METHOD AND APPARATUS FOR DETERMINING THE SENSITIVITY OF A MICROORGANISM TO A GROWTH ALTERING AGENT

A method and an apparatus for determining the concentration at which a growth-altering agent has an appreciable effect on the growth of a target microorganism are provided. The method comprises the steps of (a) providing a microorganism growth medium; (b) providing a sensible reagent, which includes a growth-altering agent mixed with a marker that has a signal with a magnitude proportional to the concentration of the marker; (c) incorporating the sensible reagent into the growth medium, in a manner that creates a gradient of growth-altering agent and marker concentrations within the growth medium; (d) inoculating the growth medium with the target microorganism; (e) incubating the inoculated growth medium for a period of time sufficient for the target microorganism to grow a detectable amount; (f) evaluating growth characteristics of the microorganism in a region containing the growth-altering agent, (g) measuring the magnitude of the marker signal in that region; and (h) determining the concentration of the growth-altering agent using the measured magnitude of the marker signal.