Antimicrobial Therapies

Question Answer
What are the two main functions of Micro Lab? Diagnostic and Therapeutic
What does the diagnostic function of the micro lab entail? detection, isolation and identification of etiologic agents
What does the therapeutic function of the micro lab entail? antimicrobial susceptibility testing as guide to appropriate therapy
What is the fundamental principle of antimicrobial therapy? selective toxicity
What is an optimal agent? one with narrowest spectrum of activity, fewest side effects, and lowest toxicity.
How is the optimal agent administered? in dosage and schedule that will achieve a level at the site of infection equal to, or several times greater than, Minimum Inhibitory Concentration (MIC)
In reference to the individual patient, what must the Physician take into consideration? site of infection, age, status of kidney and liver function, pregnancy, hypersensitivity, Idiosyncracy, and drug interactions
What are the disavdantages of improper use of antimicrobials? Toxicity, drug resistance, alteration of indigenous flora, hypersensitivity
What are the purposes for antimicrobial suspectibility testing? Initiation of appropriate therapy, modification of existing therapy, and determination of susceptibility patterns in local environment
What are the two methods of antimicrobial susceptibility testing? Broth dilution and agar diffusion
Broth dilutions yield what value to be reported? MIC value
Agar diffusions yield what value to be reported? SIR value
What is an antibiogram? a species’ susceptibility pattern; useful as guide to empirical therapy
Broth dilutions must contain what two controls? Sterility control and growth control
In the broth dilution, how is the MIC determines? The MIC is that last tube without turbidity
What does MIC stand for? Minimum Inhibitory Concentration
What are the advantages of using a microtiter plate? easier handling, low volumes of reagent and microbe, convenience,and automated reading
How is a microtiter plate read? As inhibition of growth
On a microtiter plate, a button in the well indicates what? growth
What method is commonly used in agar diffusion susceptibility testing? Kirby-Bauer
What is the agar used in Kirby-Bauer? Mueller-Hinton agar
How many drugs can be tested at once on a Mueller-Hinton plate using the Kirby-Bauer method? 12
In the agar diffusion method, what does a larger zone of inhibition correlate to? Higher susceptibility to the drug
A result of ~6 mm for a zone of inhibition would correlate to what? Resistance to the drug
In the broth dilution technique, no turbidity in the tube means what? no growth
What are the 3 susceptibility test panels? Panel for GP and GN isolants Panel for specific species Example: P. aeruginosa Panel for urinary or CSF isolants
In the SIR interpretation, how does S correlate with the MIC value S (susceptible) = MIC < therapeutic concentration; expected to respond to agent at usual dosage and schedule
In the SIR interpretation, how does R correlate with the MIC value R (resistant) = MIC > achievable level by usual dosage and schedule
In the SIR interpretation, how does I correlate with the MIC value I (intermediate) = MIC ? expected level at site of infection by usual dosage and schedule; may respond to high dosage
When should the plate used for Kirby-Bauer be measured? After 16-18 hours of incubation
What size are the MH agar plates? 150 mm

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