Primary Chromogenic Coliform Agar (CCA)

///Primary Chromogenic Coliform Agar (CCA)

Primary Chromogenic Coliform Agar (CCA)

Chromogenic Coliform Agar (CCA)
Chromogenic Coliform Agar (CCA) conforms to the ISO 9308-1 guidelines for the detection, enumeration and isolation of coliforms and more specifically Escherichia coli in water samples by the membrane-filtration technique. The colonial differentiation is provided by the chromogenic substrates, Salmon-GAL and X-glucuronide. Salmon-GAL is used for the detection of β-D-galactosidase enzymatic activity. X-glucuronide is used for the detection of β-D-Glucoronidase enzymatic activity. β-D-galactosidase, expressed by all coliforms, cleaves the Salmon-GAL substrate and producing red/pink coloured colonies. Unlike other coliforms, Escherichia coli leaves both Salmon-GAL and X-glucuronide producing a violet/blue coloured colonies. Tryptophan is used to increase detection reliability by improving the indole reaction. The peptones, sodium pyruvate and sorbitol support bacterial growth and simple recovery of sub-lethal thermally injured coliforms. Sodium di-hydrogen phosphate and di-sodium hydrogen phosphate phosphate buffer the medium and sodium chloride is used to achieve osmotic balance. The selectivity is attained by the addition of Tergitol® 7 as it inhibits the growth of Gram positive bacteria.

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Organisms Ref. No Result
Klebsiella aerogenes NCTC 10006 Red / pink colonies
Enterococcus faecalis NCTC 12697 Inhibited
Escherichia coli NCTC 12241 Violet / blue colonies
Pseudomonas aeruginosa NCTC 12903 Colourless colonies