infectious organism AFTER drug levels in body have fallen below effective concentrations
What is the lowest concentration of drug required to inhibit visible growth of infectious organism?
MIC (minimum inhibitor concentration):
When must a bactericidal antimicrobial agent be used?
In immunosuppressed patients
What are the common side effects of antimicrobial agents?
• Allergy/hypersensitivity: immediate (IgE mediated) vs. delayed
• Alterations in normal microbial populations
o GI (diarrhea) and vaginal (yeast infections)
o More common with broad spectrum drugs
• Patients are at risk to develop superinfections (Clostridium difficile)
•Optimal therapy should exhibit __________ toxicity
o target differences between microorganism & host
o target should be critical to survival & replication of the microorganism
SELECTIVE
Which target is most unique to the infecting organism? A. Cell wall synthesis B. Cell membrane C. Protein synthesis D. DNA synthesis E. Folic Acid Metabolism
A
What is the dose that just kills the bug?
Therapeutic dose
What is the dose that kills the bug and causes host toxicity?
Toxic dose
[SATA] Which of the following have HIGH therapeutic index? A. Erythromycin B. Penicillins C. Amioglycosides D. Cephalosprorins E. Chloramphericol
B, D
[SATA] Which of the following have INTERMEDIATE therapeutic index? A. Erythromycin B. Penicillins C. Amioglycosides D. Cephalosprorins E. Chloramphericol
A, E
[SATA] Which of the following have LOW therapeutic index? A. Erythromycin B. Penicillins C. Amioglycosides D. Cephalosprorins E. Polymixin
C, E
Which drugs do you expect to be more toxic to the patient?
Drugs with low TI
What does BROAD spectrum of activity mean?
active against a LARGE variety of infectious organisms (Gram negative, gram positive AND atypicals)
What does a NARROW spectrum of activity mean?
active against SMALL number of species
•Only good for gram negative OR gram positive OR atypicals
Where do bactericidal drugs generally act?
on the cell wall, cell membrane or DNA
Where do bacteriostatic drugs generally act?
on the protein synthesis
Explain Time Dependent Killing.
• “slow” cidal action
• Maximum killing depends on how long the concentration is maintained above MIC
o Achieved by continuous infusion or frequent dosing
o Increasing concentrations does not increase killing
Explain Concentration Dependent Killing.
• Rate and extent of killing increases with increasing concentration
• Peak plasma concentration to MIC ratio is important
o Higher doses with extended dosing intervals
The mechanism of post antibiotic effect is not clear but may relate to . . .
o Time it takes the infecting organism to synthesize new cellular components
o Persistence of drug at target
o Infecting organism becomes more susceptible to host defenses
