Minimum inhibitory concentration

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Minimum inhibitory concentration (MIC), in microbiology, is the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism after overnight incubation. Minimum inhibitory concentrations are important in diagnostic laboratories to confirm resistance of microorganisms to an antimicrobial agent and also to monitor the activity of new anitmicrobial agents.^[1]

MICs can be determined by "plain spotting" using a six-disc stamp that deposits dots of pre-impregnated filter paper onto the growth medium. The medium is then incubated for a period ranging from 15 to 24 hour, dependent on the microbe present. After incubation the areas of inhibition are measured using either a ruler, calipers, or a template. Another, more modern method is the E-test method using strips of a gradient of antibiotic concentration.

E-test strips create ellipses of microbial inhibition [1]. The point at which the MIC is taken within the ellipse of inhibiton is the point where the bacterial growth crosses the strip [2]

Clinically, the minimum inhibitory concentrations are used not only to determine the amount of antibiotic that the patient will receive but also the type of antibiotic used, which in turn lowers the opportunity for microbial resistance to specific antimicrobial agents.

[edit] References

1. ^ Andrews, J. M. Determination of minimum inhibitory concentrations. Journal of Antimicrobial Chemotherapy 48 (Suppl. 1):5-16, (2001). PMID 11420333.