Podcast
Questions and Answers
What is the main difference between the Kirby-Bauer assay and the Etest method?
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. (correct)
- The Kirby-Bauer assay involves using plastic strips with antibiotic gradients, while the Etest method uses circular disks impregnated with antibiotics.
- The Kirby-Bauer assay produces an elliptical zone of inhibition, while the Etest method produces a circular zone of inhibition.
- The Kirby-Bauer assay allows concurrent comparison of multiple antimicrobials, while the Etest method does not.
How is the MIC determined using the Etest method?
How is the MIC determined using the Etest method?
- By measuring the diameter of the circular zone of inhibition around the plastic strips.
- By counting the number of bacterial colonies that grow around each plastic strip.
- By the color change of the bacterial cells in contact with the plastic strips.
- By observing the intersection of the elliptical zone with the gradient on the drug-containing strip. (correct)
Which method allows for the evaluation of multiple antimicrobials simultaneously on a single plate?
Which method allows for the evaluation of multiple antimicrobials simultaneously on a single plate?
- Dilution methods
- Kirby-Bauer assay
- Gram staining
- Etest method (correct)
Why is an elliptical zone of inhibition observed in the Etest method?
Why is an elliptical zone of inhibition observed in the Etest method?
What allows for direct comparison of MIC values of different antimicrobials using the Etest method?
What allows for direct comparison of MIC values of different antimicrobials using the Etest method?
How can researchers differentiate between different MIC values when using the Etest method?
How can researchers differentiate between different MIC values when using the Etest method?
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.
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Description
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.
