May 26

Accurate MIC endpoints with automation

LGC’s drug development team regularly assess new methods to refine and strengthen our existing analytical services across all disciplines.


An old-school stalwart of microbiology testing, minimum inhibitory concentration (MIC) testing identifies the lowest concentration of a substance that prevents visible growth of a bacterial strain.


The MIC is the bacteria’s tipping point and is the mainstay of in vitro antimicrobial susceptibility testing (AST) for any new antimicrobial drug or treatments or for monitoring the emergence of resistant strains against existing antibiotics.




At LGC,MIC testing is done in line with CLSI M100-S27E Performance Standards for Antimicrobial Susceptibility Testing (2017) and CLSI M07-A10 (2015) using a MIC endpoint broth microdilution test. A serial dilution of an antimicrobial stock solution is dispensed into microtitre plates. Bacterial suspensions are made in broth culture to a standard density of colony forming units (cfu) this is then added to the plates and the effect on growth observed. The same test can be repeated for multiple culturable bacteria with multiple antimicrobials and the MICs compared.


Traditionally these measurements are done by eye, but optical density readings (OD600) to determine MIC endpoints are a promising alternative – reducing error and time and permitting high-volume screening in the laboratory.


Download our poster on “Alternative Minimum Inhibitory Concentration (MIC) Test Methods: The Use of Optical Density Readings to Determine an MIC Endpoint” to read more about the results from side-by-side comparisons of visual MIC testing with automated endpoint determination on a range of aerobic bacteria and antibiotics.


Alternative Minimum Inhibitory Concentration (MIC) Test Methods poster

Authors; April Taylor, Scientist, LGC and Ed Siegwart, Senior Scientist, LGC


To find out more about our anti-infective drug development and surveillance expertise, please contact us




Leave a Reply

%d bloggers like this: