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Minimum Inhibitory Concentration (MIC)


The MIC or minimum inhibitory concentration test determines antimicrobial activity of a material against a specific organism.

The most common methods are the tube dilution method and agar dilution methods. The tube dilution test is the standard method for determining measure of microbial resistance to an antimicrobial agent.

Serial dilutions of the samples are made in a liquid microbial growth medium which is inoculated with a prescribed number of organisms and incubated for a prescribed time. The lowest concentration (highest dilution) of sample preventing appearance of turbidity (growth) is considered to be the minimal / minimum inhibitory concentration (MIC). This dilution of the test agent is bacteriostatic.

The minimal bactericidal concentration or the minimum lethal concentration of an antibacterial which is defined as the maximum dilution of the product that will kill a test organism can be determined by subculturing last clear MIC tube onto growth medium and examining for bacterial growth. Serial dilutions are made of the products in bacterial growth media.

Zone of Inhibition

This is the disc diffusion method

It demonstrates activity / potency of antimicrobials or antibiotics by measuring the zone of inhibition against specific microorganisms. The test is applicable for materials treated with an antimicrobial agent that leaches out the material.