Method for rapid quantification of microorganism growth

A method to count microbial colonies growing on an inoculated growth medium adhered to a substantially planar culturing device comprising the steps of:

• a) obtaining a filtered mask image of the culturing device to identify pixels in the mask image which lie outside of the inoculated growth medium in order to prevent processing of pixels which lie outside of the growth medium;
• b) obtaining a filtered noise image of the culturing device to identify pixels in the filtered noise image having measured intensities outside of a predetermined range of intensities and which lie inside of the growth medium in order to prevent processing of pixels having measured intensities outside of a predetermined range of intensities which lie inside of the growth medium;
• c) obtaining a filtered background image of the culturing device to provide background image data which excludes pixels identified in steps a) and b);
• d) incubating the inoculated growth medium for a selected time interval;
• e) obtaining a first filtered image of the culturing device to provide first image data;
• f) processing the background and first image data to produce a difference image wherein the difference image is obtained by taking a difference between the first filtered image data and the background image data;
• g) processing the difference image to identify hit pixels which are local maxima, wherein a hit pixel is determined by the steps of:
• 1) testing a pixel value at a center pixel for compliance with a value;
• 2) testing at least two neighboring pixel values directly adjacent to the center pixel to insure that the immediate neighboring pixels have values less than the center pixel value;
• 3) testing pixels adjacent to each of the neighboring pixels of step 2) which are neighbors once removed to the center pixel to insure that they have a value less than the value of an adjacent neighboring pixel;
• and
• 4) labeling each center pixel which satisfies the tests of steps 1), 2) and 3) as a hit pixel;
• and
• 5) clustering the hit pixels by dilating each of the hit pixels to encompass a matrix and expanding the matrix to encompass hit pixels which overlap one another wherein a number of matrices on the growth medium corresponds to a number of microbial colonies in the growth medium;
• h) storing a position and number of matrices which correspond to a count of the microbial colonies in the growth medium;
• and
• i) providing a count of the microbial colonies in the growth medium.