Abx Resistance: Relationship to Clinical Use Flashcards
A drug that kills or inhibits the growth of microorganisms
Abx
Implies that an antimicrobial will not inhibit bacterial growth at clinically achievable concentrations
Resistant
Implies that an antimicrobial will inhibit bacterial growth at clinically achievable concentrations
Susceptible
Lowest concentration of antimicrobial that inhibits growth of bacteria
Minimal inhibitory concentration
Concentration of an antimicrobial that kills bacteria
Minimal bactericidal concentration
MIC that is used to designate between susceptible and resistant
Breakpoint
How is MIC determined in test tubes?
100mcg/mL is given to test tubes through serial dilutions to 0.4 mcg/mL; a standard amount o bacteria is added and incubated; the lowest concentration of abx with no bacterial growth (cloudiness) is the MIC
How is MIC determined on a well plate, and what are some advantages?
1 bacterium tested on each plate; each row has serial dilutions of a distinct antibiotic
(many abx per plate, less reagent and bacteria needed)
How is MIC measures automatically?
Machine will photometrically measure growth for each antimicrobial concentration well; determines an MIC within 6-8 hours
What is an advantage of automated testing?
antimicrobial susceptibilities can be determined at the same time the organism is identified
Test that can determine only susceptible vs resistant and not an MIC.
Kirby-Bauer Disk diffusion
MIC test that is measuring the diameter of growth inhibition and comparing to a chart.
Kirby-Bauer Disk diffusion
Tests that can determine MICs directly.
agar dilution and E-test
MICs are _____ while susceptible and resistant are ______ determinations
relative; absolute
Susceptible or resistant: MIC is lower than the breakpoint
susceptible
Susceptible or resistant: MIC is higher than breakpoint
resistant
How is breakpoint determined?
arbitrarily designated by a committee
T/F: MICs between different antibiotics may be compared to determine efficacy or potency of antibiotic.
F: breakpoint is different for each antibiotic
Where are half of abx used in N America?
agriculture
Why do doctors overuse abx? (3)
Patient expectations; diagnostic uncertainty; time
What patients are high risk for abx resistance? (3)
Immunocompromised, hospitalized, invasive devices (central venous catheters)
T/F: Abx are the ONLY drug that have direct public health consequences for persons other than the one who received the abx.
T
Although different antibiotics select different bacteria, they can select phenotypes that have resistance to other drugs, too. These microbes are called:
multidrug-resistant (MDR) organisms
Linezolid and erythromycin inhibit
protein synthesis
