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10 Cards in this Set
- Front
- Back
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In what circumstances can an antibiotic falling in the 'intermediate' category of antimicrobial resistance be used to treat an infection due to a specific isolate?
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Such an antibiotic can be used if the patient can tolerate high doses, or if the infection is in an anatomic site where the antibiotic is concentrated, such as a beta-lactam in the urine.
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What organization establishes recommendations for antimicrobial testing?
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The Clinical and Laboratory Standards Institute (CLSI). Previously, this organization was known as the National Committee for Clinical Laboratory Standards (NCCLS).
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The CLSI provides a list of antimicrobial agents that should be considered for testing against commonly-isolated bacteria. State the antibiotic to be tested against the following beta-lactam bacteria.
Staphylococcus a nd Streptococcus Enterococci and Enterobacteriaceae Staphylococcus Enterococci (some institutions) |
Test penicillin for Staphylococcus and Streptococcus.
Test ampicillin for Enterococci and Enterobacteriaceae. Test oxacillin against Staphylococcus. Test vancomycin against enterococci at institutions where resistance is suspected or has occurred. |
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Define minimum inhibitory concentration (MIC).
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MIC is the lowest concentration of an antimicrobial that will inhibit visible growth.
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What three methods are used to determine MIC?
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The three main methods of determining MIC are the dilution test, the disk diffusion test, and the Etest. Although microdilution systems now provide more rapid results and are more efficient, Henry stresses the continued utility of the disk diffusion test.
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What culture medium is recommended for antimicrobial testing of aerobic and facultative anaerobic bacteria?
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The Mueller-Hinton medium is the CLSI recommendation.
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What is the concentration of McFarland suspension used for agar disk diffusion?
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CLSI recommends a 0.5 McFarland suspension for disk diffusion.
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The original VITEK automated antimicrobial susceptibility system measured only turbidity to assess resistance. What parameters does the Vitek II analyze?
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The Vitek II still measures turbidity, but also uses a multichannel fluorometer and photometer to record fluorescence and colorimetric data every 15 minutes.
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Define minimum bactericidal concentration (MBC).
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The minimum bactericidal concentration (MBC) is defined as the lowest concentration of antimicrobial agent that is bactericidal or lethal to at least
99.9% of the original inoculum. |
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How well does the serum bactericidal test correlate with the outcome of antimicrobial therapy?
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It does not correlate well with outcome, and its utility has been questioned.
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