Question

Explain minimal inhibitory concentration (MIC)? Can MIC be determined using the disk diffusion method? What method is used to determine MIC?

Answer 1

In microbiology minimal inhibitory concentration (MIC) is the lowest concentration of antimicrobial drug that will inhibit the visible growth of the microorganism after overnight incubation.

Measurment of MIC by Agar disc diffusion method. In this well known procedure,agar plates are inoculated with a stanndardized inoculum of the test microorganism, then filter paper discs contaning the test compounds at the desired concentration are placed on the agar surface. The petri dishes are incubated under suitable condations.Generally antimicrobial diffuse in to the agar and inhibits the gerimination and growth of the test microorganisms and than the diameters of inhibition growth zones are measured.

Some other methods to measure MIC are.

Antimicrobial gradient method

Agar well diffusion method

Agar plug diffusion method

Cross streak method

Dilution methods(broth dilution method)

Time kill test