6 Questions
What is the main difference between the Kirby-Bauer assay and the Etest method?
The Kirby-Bauer assay uses circular disks impregnated with antibiotics, while the Etest method uses plastic strips containing a gradient of antibiotics.
How is the MIC determined using the Etest method?
By observing the intersection of the elliptical zone with the gradient on the drug-containing strip.
Which method allows for the evaluation of multiple antimicrobials simultaneously on a single plate?
Etest method
Why is an elliptical zone of inhibition observed in the Etest method?
Due to the direct relationship between drug diffusion rate and concentration.
What allows for direct comparison of MIC values of different antimicrobials using the Etest method?
Placing multiple strips containing different antimicrobials on the same plate.
How can researchers differentiate between different MIC values when using the Etest method?
By comparing the intersection points of different elliptical zones with their respective drug gradients.
Study Notes
Comparing Kirby-Bauer Assay and Etest Method
- The main difference between the Kirby-Bauer assay and the Etest method is the way the Minimum Inhibitory Concentration (MIC) is determined: the Kirby-Bauer assay provides a qualitative result, while the Etest method provides a quantitative result.
MIC Determination using Etest Method
- In the Etest method, the MIC is determined by observing the point where the ellipse intersects the MIC scale on the strip.
- The MIC value is read at the point where the inhibition ellipse edge intersects the strip.
Evaluating Multiple Antimicrobials
- The Etest method allows for the evaluation of multiple antimicrobials simultaneously on a single plate.
Elliptical Zone of Inhibition
- An elliptical zone of inhibition is observed in the Etest method because of the continuous concentration gradient of the antibiotic on the strip.
Direct Comparison of MIC Values
- The Etest method allows for direct comparison of MIC values of different antimicrobials because the strips have a standardized MIC scale.
Differentiating MIC Values
- Researchers can differentiate between different MIC values when using the Etest method by reading the MIC value at the point where the ellipse intersects the MIC scale on the strip.
Learn about the Etest method, which is used to determine the Minimum Inhibitory Concentration (MIC) of antibiotics. This method combines elements from the Kirby-Bauer assay and dilution methods, where plastic strips with a gradient of antibiotics are placed on an agar plate inoculated with bacteria.
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