microbiology lab day 8 part 1 (kirby-bauer test, MIC, microbiostatic, MBS, antibiotics, phenol coeff
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In the kirby-bauer test, what do the disks do?
antibiotics diffuse slowly from the disks to the agar plates
in the k-b test, what type of chemical do the disks contain?
During the k-b test, if one sees a zone of inhibition, what does that mean?
the bacterium is senstitive to this antibiotic
How is the k-b test conducted?
Bacterium is plated using a spread-plate technique and then antibiotic disks are stamped onto the plate. Then the plate is innoculated and examined for zones of inhibition
what is MIC?
minimum inhibitory concentration. The minimal concentration of an antibiotic that inhibits the growth of a bacterium
what is a microbiostatic chemical?
an inhibitory chemical
If a bacterium has a very high MIC for a particular antibiotic, what would one see around this particular a.b.'s disk in the k-b test if this bacterium was used?
either no zone of inhibition or a very small zone of inhibition
What is MBS efficiency?
the ability to deter a bacterium's growth by using a particular MBS agent
How is MBS efficiency determined
It is determined with regard to the phenol coefficient
what is the phenol coefficient?
(highest dilution (i.e. lowest concentration) of antimicrobial of interest)/(highest dilution of phenol with same microbicidal results)
the Etest is convenient for use with _____ _____
How is the Etest conducted?
a petri dish containing the proper agar is streaked in three different directions with the test bacterium and special plastic Etest strips are placed onto the surface so that they extend out radially from the center. Each strip represents a different antibiotic and it contains a gradient of the antibiotic