Method and apparatus for determining the sensitivity of a microorganism to a growth altering agent

A method for determining the minimum concentration at which a growth-altering agent has an appreciable effect on the growth of a target microorganism, comprising the steps of:

• (a) providing a microorganism growth medium;
• (b) providing a sensible reagent, which includes a growth-altering agent mixed with a marker, said marker having a signal with a magnitude which is proportional to said marker's concentration;
• (c) incorporating said reagent into said growth medium, in a manner that creates a gradient of concentrations of said growth-altering agent and said marker within said growth medium;
• (d) inoculating said growth medium with said target microorganism;
• (e) incubating said inoculated growth medium for a period of time sufficient for said target microorganism to grow a detectable amount;
• (f) evaluating said growth medium for sections of said growth medium having appreciable differences in microorganism growth characteristics, said sections separated from one another by a boundary region;
• (g) measuring said magnitude of said marker signal in said boundary region;
• and
• (h) calculating said concentration of said growth-altering agent using said measured magnitude of said marker signal.

A method for determining the concentration at which a growth-altering agent has an appreciable effect on the growth of a target microorganism, comprising the steps of:

• (a) providing a microorganism growth medium having a sensible reagent that includes a growth-altering agent mixed with a marker, said marker having a signal with a magnitude that is proportional to said marker's concentration;
• (b) innoculating said growth medium with said target microorganism;
• (c) incubating said innoculated growth medium for a period of time sufficient for said target microorganism to grow a detectable amount;
• (d) determining a boundary region between a pair of contiguous sections of said growth medium having differences in microorganism growth;
• (e) sensing said marker signal in said boundary region;
• and
• (f) calculating a concentration of said growth-altering agent using said sensed marker signal.

An apparatus for determining a concentration at which a growth-altering agent has an appreciable effect on the growth of a target microorganism, comprising:

• a sheet of microorganism growth medium;
• and
• a sensible reagent that includes a growth-altering agent and a marker, said marker having a signal with a magnitude proportional to said marker's concentration;
• wherein said reagent is incorporated into said sheet of growth medium in a manner that creates a gradient of concentrations of said growth-altering agent and said marker within said growth medium.