Final answer:
The E test is used to determine both the susceptibility of a microorganism to antimicrobial drugs and the minimum inhibitory concentration (MIC) but not the minimum bactericidal concentration (MBC). This method combines elements of the Kirby-Bauer test and dilution methods.option 3 is correct.
Step-by-step explanation:
The E test is designed to determine the susceptibility of a microorganism to various antimicrobial drugs and allows for the determination of the minimum inhibitory concentration (MIC) but not the minimum bactericidal concentration (MBC). It is a method that combines aspects of the Kirby-Bauer disk diffusion test and dilution methods.
In an E test, a plastic strip with a gradient of antibiotic concentration is placed onto an agar plate that has been inoculated with a bacterial sample. An elliptical zone of inhibition develops around the strip, and where this zone intersects the gradient on the strip indicates the MIC. This helps in selecting appropriate antimicrobial therapy, but to obtain the MBC, additional tests like the tube dilution method are needed after MIC determination.