Lecture 10 2/22/24 Flashcards
How does an antibiotic differ from an antimicrobial?
-antibiotics specifically target bacteria
-antimicrobials are a broader class that act on microbes in general
What is minimum inhibitory concentration?
lowest drug concentration that inhibits bacterial growth
What is minimum bactericidal concentration?
lowest drug concentration that kills 99.9% of bacteria
Which datapoints are used to determine pharmacological breakpoints?
-pharmacokinetic data
-pharmacodynamic data
-clinical outcomes
-epidemiologic data
Who determines pharmacological breakpoints?
Clinical and Laboratory Standards Institute
Which critically important antimicrobials are highest priority?
-quinolones
-3rd gen. + cephalosporins
-macrolides/ketolides
-glycopeptides
-polymyxins
Which high priority critically important antimicrobials are commonly used in vet med?
-quinolones
-cephalosporins
-macrolides
What are the main clinical signs of infection?
-pyrexia/fever
-leukocytosis
-inflammation
-neutropenic fever
What evidence suggests infection?
-direct microscopic examination
-cytology
-gram staining
Which infections will not require use of antibiotics?
-certain chronic infections
-abscesses
-cases with economic constraints
In which situations should you address underlying factors instead of treating with antibiotics?
-situations that favor infection relapse
-group settings that contribute to spread of infection
What are the consequences of prescribing antibiotics just in case?
-add to cost
-diarrhea/vomiting
-adverse reactions
-drug interactions
-select for bacterial resistance
What factors should be considered when selecting an antibiotic?
-causative organism
-physiologic status of the patient
-cost/route/frequency of administration
Why is it important to understand the nuances of the infection site?
-clues on organism involved
-clues on drug disposition features required
-clues on local host factors
Why is it important to gram stain?
there are important pathophysiology and endotoxin differences between gram pos. and gram neg.
Why is it important that gram neg. bacteria have an LPS outer layer?
LPS creates challenges for antimicrobial efficiency
When is empirical therapy used?
-organism and susceptibility pattern can be reasonably estimated
-life-threatening infections
When is objective therapy used?
when culture and susceptibility data is available
What is a breakpoint?
-specific MIC of a drug selected to predict a clinical outcome
-for a specific pathogen, disease, species, and regimen
What are the interpretations of MIC?
-susceptible
-intermediate
-resistant
Which standardized tests can be used to determine MIC/breakpoints?
-disk diffusion
-E-test
-broth dilution
What is important to consider regarding culture/susceptibility testing and actual use of antimicrobials?
-breakpoints are variably correlated with clinical efficacy
-penetration in target tissue may impact efficacy
What percent of time must be spent above MIC for a time-dependent antimicrobial treating a gram pos. bacteria?
50% of dosing interval must be above MIC
What percent of time must be spent above MIC for a time-dependent antimicrobial treating a gram neg. bacteria?
100% of dosing interval must be above MIC
What concentration must a concentration-dependent antimicrobial reach in order to be effective?
8-10x MIC once
What must be considered when deciding on dose?
-whether or not the label dose is still appropriate
-antibiotic PD profile
-infection location
What is the SPACED acronym?
-spectrum
-PK/PD
-adverse reactions
-compliance
-environment
-diagnostics
