Method test media and chromogenic compounds for identifying and differentiating general coliforms and Escherichia coli bacteria

A method for testing the presence of and quantitatively identifying and differentiating general coliforms and E. coli in a test sample, said method comprising the steps of inoculating a test medium capable of forming a solid matrix or solid surface with said test sample to be tested for the presence of general coliforms or E. coli said test medium comprising a chromogenic .beta.-galactosidase substrate capable of forming a first water insoluble precipitate of a first color upon reacting with .beta.-galactosidase, a chromogenic indolyl .beta.-glucuronidase substrate capable of forming an insoluble precipitate of a second color contrasting with said first color upon reacting with .beta.-glucuronidase, and a nutrient base medium, wherein said indolyl .beta.-glucuronidase is at least one selected from the group consisting of 6-chloroindolyl-.beta.-D-glucuronide, 4,6-dichloroindolyl-.beta.-D-glucuronide, 6,7-dichloroindolyl-.beta.-D-glucuronide, 4,6,7-trichloroindolyl-.beta.-D-glucuronide and salts thereof, and

• incubating said test medium as a solid to produce colonies of said general coliforms and E. coli and said first and second colored precipitates corresponding to said colonies, and enumerating said colonies.

A method for testing the presence of and quantitatively identifying and differentiating general coliforms and E. coli in a test sample, said method comprising the steps of

• inoculating a solid or gel test medium with a sample to be tested for the presence of general coliforms or E. coli, said solid test medium comprising a chromogenic indolyl .beta.-galactosidase substrate capable of forming an insoluble precipitate of a first color upon reacting with .beta.-galactosidase, a chromogenic .beta.-glucuronidase substrate capable of forming an insoluble precipitate of a second color contrasting with said first color upon reacting with .beta.-glucuronidase, and a nutrient base medium wherein said indolyl .beta.-galactosidase is at least one selected from the group consisting of 6-chloroindolyl .beta.-D-galactoside, 4,6-dichloroindolyl-.beta.-D-galactoside, 6,7-dichloroindolyl-.beta.-D-galactoside, 4,6,7-trichloroindolyl-.beta.-D-galactoside and salts thereof,
• incubating said test medium to produce colonies of general coliforms and E. coli and said first and second colored precipitates corresponding to said colonies, and enumerating said colonies.

A method for detecting the presence of E. coli having .beta.-glucuronidase activity in a test sample, said method comprising the steps of

• inoculating a test medium with said test sample to be tested for the presence of microorganisms, said test medium being a solid or a liquid capable of forming a solid comprising a chromogenic indolyl .beta.-glucuronidase substrate capable of forming an insoluble precipitate upon reacting with .beta.-glucuronidase, and a nutrient base medium, wherein said indolyl .beta.-glucuronidase is at least one selected from the group consisting of 6-chloroindolyl-.beta.-D-glucuronide, 4,6-dichloroindolyl-.beta.-D-glucuronide, 6,7-dichloroindolyl-.beta.-D-glucuronide, 4,6,7-trichloroindolyl-.beta.-D-glucuronide and salts thereof,
• solidifying said test medium when said test medium is a liquid,
• incubating said test medium to produce colonies of E. coli and enumerating said colonies.

A method for detecting the presence of general coliforms having .beta.-galactosidase but not .beta.-glucuronidase activity, said method comprising the steps of

• inoculating a test medium with a sample to be tested for the presence of microorganisms, said test medium being a solid or a liquid capable of forming a solid comprising a chromogenic indolyl .beta.-galactosidase substrate capable of forming an insoluble precipitate of a first color upon reacting with .beta.-galactosidase, and a nutrient base medium, wherein said indolyl .beta.-galactosidase substrate is at least one selected from the group consisting of 6-chloroindolyl .beta.-D-galactoside, 4,6-dichloroindolyl-.beta.-D-galactoside, 6,7-dichloroindolyl-.beta.-D-galactoside, 4,6,7-trichloroindolyl-.beta.-D-galactoside and salts thereof,
• solidifying said test medium when said test medium is a liquid, and
• incubating said test medium to produce colonies of said coliforms and enumerating said colonies.