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This is when an organism is affected by the inhibitory action of an antimicrobial
susceptibility
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this is the ability of an organism to withstand the inhibitory effects of antimicrobials.
resistance
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this term is synonymous with antimicrobial agent.
antibiotic
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this is a natural or synthesized substance used to inhibit or kill infecting pathogens.
antibiotic (antimicrobial agent)
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what are the four types of susceptibility testing?
- Disk-diffusion test
- Broth dilution
- Agar dilution
- Specific resistance test
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these are a battery of filter paper disks that are impregnated with an antimicrobial agent. They are placed in an agar medium and incubated.
disk diffusion test
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Disk diffusion tests have to follow what guidelines?
CLSI
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disk diffusion tests are limited to ______ growers.
rapid
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what are the special requirements to test for strep on a disk diffusion test?
MH + 2-5% horse blood
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what are the special requirements for neisseria on a disk diffusion test?
5-7% CO2 and MH + 2-5% horse blood
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what medium is required to test for H. influenzae with a disk diffusion test?
Haemophilus test medium
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what special requirements are needed to test for N. gonorrhoeae with a disk diffusion test.
GC agar + CO2
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this is the smallest amount of medication required to inhibit growth.
Minimum inhibitory concentration (MIC)
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what unit of measurement is used for Minimum inhibitory concentration (MIC)?
ug/ml
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Minimum Inhibitory Concentration is correlated with what test?
disk diffusion test
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This is part of a broth dilution test?
Minimum inhibitory concentration
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what was developed to standardize the Kirby-Bauer System?
Minimum Inhibitory Concentration
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this has the same principle as the broth MIC but the agent is implanted into usually six medias.
MIC agar version
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which version of MIC is labor intesnive?
MIC agar version
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what is an advantage of the MIC agar version?
- can test multiple isolates per plate
- fastidious organism
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what technique should be used when streaking a MIC agar?
sprial technique
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what are the two automation techniques used for MIC testing?
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this is the lowest concentration that kills 99.9% of organisms
Minimum Bacterial Concentration
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in Minimum bacterial concentration, samples from _____ and higher are cultured.
MIC
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Minimum Bacterial Concentration is a _____________ procedure, not routine.
quantitative
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Minimum bacterial concentration is used for what patients?
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thest tests an enzyme that binds to beta lactam ring.
beta lactamase test
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beta lactamase test is similar to what?
cephalosporins
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what are the two enzyme conversions in the beta lactamase test?
- penicillin to penicilloic acid
- cephalosporins to cephalosporanic acid
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this is an in vitro test, which tests patient's serum against patient's own infecting organism.
schlichter's test
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in which susceptibility test do you collect two samples (peak and trough) which are placed on ice.
schlichter's test
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when is the trough sample collected for schlichter's test?
0-30 min before dose
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for IV when is the peak sample collected for schlichter's test?
30-60 minutes after dose
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for IM when is the peak sample drawn for schlichter's test?
60 minutes after dose
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for oral when is the peak sample drawn for schlichter's test?
90 minutes after
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what are the three indications of susceptibility testing?
- effectiveness of antimicrobial
- aid for clinicians
- ID organism
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what are two deficiencies of susceptibility testing (KBS)?
- qualitative
- some inaccuracies
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what are four factors for antimicrobial selection?
- hospital formulary
- medical staff
- CLSI
- similar activity
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this is the size of an area arounds disc that prevents growth, measured in mm.
zone of inhibition
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zone of inhibition is based on previous _____ patterns.
MIC
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this is an antibiotic agar diffusion method where concetration decreases as distance increases.
modified kirby-bauer principle
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what media is used for a modified kirby-bauer?
mueller-hinton agar
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a pH outside of 7.2-7.4 alters what two things on a modified kirby-bauer?
- antibiotic activity
- size of zone
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a 150mm plate will have how much medium which produces what depth?
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a 100mm plate will have how much medium which producesw what dpeth?
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true or false
MH plates should be incubated for 10-20 minutes before using the media to evaporate excess moisture.
true
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antimicorbial disks are made out of ____________ and supplied in cartridges.
filter paper
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how are antimicrobial discs stored?
refrigerate unopened at 4-8oC
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which two antimicrobial discs should be frozen at -20oC?
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doing this prior to use will minimize condensation on antimicrobial discs.
warm 1-2 hours prior to use
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what standard should be used to control inoculum size.
McFarland standard
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how many isolates should be used to inoculate broth in inoculum preparation?
4 or 5
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when performing susceptibility testing you should alternate _______ prep/suspension.
saline
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for saline prep/suspension 4-5 colonies should be placed in what percent NaCl.
0.85%
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susceptibility testing suspension should not sand longer than ________ minutes.
15-20
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insufficient inoculum in susceptibility testing could create a false ______ zone.
large
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too heavy susceptibility testing coul cause a false _____ zone.
small
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when performing plate inoculation for susceptibility testing, a ___ direction mat-streak should be used.
3
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how long should a plate inoculation for susceptibility testing be allowed to dry? no more than?
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a 150mm plate can hold how many antimicrobial disks?
12 disks
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a 100 mm plate can hold how many antimicrobial disks
5 disks
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how far should antimicrobial disks be placed from each other (center to center)?
24 mm
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how far should antimicrobial disks be placed from the edge of the plate?
15mm
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plates that have been inoculated should be incubated within ___ minutes.
15
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CO2 should be avoided in inoculated plates except for what three genuses?
- Neisseria
- Haemophilus
- Streptococcus
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when reading inoculated media, reflected light should be used in what two situations?
- for most organisms
- blood containing plates
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when reading inoculated media, transmitted light should be used when?
haze from staph and enterocci
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what are the three results for susceptibility testing?
- susceptible (sensitive, inhibited)
- resistant (not inhibited)
- intermediate (may require higher concentration of antibiotics)
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what are the four(ATCC standard control strains for susceptibility testing.
- Pseudomonas aeruginosa
- Streptococcus faecalis
- E. coli
- S. aureus
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guidelines for susceptibility testing quality control are provided by who?
CLSI
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this is a quantitative dilution test using microtube wells.
MIC
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what are the three steps for the MIC procedure?
- ioculate
- incubate
- interpret
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how is growth interpreted on MIC?
large button or turbidity
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the MIC is the ______ tube for no growth.
first
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