Test media and quantitative method for identification and

Abstract

A test method and medium for quantitatively identifying and distinguishing biological materials in a test sample. A first biological material has enzyme specificity for a first chromogenic substrate, a second biological material has enzyme specificity for a second chromogenic substrate, and a third biological material has specificity for one of the substrates. The chromogenic substrates form respective first and second colored water insoluble compounds upon reaction with specific enzymes. The first and second biological materials are capable of fermenting a sugar, and the third material does not ferment sugar. The test medium is adjusted to a pH conducive for color change of a pH indicator upon acidification due to fermentation, resulting in the formation of a zone of a third color around the water insoluble compounds of the sugar-fermenting materials. The sample is incubated, and examined for the presence of colonies of the first biological material, having the first color and an encircling zone of the third color; for colonies of the second material, having the second color and the encircling colored zone; for colonies of a third material having the first color, and not having the colored zone; and for colonies having neither color, with or without the colored zone, representing colonies of other biological materials.