Minimum Inhibitory Concentration Test - MIC Test (With Photos)

Minimum Inhibitory Concentration Test : MIC Test

Microtiter MIC Test -

Note: The MIC test is an established "screen" for the biostatic (and possibly also biocidal) activity of liquid antimicrobials. It is rapid, relatively inexpensive, reliable, and straightforward. Care must be taken not to confuse "kill" with inhibition of microbial growth, however, when interpreting MIC test results.

Summary of the Minimum Inhibitory Concentration Test (MIC Test):

	A pure culture of a single microorganism is grown in Mueller-Hinton broth, or other broth as appropriate.
	The culture is standardized using standard microbiological techniques to have a concentration of very near 1 million cells per milliliter. The more standard the microbial culture, the more reproducible the test results.
	The antimicrobial agent is diluted a number of times, 1:1, through a sterile diluent (usually Mueller-Hinton broth).
	After the antimicrobial agent has been diluted, a volume of the standardized inoculum equal to the volume of the diluted antimicrobial agent is added to each dilution vessel, bringing the microbial concentration to approximately 500,000 cells per milliliter.
	The inoculated, serially diluted antimicrobial agent is incubated at an appropriate temperature for the test organism for a pre-set period, usually 18 hours. The more standard the incubation period, the more reproducible the test results.
	After incubation, the series of dilution vessels is observed for microbial growth, usually indicated by turbidity and/or a pellet of microorganisms in the bottom of the vessel. The last tube in the dilution series that does not demonstrate growth corresponds with the minimum inhibitory concentration (MIC) of the antimicrobial agent.

Strengths of the Minimum Inhibitory Concentration Test (MIC Test):

	The MIC test is relatively straightforward and easy to prepare for and execute, which naturally enhances reproducibility.
	The MIC test can be done on a very small scale (microtiter MIC).
	The MIC test is an easy way to test the antimicrobial attributes of a formulation across many different parameters, such as across microbial species or surfactant blends.
	Because little preparation is required for the minimum inhibitory concentration testing, test turnaround times can be kept low.

Weaknesses of the Minimum Inhibitory Concentration Test (MIC Test):

	Minor variations in the way MIC test parameters can have major impacts on the apparent MIC. For example, extended incubation will make the MIC appear to be higher, and lower inoculum concentrations will make the MIC appear to be lower.
	Results from MIC studies must be kept and considered in the appropriate context. In the tube corresponding to the MIC, microorganisms were merely prevented from growing and not necessarily killed - there could still be 500,000 viable cells in that dilution vessel just waiting to grow should the antimicrobial agent become neutralized!

MIC tests are an important and unique part of Antimicrobial Test Laboratories' portfolio of testing services. MIC tests are especially appropriate if liquid antimicrobial agents will be used to inhibit the growth of microorganisms in some context.

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