Patent ID: 8647859

Claim:
A method for discriminately analyzing a Gram-positive bacteria and a Gram-negative bacteria contained in a sample by using at least one flow cytometer, the method comprises computer-executable steps performed by a processor of a computer system to implement: obtaining first and second signals of a quantity of the sample which are indicative respectively of first and second optical characteristics of the Gram-positive bacteria and the Gram-negative bacteria; scaling the obtained first and second signals onto a two-dimensional scale, wherein the first and second optical characteristics are scalable respectively along two axes of the two-dimensional scale; defining a first two-dimensional threshold to delineate, on the two-dimensional scale, a first region within which both the Gram-positive bacteria and the Gram-negative bacteria are empirically determined likely to exhibit their first and second optical characteristics; applying the first two-dimensional threshold to the first and second signals scaled onto the two-dimensional scale to derive a first count indicative of a number of the Gram-positive bacteria and the Gram-negative bacteria countable within the first region on the two-dimensional scale; obtaining third and fourth signals of another quantity of the sample, from the flow cytometer which are indicative respectively of the first and second optical characteristics of the alkaline treated Gram-positive bacteria and Gram-negative bacteria, wherein another quantity of the sample is treated with an alkaline solution that can cause different degrees of change to at least one of the first and second optical characteristics between the Gram-positive bacteria and the Gram-negative bacteria; scaling the detected third and fourth signals onto the two-dimensional scale; defining a second two-dimensional threshold to delineate, on the two-dimensional scale, a second region inside which the alkaline treated Gram-positive bacteria are empirically determined likely to exhibit their first and second optical characteristics and outside which the alkaline treated Gram-negative bacteria are empirically determined likely to exhibit their first and second optical characteristics; applying the second two-dimensional threshold to the third and fourth signals scaled onto the two-dimensional scale to derive a second count indicative of a number of the alkaline treated Gram-positive bacteria countable within the second region on the two-dimensional scale; and calculating on the first count and the second count to present a criterion for determining whether the specimen contains the Gram-positive bacteria or the Gram-negative bacteria.