Gradient strip minimum inhibitory concentration (MIC)

Registry Details

Area Health Science
Lab name Antibiotic Reference Laboratory
Lab location Kenepuru Science Centre, Porirua
Test name Gradient strip minimum inhibitory concentration (MIC)
Organisms Aerobic or facultative bacteria
Requested for surveillance no
Notice required no
Routine turnaround time 4 working days for reference specimens
Culture requirements Pure culture
Media requirements A slope of any medium that supports the growth of the organism
Pre-transport requirements Ambient temperature
Transport requirements Ambient temperature
Unacceptable sample types Clinical specimens will not be accepted.
How results reported MIC (mg/L) and interpretation according to CLSI interpretive standards
Referral link Form


In this test, a preformed antimicrobial gradient from the Etest strip diffuses into the agar medium inoculated with the test organism. The MIC is read directly from the scale printed on the Etest strip at the point where the ellipse of the growth inhibition intercepts the strip. An Etest MIC value that falls between the conventional two-fold dilutions is rounded up to the next two-fold dilution value before interpretation.