Microbial Susceptibility Test Epsilometry A method to determine microbial susceptibility to antibiotics in which a plastic strip impregnated with the antibiotic of interest is placed on an agar plate that has been inoculated with bacteria. The antibiotic diffuses from the strip producing a concentration gradient of drug on the agar. The point at which the elliptical shaped area of growth inhibition meets the strip is the minimum inhibitory concentration of the drug of interest. Epsilometry E-Test EPSILOMETER E-test (Epsilometry)